Hypercholesterolemia: Stokes KY

Stokes KY. · Department of Molecular and Cellular Physiology, LSU Health Sciences Center, Shreveport, LA 71130, USA. · Antioxid Redox Signal. · Pubmed #16910762 No free full text.

Abstract: Hypercholesterolemia is recognized as one of the major risk factors in cardiovascular disease. It promotes the development of a proinflammatory phenotype in large vessels, in particular arteries, with disease. Cells of the innate and adaptive immune system are localized within atherosclerotic plaques and participate in the initiation and progression of plaque formation. It is now recognized that each segment of the microvasculature also experiences inflammation due to hypercholesterolemia, and that this occurs long before events in the large vessels. More recently, it is has been established that the innate and adaptive immune systems participate in the responses of postcapillary venules, and possibly arterioles, to elevated cholesterol levels, and that T lymphocytes may be one of the early cell types activated by hypercholesterolemia. These cells initiate a series of steps that lead to leukocyte accumulation in postcapillary venules and endothelial dysfunction in the arterioles. This review discusses the microvascular alterations induced by hypercholesterolemia, with particular attention paid to the roles of the innate and adaptive immune responses, and how these two systems may communicate to induce the microvascular inflammation.

Stokes KY, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA. · Expert Rev Cardiovasc Ther. · Pubmed #16292997 No free full text.

Abstract: Ischemic diseases are a leading cause of death worldwide. It is becoming increasingly appreciated that atherosclerosis is a major cause of ischemia reperfusion. Hypercholesterolemia is a major risk factor for the development of atherosclerosis, and is associated with an increased incidence of ischemia reperfusion. Furthermore, elevated cholesterol levels exacerbate the vascular responses to ischemia-reperfusion, which intensifies the resulting organ dysfunction. One of the underlying features of both ischemia-reperfusion injury and hypercholesterolemia is the proinflammatory and prothrombogenic phenotype invoked in the microvasculature. This is manifested as an endothelial dysfunction, characterized by leukocyte and platelet recruitment, oxidative stress and angiotensin II receptor Type 1a activation. These common pathways of inflammation offer attractive targets for the development of drugs to combat cardiovascular disease and the associated ischemic disorders.

Cooper D, Stokes KY, Tailor A, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA. · Cardiovasc Toxicol. · Pubmed #12665663 No free full text.

Abstract: Oxidative stress occurs when the production of reactive oxygen species (ROS) exceeds the capacity of the cell to detoxify these potentially injurious oxidants using endogenous antioxidant defense systems. Conditions associated with oxidative stress include ischemia/reperfusion, hypercholesterolemia, diabetes, and hypertension. The adhesion of circulating blood cells (leukocytes, platelets) to vascular endothelium is a key element of the pro-inflammatory and prothrombogenic phenotype assumed by the vasculature in these and other disease states that are associated with an oxidative stress. There is a growing body of evidence that links the blood cell endothelial cell interactions in these conditions to the enhanced production of ROS. Potential enzymatic sources of ROS within the microcirculation include xanthine oxidase, NAD(P)H oxidase, and nitric oxide synthase. ROS can promote a pro-inflammatory/prothrombogenic phenotype within the microvasculature by a variety of mechanisms, including the inactivation of nitric oxide, the activation of redox-sensitive transcription factors (e.g., nuclear factor-kappaB) that govern the expression of endothelial cell adhesion molecules (e.g., P-selectin), and the activation of enzymes (e.g., phospholipase A(2)) that produce leukocyte-stimulating inflammatory mediators (e.g., platelet-activating factor). The extensively documented ability of different oxidant-ablating interventions to attenuate blood cell endothelial cell interactions underscores the importance of ROS in mediating the dysfunctional microvascular responses to oxidative stress.

Stokes KY, Cooper D, Tailor A, Granger DN. · Department of Molecular and Cellular Physiology, LSU Health Sciences Center, Shreveport, LA 71130-3932, USA. · Free Radic Biol Med. · Pubmed #12374614 No free full text.

Abstract: Relatively brief periods (days) of hypercholesterolemia can exert profound effects on endothelium-dependent functions of the microcirculation, including dilation of arterioles, fluid filtration across capillaries, and regulation of leukocyte recruitment in postcapillary venules. Hypercholesterolemia appears to convert the normal anti-inflammatory phenotype of the microcirculation to a proinflammatory phenotype. This phenotypic change appears to result from a decline in nitric oxide (NO) bioavailability that results from a reduction in NO biosynthesis, inactivation of NO by superoxide (O(2)(*)(-)), or both. A consequence of the hypercholesterolemia-induced microvascular responses is an enhanced vulnerability of the microcirculation to the deleterious effects of ischemia and other inflammatory conditions. Hence, therapeutic strategies that are directed towards preventing the early microcirculatory dysfunction and inflammation caused by hypercholesterolemia may prove effective in reducing the high mortality associated with ischemic tissue diseases. Agents that act to maintain the normal balance between NO and reactive oxygen species (ROS) in vascular endothelial cells may prove particularly useful in this regard.

Granger DN, Stokes KY, Shigematsu T, Cerwinka WH, Tailor A, Krieglstein CF. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA. · Acta Physiol Scand. · Pubmed #11678730 No free full text.

Abstract: Reperfusion of ischaemic tissues often leads to microvascular dysfunction that is manifested as impaired endothelium-dependent dilation of arterioles, enhanced fluid filtration and leucocyte plugging in capillaries, and the trafficking of leucocytes and plasma protein extravasation in postcapillary venules. Efforts to define the mechanisms that underlie these microvascular responses to ischaemia and reperfusion have largely relied on pharmacological agents and monoclonal antibodies. Gene-targeting technology has been applied to the production of transgenic and knockout mice that are rapidly gaining acceptance as tools for mechanistic studies of ischaemia-reperfusion (I/R) injury that obviate some of the concerns (e.g. specificity) raised about previously employed experimental strategies. This review summarizes some of our efforts to apply gene-targeted mice to the study of I/R injury in the splanchnic vascular bed. A role for endothelial cell adhesion molecules (CAMs) and reactive oxygen metabolites is supported by results from mutant mice. Low density lipoprotein receptor mice also reveal that the microvascular and inflammatory responses to I/R are greatly exaggerated during chronic hypercholesterolaemia. The wide variety of mutant mice that have been produced for inflammation-related research makes this experimental strategy particularly promising for mechanistic investigations of the tissue responses to I/R.

Stokes KY, Dugas TR, Tang Y, Garg H, Guidry E, Bryan NS. · Department of Molecular and Cellular Physiology, Brown Foundation Institute of Molecular Medicine, The Univ. of Texas-Houston Health Science Center, 1825 Pressler St., SRB 530B, Houston, TX 77030, USA. · Am J Physiol Heart Circ Physiol. · Pubmed #19252084 No free full text.

Abstract: The nitrite anion is an endogenous product of mammalian nitric oxide (NO) metabolism, a key intermediate in the nitrogen cycle in plants, and a constituent of many foods. Research over the past 6 years has revealed surprising biological and cytoprotective activity of this anion. Hypercholesterolemia causes a proinflammatory phenotype in the microcirculation. This phenotype appears to result from a decline in NO bioavailability that results from a reduction in NO biosynthesis, inactivation of NO by superoxide, or both. Since nitrite has been shown to be potently cytoprotective and restore NO biochemical homeostasis, we investigated if supplemental nitrite could attenuate microvascular inflammation caused by a high cholesterol diet. C57Bl/6J mice were fed either a normal diet or a high cholesterol diet for 3 wk to induce microvascular inflammation. Mice on the high cholesterol diet received either nitrite-free drinking water or supplemental nitrite at 33 or 99 mg/l ad libitum in their drinking water. The results from this investigation reveal that mice fed a cholesterol-enriched diet exhibited significantly elevated leukocyte adhesion to and emigration through the venular endothelium as well as impaired endothelium-dependent relaxation in arterioles. Administration of nitrite in the drinking water inhibited the leukocyte adhesion and emigration and prevented the arteriolar dysfunction. This was associated with sparing of reduced tetrahydrobiopterin and decreased levels of C-reactive protein. These data reveal novel anti-inflammatory properties of nitrite and implicate the use of nitrite as a new natural therapy for microvascular inflammation and endothelial dysfunction associated with hypercholesterolemia.

Stokes KY, Calahan L, Hamric CM, Russell JM, Granger DN. · Dept. of Molecular and Cellular Physiology, LSU Health Sciences Ctr., 1501 E. Kings Hwy., Shreveport, LA 71130-3932, USA. · Am J Physiol Heart Circ Physiol. · Pubmed #19112095 No free full text.

Abstract: Hypercholesterolemia is associated with phenotypic changes in endothelial cell function that lead to a proinflammatory and prothrombogenic state in different segments of the microvasculature. CD40 ligand (CD40L) and its receptor CD40 are ubiquitously expressed and mediate inflammatory responses and platelet activation. The objective of this study was to determine whether CD40/CD40L, in particular T-cell CD40L, contributes to microvascular dysfunction induced by hypercholesterolemia. Intravital microscopy was used to quantify blood cell adhesion in cremasteric postcapillary venules, endothelium-dependent vasodilation responses in arterioles, and microvascular oxidative stress in wild-type (WT) C57BL/6, CD40-deficient ((-/-)), CD40L(-/-), or severe combined immune deficient (SCID) mice placed on a normal (ND) or high-cholesterol (HC) diet for 2 wk. WT-HC mice exhibited an exaggerated leukocyte and platelet recruitment in venules and impaired vasodilation responses in arterioles compared with ND counterparts. A deficiency of CD40, CD40L, or lymphocytes attenuated these responses to HC. The HC phenotype was rescued in CD40L(-/-) and SCID mice by a transfer of WT T cells. Bone marrow chimeras revealed roles for both vascular- and blood cell-derived CD40 and CD40L in the HC-induced vascular responses. Hypercholesterolemia induced an oxidative stress in both arterioles and venules of WT mice, which was abrogated by either CD40 or CD40L deficiency. The transfer of WT T cells into CD40L(-/-) mice restored the oxidative stress. These results implicate CD40/CD40L interactions between circulating cells and the vascular wall in both the arteriolar and venular dysfunction elicited by hypercholesterolemia and identify T-cell-associated CD40L as a key mediator of these responses.

Wolfort RM, Stokes KY, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA. · Am J Physiol Heart Circ Physiol. · Pubmed #18408127 links to  free full text

Abstract: Although hypercholesterolemia is known to impair endothelium-dependent vasodilation (EDV) long before the appearance of atherosclerotic plaques, it remains unclear whether the immune mechanisms that have been implicated in atherogenesis also contribute to the early oxidative stress and endothelial cell dysfunction elicited by hypercholesterolemia. EDV (wire myography), superoxide generation (cytochrome c reduction), and NAD(P)H oxidase mRNA expression were monitored in aortic rings from wild-type (WT) and mutant mice placed on either a normal diet or a cholesterol-enriched diet (HC) for 2 wk. WT mice on HC exhibited impaired EDV, enhanced superoxide generation, and increased expression of NAD(P)H oxidase subunit Nox-2 mRNA. The impaired EDV and increased superoxide generation induced by HC were significantly blunted in severe combined immunodeficient (SCID) mice and CD4+ T lymphocyte-deficient mice. These responses were also attenuated in HC mice genetically deficient in IFN-gamma; however, adoptive transfer of WT-HC CD4+ T lymphocytes to IFN-gamma-deficient recipients restored HC-induced responses. The HC-induced impaired EDV and oxidative stress were also attenuated in HC mice genetically deficient in Nox-2 (gp91(phox-/-)) and in WT-->gp91(phox-/-)-HC chimeras. HC-induced gp91(phox) mRNA expression was significantly blunted in mice deficient in CD4+ T cells or IFN-gamma and was restored with adoptive transfer of WT-HC CD4+ T cells to IFN-gamma-deficient recipients. These findings implicate the immune system in the early endothelial cell dysfunction associated with hypercholesterolemia and are consistent with a mechanism of impaired EDV that is mediated by CD4+ T cells and IFN-gamma, acting through the generation of superoxide from vascular NAD(P)H oxidase.

Stokes KY, Gurwara S, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, 1501 E Kings Highway, Shreveport, LA 71130-3932, USA. · Arterioscler Thromb Vasc Biol. · Pubmed #17585067 links to  free full text

Abstract: OBJECTIVES: T-lymphocytes and interferon-gamma (IFN-gamma) contribute to leukocyte recruitment in postcapillary venules during hypercholesterolemia. Our objectives were to determine whether: (1) T-lymphocytes are the source of this IFN-gamma, and (2) whether T-cell-derived IFN-gamma also mediates the accompanying arteriolar dysfunction and platelet adhesion. METHODS AND RESULTS: Intravital videomicroscopy was used to quantify arteriolar responses to acetylcholine, and leukocyte and platelet adhesion in postcapillary venules of wild-type (WT), immunodeficient (SCID), and IFN-gamma(-/-) mice on a normal (ND) or high-cholesterol (HC) diet. Acetylcholine-induced arteriolar dilation was impaired in WT-HC, compared with WT-ND. This endothelial dysfunction was absent in SCID-HC or IFN-gamma(-/-)-HC mice. Vasodilation was impaired by transfer of WT, but not IFN-gamma(-/-), T-cells to these immunodeficient mice. WT-HC mice exhibited elevated leukocyte and platelet adhesion in venules, versus WT-ND. This blood cell recruitment was attenuated to ND levels in SCID-HC and IFN-gamma(-/-)-HC mice, but restored to WT-HC levels by transfer of WT, but not IFN-gamma(-/-), T-lymphocytes. CONCLUSIONS: These data reveal a novel role of T-lymphocyte-derived IFN-gamma in the development of endothelial dysfunction in arterioles during hypercholesterolemia and extend our previous observations that IFN-gamma mediates both inflammatory and thrombogenic responses to hypercholesterolemia in postcapillary venules.

Stokes KY, Russell JM, Jennings MH, Alexander JS, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA. · Free Radic Biol Med. · Pubmed #17561090 links to  free full text

Abstract: Elevated cholesterol levels promote proinflammatory and prothrombogenic responses in venules and impaired endothelium-dependent arteriolar dilation. Although NAD(P)H oxidase-derived superoxide has been implicated in the altered vascular responses to hypercholesterolemia, it remains unclear whether this oxidative pathway mediates the associated arteriolar dysfunction and platelet adhesion in venules. Platelet and leukocyte adhesion in cremasteric postcapillary venules and arteriolar dilation responses to acetylcholine were monitored in wild-type (WT), Cu,Zn-superoxide dismutase transgenic (SOD-TgN), and NAD(P)H oxidase-knockout (gp91(phox-/-)) mice placed on a normal (ND) or high-cholesterol (HC) diet for 2 weeks. HC elicited increased platelet and leukocyte adhesion in WT mice versus ND. Cytosolic subunits of NAD(P)H oxidase (p47phox and p67phox) were expressed in platelets. This was not altered by hypercholesterolemia; however, platelets and leukocytes from HC mice exhibited elevated generation of reactive oxygen species compared to ND mice. Hypercholesterolemia-induced leukocyte recruitment was attenuated in SOD-TgN-HC and gp91(phox-/-)-HC mice. Recruitment of platelets derived from WT-HC mice in venules of SOD-TgN-HC or gp91(phox-/-)-HC recipients was comparable to ND levels. Adhesion of SOD-TgN-HC platelets paralleled the leukocyte response and was attenuated in SOD-TgN-HC recipients, but not in WT-HC recipients. However, gp91(phox-/-)-HC platelets exhibited low levels of adhesion comparable to those of WT-ND in both hypercholesterolemic gp91(phox-/-) and WT recipients. Arteriolar dysfunction was evident in WT-HC mice, compared to WT-ND. Overexpression of SOD or, to a lesser extent, gp91(phox) deficiency restored arteriolar vasorelaxation responses toward WT-ND levels. These findings reveal a novel role for platelet-associated NAD(P)H oxidase in producing the thrombogenic phenotype in hypercholesterolemia and demonstrate that NAD(P)H oxidase-derived superoxide mediates the HC-induced arteriolar dysfunction.

Stokes KY, Calahan L, Russell JM, Gurwara S, Granger DN. · Department of Molecular and Cellular Physiology, LSU Health Sciences Center, Shreveport, Louisiana 71130-3932, USA. · Microcirculation. · Pubmed #16815823 No free full text.

Abstract: OBJECTIVE: To define the contribution of platelets, specifically platelet-associated P-selectin, to the altered venular and arteriolar responses induced by hypercholesterolemia. METHODS: Leukocyte and platelet recruitment in cremasteric venules, and endothelium-dependent relaxation (EDR) in arterioles were determined using intravital videomicroscopy. Wild-type (WT) mice were placed on a normal or high cholesterol diet. Hypercholesterolemic mice were treated with blocking antibodies against either P-selectin or PSGL-1, or were depleted of neutrophils (ANS) or platelets (APS). Bone marrow chimeras (P-selectin deficiency in platelets, but not in endothelial cells) were produced by transplanting bone marrow from P-selectin-/- into WT mice (P-sel-/---> WT). RESULTS: Hypercholesterolemia (HC) elicited the recruitment of adherent platelets and leukocytes in venules and an impaired EDR in arterioles. The exaggerated cell adhesion responses were absent in hypercholesterolemic mice treated with ANS, anti-P-selectin or anti-PSGL-1 antibodies and in P-sel-/---> WT chimeras. The hypercholesterolemia-induced impairment of arteriolar EDR was significantly blunted in mice rendered either neutropenic or thrombocytopenic, and in P-sel-/---> WT chimeras. CONCLUSIONS: The findings indicate that platelet-associated P-selectin contributes to the recruitment of leukocytes and platelets in venules of hypercholesterolemic mice and that the P-selectin-mediated adhesive interactions also contribute to the impaired arteriolar function induced by hypercholesterolemia.

Petnehazy T, Stokes KY, Wood KC, Russell J, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University, Health Sciences Center, Shreveport, LA 71130-3932, USA. · Arterioscler Thromb Vasc Biol. · Pubmed #16254200 links to  free full text

Abstract: OBJECTIVE: Hypercholesterolemia elicits a proinflammatory and prothrombogenic phenotype in the microvasculature that is characterized by activation and adhesion of blood cells. The angiotensin II receptor-1 antagonist Losartan prevents the induction of these responses. The objective of this study was to determine the relative contributions of blood cell-associated versus endothelium-associated AT1a-R to these hypercholesterolemia-induced microvascular alterations. METHODS AND RESULTS: Leukocyte adhesion and emigration and platelet adhesion were quantified by intravital microscopy in postcapillary venules. C57Bl/6 mice were placed on a normal (ND) or high-cholesterol (HCD) diet for 2 weeks. AT1a-R bone marrow chimeras that express AT1a-R on the vessel wall but not blood cells and AT1a-R knockouts were placed on HCD. Venular shear rate was comparable in all groups. Platelet and leukocyte adhesion and leukocyte emigration were significantly increased in HCD mice versus ND. Leukocyte recruitment was significantly reduced in the HCD-AT1a-R bone marrow chimera group, whereas platelet adhesion remained at HCD levels. However, in HCD-AT1a-R knockout mice, platelet and leukocyte adhesion were reduced to ND levels. CONCLUSIONS: These data indicate that the platelet-vessel wall adhesion elicited by hypercholesterolemia is mediated by AT1a-R engagement on the endothelial cell rather than the platelet, whereas leukocyte recruitment is mediated by blood cell-associated AT1a-R.

Petnehazy T, Stokes KY, Russell JM, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, 1501 E Kings Highway, Shreveport, LA 71130-3932, USA. · Hypertension. · Pubmed #15655122 links to  free full text

Abstract: Hypercholesterolemia elicits an inflammatory response in the microvasculature that is accompanied by an increased expression of angiotensin II type-1 receptors (AT1-R) on platelets, leukocytes, and endothelial cells. AT1-R blockade attenuates inflammatory responses to angiotensin II (eg, adhesion molecule expression and reactive oxygen species production). We investigated whether AT1-R antagonism attenuates the platelet and leukocyte recruitment induced by acute hypercholesterolemia in postcapillary venules. Leukocyte and platelet adhesion and oxidative stress were quantified by intravital microscopy in cremaster muscle, and P-selectin and AT1-R expression was determined in mice placed on a normal diet (ND) or high-cholesterol diet (HCD) for 2 weeks. Platelet and leukocyte adhesion was significantly elevated by hypercholesterolemia. In HCD mice receiving losartan (HCD-Los) in drinking water, platelet and leukocyte recruitment was reduced to ND levels. Increased platelet adhesion was observed in HCD mice receiving platelets from HCD-Los mice, consistent with a direct beneficial action of losartan on the vessel wall. Hypercholesterolemia elicited an oxidative stress in venules and an increased expression of P-selectin and AT1-R. The oxidative stress and AT1-R upregulation were reduced by losartan, but the P-selectin response was not. We propose that AT1-R engagement contributes to the prothrombogenic and proinflammatory state induced in venules by hypercholesterolemia.

Stokes KY, Granger DN. · Department of Molecular & Cellular Physiology, LSU Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA. · J Physiol. · Pubmed #15611017 links to  free full text

Abstract: There is abundant evidence that links hypercholesterolaemia to both vascular inflammation and atherogenesis. While atherosclerosis is a large vessel disease that is characterized by leucocyte infiltration and lipid deposition in the wall of lesion-prone arteries, the inflammatory response does not appear to be confined to these locations. There is evidence supporting a systemic inflammatory response that is characterized by endothelial cell activation in multiple vascular beds and the appearance of activated immune cells and a wide range of inflammatory mediators in blood. The mechanism(s) responsible for initiating this systemic response remain poorly defined, although several inciting factors have been proposed, including infectious agents and oxidative stress resulting from one or more of the cardiovascular risk factors (e.g. hypercholesterolaemia, hypertension). While cells within lesion-prone arteries are often inferred as the source of circulating inflammatory mediators during atherogenesis, the fact that endothelial cells throughout the vasculature are activated raises the possibility that the microvasculature (which encompasses a vast endothelial surface area) may contribute to creating the systemic inflammatory milieu that is linked to atherogenesis. This review addresses evidence that links the microvasculature to the inflammatory responses induced by hypercholesterolaemia and offers the hypothesis that inflammatory events initiated within the microcirculation may contribute to initiation and/or progression of large vessel disease.

Ishikawa M, Stokes KY, Zhang JH, Nanda A, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, La 71130-3932, USA. · Circ Res. · Pubmed #14670846 links to  free full text

Abstract: Although hypercholesterolemia is widely accepted as a major risk factor for coronary artery and peripheral vascular diseases, its role in the pathogenesis of stroke is controversial. The objectives of this study were to determine how hypercholesterolemia affects the cerebral microcirculation under resting conditions and after ischemia-reperfusion (I/R). Platelet- and leukocyte-endothelial cell interactions and oxidant production (using the oxidant-sensitive fluorochrome dihydrorhodamine-123) were monitored by intravital videomicroscopy in the cerebral microvasculature of mice placed on either a normal (ND) or cholesterol-enriched diet (HCD). Platelets labeled with carboxyfluorescein diacetate succinimidyl ester (CFDASE) and leukocytes labeled with rhodamine 6G were seen to roll and firmly adhere, with a corresponding increase in oxidant production, in venules of mice on HCD, but not ND. Immunoneutralization of P-selectin attenuated the platelet- and leukocyte-endothelial cell interactions and the enhanced oxidant production associated with HCD. A GPIIb/IIIa blocking antibody did not alter the blood cell-vessel wall interactions to HCD. Mice deficient in the NADPH oxidase subunit gp91(phox) exhibited significantly blunted platelet and leukocyte recruitment responses to HCD. Focal I/R also elicited inflammatory and prothrombogenic responses in cerebral venules and these were exaggerated in mice on HCD. These results implicate an oxidant-dependent, P-selectin-mediated mechanism in the blood cell-vessel wall interactions induced by hypercholesterolemia in the brain and demonstrate that the deleterious effects of I/R on the brain are exacerbated by this cardiovascular risk factor.

Stokes KY, Clanton EC, Gehrig JL, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, 1501 E. Kings Highway, Shreveport, LA 71130-3932, USA. · Am J Physiol Heart Circ Physiol. · Pubmed #12907426 links to  free full text

Abstract: We have previously shown that T lymphocytes and interferon-gamma are involved in hypercholesterolemia-induced leukocyte adhesion to vascular endothelium. This study assessed the contribution of interleukin 12 (IL-12) to these hypercholesterolemia-induced inflammatory responses. Intravital videomicroscopy was used to quantify leukocyte adhesion and emigration and oxidant stress (dihydrorhodamine oxidation) in unstimulated cremasteric venules (wall shear rate > or =500 s-1) of wild-type (WT) C57Bl/6, lymphocyte-deficient [recombinase-activating gene knockout (RAG1-/-)], and IL-12-deficient (p35-/- and p40-/-; p35 and p40 are the two subunits of active IL-12) mice on either a normal (ND) or high-cholesterol (HC) diet for 2 wk. RAG1-/--HC mice received splenocytes from WT-HC (WT --> RAG1-/-), p35-/--HC (p35-/- --> RAG1-/-), or p40-/--HC (p40-/- --> RAG1-/-) mice. Compared with WT-ND mice, WT-HC mice exhibited exaggerated leukocyte adherence and emigration as well as increased dihydrorhodamine oxidation. The enhanced leukocyte recruitment was absent in the RAG1-/--ND, p35-/--ND, and p40-/--ND groups. Hypercholesterolemia-induced leukocyte adherence and emigration were attenuated in RAG1-/--HC vs. WT-HC mice but were similar to ND mice. Furthermore, compared with WT-HC animals, p35-/--HC and p40-/--HC mice showed significantly lower leukocyte adhesion and tissue oxidant stress responses, but these values were comparable to ND mice. Leukocyte adherence and emigration in WT --> RAG1-/- mice were similar to responses of WT-HC mice. However, p35-/- --> RAG1-/- mice had lower levels of adherence and emigration vs. the WT --> RAG1-/- and WT-HC groups. Elevated levels of leukocyte adherence and emigration were restored by approximately 50% toward WT-HC levels in p40-/- --> RAG1-/- mice. These findings implicate IL-12 in the inflammatory responses observed in the venules of hypercholesterolemic mice.

Stokes KY, Clanton EC, Clements KP, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, 1501 E Kings Highway, Shreveport, La 71130-3932, USA. · Circulation. · Pubmed #12695304 links to  free full text

Abstract: BACKGROUND: A T-cell-mediated inflammatory response occurs in the microcirculation during acute hypercholesterolemia. The objective of this study was to define the contribution of T-lymphocyte-derived interferon-gamma (IFN-gamma) to the leukocyte-endothelial cell adhesion induced by hypercholesterolemia. METHODS AND RESULTS: Intravital videomicroscopy was used to quantify the adhesion and emigration of leukocytes and oxidant stress (dihydrorhodamine [DHR] oxidation) in cremasteric venules. Wild-type (WT), IFN-gamma-/-, and severe combined immunodeficiency (SCID) mice were placed on either a normal (ND) or high-cholesterol (HC) diet for 2 weeks. WT-HC mice exhibited exaggerated adhesion and emigration of leukocytes and enhanced DHR oxidation compared with WT-ND. The exaggerated adhesion responses and increased DHR oxidation were not seen in IFN-gamma-/--HC mice. SCID-HC mice also exhibited attenuated inflammatory responses compared with WT-HC. Reconstitution of either SCID-HC or IFN-gamma-/--HC mice with WT-HC splenocytes restored the inflammatory responses, whereas reconstitution of SCID-HC with IFN-gamma-/--HC splenocytes did not. The HC-induced oxidant stress was restored in IFN-gamma-/--HC mice reconstituted with WT-HC splenocytes. CONCLUSIONS: These findings implicate IFN-gamma as a cause of the inflammatory phenotype that is assumed by the microvasculature of hypercholesterolemic mice and suggest that T lymphocytes are a major source of this proinflammatory cytokine.

Stokes KY, Clanton EC, Bowles KS, Fuseler JW, Chervenak D, Chervenak R, Jennings SR, Granger DN. · Department of Molecular and Cellular Physiology, LSU Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA. · Microcirculation. · Pubmed #12375178 No free full text.

Abstract: OBJECTIVE: Hypercholesterolemia promotes the adhesion of leukocytes to vascular endothelium in large and microscopic blood vessels. Lymphocytes that can modulate endothelial cell adhesion molecule expression have been implicated in the altered structure and function of large arterial vessels associated with chronic hypercholesterolemia. This study assesses the contribution of CD4(+) and CD8(+) T-cells to acute inflammatory responses observed in the microcirculation of hypercholesterolemic mice. METHODS: Intravital microscopy was used to quantify baseline leukocyte-endothelial cell interactions in cremasteric postcapillary venules of wild-type (WT) and severe combined immunodeficient (SCID) mice placed on a normal (ND) or high-cholesterol (HC) diet for 2 weeks. A group of SCID-HC mice received splenocytes from WT-HC mice (WT-->SCID). Separate WT-HC groups were depleted of neutrophils or CD4(+) and/or CD8(+) T-cells. RESULTS: WT-HC mice, compared with WT-ND, exhibited exaggerated leukocyte adherence and emigration. These leukocytes were predominantly granulocytes. These responses were absent in neutropenic WT-HC mice. SCID-HC mice also showed significantly less leukocyte adherence and emigration than WT-HC mice. Elevated leukocyte adherence and emigration were restored in WT-->SCID mice, despite a continued absence of circulating blood lymphocytes. Selective depletion of either CD4(+) or CD8(+) cell populations attenuated HC-induced leukocyte adhesion but not emigration. However, simultaneous depletion of both CD4(+) and CD8(+) cells attenuated both leukocyte adhesion and emigration to ND levels. DISCUSSION: These findings indicate that both CD4(+) and CD8(+) T-cells contribute to granulocyte adhesion and emigration elicited in postcapillary venules by hypercholesterolemia.

Stokes KY, Clanton EC, Russell JM, Ross CR, Granger DN. · Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA, USA. · Circ Res. · Pubmed #11249873 links to  free full text

Abstract: Experimental animals placed on a high-cholesterol diet for 2 or more weeks exhibit an inflammatory response in postcapillary venules. The aims of this study were to determine (1) whether superoxide mediates the hypercholesterolemia-induced inflammatory response and (2) whether leukocyte and/or vessel wall NAD(P)H oxidase contributes to this response. Intravital videomicroscopy was used to quantify leukocyte-endothelial cell adhesion in cremasteric postcapillary venules of wild-type (WT) mice, CuZn-superoxide dismutase transgenic (SOD TgN) mice, and mice heterozygous (p47(phox)+/-) or homozygous (p47(phox)-/-) for NAD(P)H oxidase placed on either a normal diet or high-cholesterol diet (HCD) for 2 weeks. The number of adherent and emigrated leukocytes in postcapillary venules of WT HCD mice was significantly higher than that detected in venules of their normal-diet counterparts. However, the HCD-induced recruitment of adherent and emigrated leukocytes was not observed in SOD TgN mice. Whereas hypercholesterolemic p47(phox)+/- and WT mice exhibited similar inflammatory responses, p47(phox)-/- mice did not. Bone marrow chimeras were developed to selectively delete p47(phox) from either the vessel wall or circulating leukocytes. Whereas WT marrow transplanted into WT mice produced a normal inflammatory response of venules to HCD, chimeric mice with p47(phox) deficiency in either the vessel wall or leukocytes exhibited an attenuated inflammatory response to HCD that was comparable with that observed in p47(phox)-/- HCD mice. Our findings indicate that enhanced superoxide production is a critical event that initiates the leukocyte-endothelial cell adhesion in postcapillary venules of HCD mice. NAD(P)H oxidase appears to be an important source of this superoxide.

Wolfort RM, Stokes KY, Granger DN. · No affiliation provided · Am J Physiol Heart Circ Physiol. · Pubmed #18775849 No free full text.

This publication has no abstract.