Deficiency of Prebiotic Fiber and Insufficient Signaling Through Gut Metabolite-Sensing Receptors Leads to Cardiovascular Disease.

BACKGROUND: High blood pressure (BP) continues to be a major, poorly controlled but modifiable risk factor for cardiovascular death. Among key Western lifestyle factors, a diet poor in fiber is associated with prevalence of high BP. The impact of lack of prebiotic fiber and the associated mechanisms that lead to higher BP are unknown. Here we show that lack of prebiotic dietary fiber leads to the development of a hypertensinogenic gut microbiota, hypertension and its complications, and demonstrate a role for G-protein coupled-receptors (GPCRs) that sense gut metabolites. METHODS: One hundred seventy-nine mice including C57BL/6J, gnotobiotic C57BL/6J, and knockout strains for GPR41, GPR43, GPR109A, and GPR43/109A were included. C57BL/6J mice were implanted with minipumps containing saline or a slow-pressor dose of angiotensin II (0.25 mg·kg-1·d-1). Mice were fed diets lacking prebiotic fiber with or without addition of gut metabolites called short-chain fatty acids ([SCFA)] produced during fermentation of prebiotic fiber in the large intestine), or high prebiotic fiber diets. Cardiac histology and function, BP, sodium and potassium excretion, gut microbiome, flow cytometry, catecholamines and methylation-wide changes were determined. RESULTS: Lack of prebiotic fiber predisposed mice to hypertension in the presence of a mild hypertensive stimulus, with resultant pathological cardiac remodeling. Transfer of a hypertensinogenic microbiota to gnotobiotic mice recapitulated the prebiotic-deprived hypertensive phenotype, including cardiac manifestations. Reintroduction of SCFAs to fiber-depleted mice had protective effects on the development of hypertension, cardiac hypertrophy, and fibrosis. The cardioprotective effect of SCFAs were mediated via the cognate SCFA receptors GPR43/GPR109A, and modulated L-3,4-dihydroxyphenylalanine levels and the abundance of T regulatory cells regulated by DNA methylation. CONCLUSIONS: The detrimental effects of low fiber Westernized diets may underlie hypertension, through deficient SCFA production and GPR43/109A signaling. Maintaining a healthy, SCFA-producing microbiota is important for cardiovascular health.

Effects of high- and low-dose aspirin on adaptive immunity and hypertension in the stroke-prone spontaneously hypertensive rat.

Despite its well-known antithrombotic properties, the effect of aspirin on blood pressure (BP) and hypertension pathology is unclear. The hugely varying doses used clinically have contributed to this confusion, with high-dose aspirin still commonly used due to concerns about the efficacy of low-dose aspirin. Because prostaglandins have been shown to both promote and inhibit T-cell activation, we also explored the immunomodulatory properties of aspirin in hypertension. Although the common preclinical high dose of 100 mg/kg/d improved vascular dysfunction and cardiac hypertrophy, this effect was accompanied by indices of elevated adaptive immunity, renal T-cell infiltration, renal fibrosis, and BP elevation in stroke-prone spontaneously hypertensive rats and in angiotensin II-induced hypertensive mice. The cardioprotective effects of aspirin were conserved with a lower dose (10 mg/kg/d) while circumventing heightened adaptive immunity and elevated BP. We also show that low-dose aspirin improves renal fibrosis. Differential inhibition of the COX-2 isoform may underlie the disparate effects of the 2 doses. Our results demonstrate the efficacy of low-dose aspirin in treating a vast array of cardiovascular parameters and suggest modulation of adaptive immunity as a novel mechanism underlying adverse cardiovascular profiles associated with COX-2 inhibitors. Clinical studies should identify the dose of aspirin that achieves maximal cardioprotection with a new awareness that higher doses of aspirin could trigger undesired autoimmunity in hypertensive individuals. This work also warrants an evaluation of high-dose aspirin and COX-2 inhibitor therapy in sufferers of inflammatory conditions who are already at increased risk for cardiovascular disease.-Khan, S. I., Shihata, W. A., Andrews, K. L., Lee, M. K. S., Moore, X.-L., Jefferis, A.-M., Vinh, A., Gaspari, T., Dragoljevic, D., Jennings, G. L., Murphy, A. J., Chin-Dusting, J. P. F. Effects of high- and low-dose aspirin on adaptive immunity and hypertension in the stroke-prone spontaneously hypertensive rat.

Chronic sympathetic driven hypertension promotes atherosclerosis by enhancing hematopoiesis.

Hypertension is a major, independent risk factor for atherosclerotic cardiovascular disease. However, this pathology can arise through multiple pathways, which could influence vascular disease through distinct mechanisms. An overactive sympathetic nervous system is a dominant pathway that can precipitate in elevated blood pressure. We aimed to determine how the sympathetic nervous system directly promotes atherosclerosis in the setting of hypertension. We used a mouse model of sympathetic nervous system-driven hypertension on the atherosclerotic-prone apolipoprotein E-deficient background. When mice were placed on a western type diet for 16 weeks, we showed the evolution of unstable atherosclerotic lesions. Fortuitously, the changes in lesion composition were independent of endothelial dysfunction, allowing for the discovery of alternative mechanisms. With the use of flow cytometry and bone marrow imaging, we found that sympathetic activation caused deterioration of the hematopoietic stem and progenitor cell niche in the bone marrow, promoting the liberation of these cells into the circulation and extramedullary hematopoiesis in the spleen. Specifically, sympathetic activation reduced the abundance of key hematopoietic stem and progenitor cell niche cells, sinusoidal endothelial cells and osteoblasts. Additionally, sympathetic bone marrow activity prompted neutrophils to secrete proteases to cleave the hematopoietic stem and progenitor cell surface receptor CXCR4. All these effects could be reversed using the ß-blocker propranolol during the feeding period. These findings suggest that elevated blood pressure driven by the sympathetic nervous system can influence mechanisms that modulate the hematopoietic system to promote atherosclerosis and contribute to cardiovascular events.

Defective cholesterol metabolism in haematopoietic stem cells promotes monocyte-driven atherosclerosis in rheumatoid arthritis.

Aim: Rheumatoid arthritis (RA) is associated with an approximately two-fold elevated risk of cardiovascular (CV)-related mortality. Patients with RA present with systemic inflammation including raised circulating myeloid cells, but fail to display traditional CV risk-factors, particularly dyslipidaemia. We aimed to explore if increased circulating myeloid cells is associated with impaired atherosclerotic lesion regression or altered progression in RA. Methods and results: Using flow cytometry, we noted prominent monocytosis, neutrophilia, and thrombocytosis in two mouse models of RA. This was due to enhanced proliferation of the haematopoietic stem and progenitor cells (HSPCs) in the bone marrow and the spleen. HSPCs expansion was associated with an increase in the cholesterol content, due to a down-regulation of cholesterol efflux genes, Apoe, Abca1, and Abcg1. The HSPCs also had enhanced expression of key myeloid promoting growth factor receptors. Systemic inflammation was found to cause defective cellular cholesterol metabolism. Increased myeloid cells in mice with RA were associated with a significant impairment in lesion regression, even though cholesterol levels were equivalent to non-arthritic mice. Lesions from arthritic mice exhibited a less stable phenotype as demonstrated by increased immune cell infiltration, lipid accumulation, and decreased collagen formation. In a progression model, we noted monocytosis, enhanced monocytes recruitment to lesions, and increased plaque macrophages. This was reversed with administration of reconstituted high-density lipoprotein (rHDL). Furthermore, RA patients have expanded CD16+ monocyte subsets and a down-regulation of ABCA1 and ABCG1. Conclusion: Rheumatoid arthritis impairs atherosclerotic regression and alters progression, which is associated with an expansion of myeloid cells and disturbed cellular cholesterol handling, independent of plasma cholesterol levels. Infusion of rHDL prevented enhanced myelopoiesis and monocyte entry into lesions. Targeting cellular cholesterol defects in people with RA, even if plasma cholesterol is within the normal range, may limit vascular disease.

NFκB Inhibition Mitigates Serum Amyloid A-Induced Pro-Atherogenic Responses in Endothelial Cells and Leukocyte Adhesion and Adverse Changes to Endothelium Function in Isolated Aorta.

The acute phase protein serum amyloid A (SAA) is associated with endothelial dysfunction and early-stage atherogenesis. Stimulation of vascular cells with SAA increases gene expression of pro-inflammation cytokines and tissue factor (TF). Activation of the transcription factor, nuclear factor kappa-B (NFκB), may be central to SAA-mediated endothelial cell inflammation, dysfunction and pro-thrombotic responses, while targeting NFκB with a pharmacologic inhibitor, BAY11-7082, may mitigate SAA activity. Human carotid artery endothelial cells (HCtAEC) were pre-incubated (1.5 h) with 10 µM BAY11-7082 or vehicle (control) followed by SAA (10 µg/mL; 4.5 h). Under these conditions gene expression for TF and Tumor Necrosis Factor (TNF) increased in SAA-treated HCtAEC and pre-treatment with BAY11-7082 significantly (TNF) and marginally (TF) reduced mRNA expression. Intracellular TNF and interleukin 6 (IL-6) protein also increased in HCtAEC supplemented with SAA and this expression was inhibited by BAY11-7082. Supplemented BAY11-7082 also significantly decreased SAA-mediated leukocyte adhesion to apolipoprotein E-deficient mouse aorta in ex vivo vascular flow studies. In vascular function studies, isolated aortic rings pre-treated with BAY11-7082 prior to incubation with SAA showed improved endothelium-dependent vasorelaxation and increased vascular cyclic guanosine monophosphate (cGMP) content. Together these data suggest that inhibition of NFκB activation may protect endothelial function by inhibiting the pro-inflammatory and pro-thrombotic activities of SAA.

Nitroxyl (HNO) reduces endothelial and monocyte activation and promotes M2 macrophage polarization.

Nitroxyl anion (HNO) donors are currently being assessed for their therapeutic utility in several cardiovascular disorders including heart failure. Here, we examine their effect on factors that precede atherosclerosis including endothelial cell and monocyte activation, leucocyte adhesion to the endothelium and macrophage polarization. Similar to the NO donor glyceryl trinitrate (GTN), the HNO donors Angeli's salt (AS) and isopropylamine NONOate (IPA/NO) decreased leucocyte adhesion to activated human umbilical vein endothelial cells (HUVECs) and mouse isolated aorta. This reduction in adhesion was accompanied by a reduction in intercellular adhesion molecule-1 (ICAM-1) and the cytokines monocyte chemoattractant protein 1 (MCP-1) and interleukin 6 (IL-6) which was inhibitor of nuclear factor κB (NFκB) α (IκBα)- and subsequently NFκB-dependent. Intriguingly, the effects of AS on leucocyte adhesion, like those on vasodilation, were found to not be susceptible to pharmacological tolerance, unlike those observed with GTN. As well, HNO reduces monocyte activation and promotes polarization of M2 macrophages. Taken together, our data demonstrate that HNO donors can reduce factors that are associated with and which precede atherosclerosis and may thus be useful therapeutically. Furthermore, since the effects of the HNO donors were not subject to tolerance, this confers an additional advantage over NO donors.

Influence of angiotensin II on the gut microbiome: Modest effects in comparison to experimental factors.

INTRODUCTION: Animal models are regularly used to test the role of the gut microbiome in hypertension. Small-scale pre-clinical studies have investigated changes to the gut microbiome in the angiotensin II hypertensive model. However, the gut microbiome is influenced by internal and external experimental factors which are not regularly considered in the study design. Once these factors are accounted for, it is unclear if microbiome signatures are reproduceable. We aimed to determine the influence of angiotensin II treatment on the gut microbiome using a large and diverse cohort of mice and to quantify the magnitude by which other factors contribute to microbiome variations. METHODS AND RESULTS: We conducted a retrospective study to establish a diverse mouse cohort resembling large human studies. We sequenced the V4 region of the 16S rRNA gene from 538 samples across the gastrointestinal tract of 303 male and female C57BL/6J mice randomised into sham or angiotensin II treatment from different genotypes, diets, animal facilities, and age groups. Analysing over 17 million sequencing reads, we observed that angiotensin II treatment influenced α-diversity (P = 0.0137) and ß-diversity (i.e., composition of the microbiome, P < 0.001). Bacterial abundance analysis revealed patterns consistent with a reduction in short-chain fatty acid-producers, microbial metabolites that lower blood pressure. Furthermore, animal facility, genotype, diet, age, sex, intestinal sampling site, and sequencing batch had significant effects on both α- and ß-diversity (all P < 0.001). Sampling site (6.8%) and diet (6%) had the largest impact on the microbiome, while angiotensin II and sex had the smallest effect (each 0.4%). CONCLUSIONS: Our large-scale data confirmed findings from small-scale studies that angiotensin II impacted the gut microbiome. However, this effect was modest relative to most of the other factors studied. Accounting for these factors in future pre-clinical hypertensive studies will increase the likelihood that microbiome findings are replicable and translatable.

Administration of an LXR agonist promotes atherosclerotic lesion remodelling in murine inflammatory arthritis.

Objectives: The leading cause of mortality in patients with rheumatoid arthritis is atherosclerotic cardiovascular disease (CVD). We have shown that murine arthritis impairs atherosclerotic lesion regression, because of cellular cholesterol efflux defects in haematopoietic stem and progenitor cells (HSPCs), causing monocytosis and impaired atherosclerotic regression. Therefore, we hypothesised that improving cholesterol efflux using a Liver X Receptor (LXR) agonist would improve cholesterol efflux and improve atherosclerotic lesion regression in arthritis. Methods: Ldlr -/- mice were fed a western-type diet for 14 weeks to initiate atherogenesis, then switched to a chow diet to induce lesion regression and divided into three groups; (1) control, (2) K/BxN serum transfer inflammatory arthritis (K/BxN) or (3) K/BxN arthritis and LXR agonist T0901317 daily for 2 weeks. Results: LXR activation during murine inflammatory arthritis completely restored atherosclerotic lesion regression in arthritic mice, evidenced by reduced lesion size, macrophage abundance and lipid content. Mechanistically, serum from arthritic mice promoted foam cell formation, demonstrated by increased cellular lipid accumulation in macrophages and paralleled by a reduction in mRNA of the cholesterol efflux transporters Abca1, Abcg1 and Apoe. T0901317 reduced lipid loading and increased Abca1 and Abcg1 expression in macrophages exposed to arthritic serum and increased ABCA1 levels in atherosclerotic lesions of arthritic mice. Moreover, arthritic clinical score was also attenuated with T0901317. Conclusion: Taken together, we show that the LXR agonist T0901317 rescues impaired atherosclerotic lesion regression in murine arthritis because of enhanced cholesterol efflux transporter expression and reduced foam cell development in atherosclerotic lesions.

Characterization of Cardiac Sympathetic Nervous System and Inflammatory Activation in HFpEF Patients.

We have shown that systemic and cardiac sympathetic activation is present in heart failure with preserved ejection fraction (HFpEF) patients. Conversely, whereas systemic inflammatory activation was also detected in HFpEF, we did not detect local myocardial release of inflammatory cytokines. Activation of the sympathetic system correlated with both hemodynamic and demographic factors that characteristically cluster together in HFpEF. Together these data suggest that there may be a role for antiadrenergic therapies in certain HFpEF patients. The study does not implicate locally derived cytokines in the myocardial biology of HFpEF, although systemic sources may contribute to the global pathophysiology of HFpEF.

A randomised preclinical trial of adrenaline use during cardiac arrest in mice.

Background: Adrenaline is routinely administered during cardiac arrest resuscitation. Using a novel murine model of cardiac arrest, this study evaluates the effects of adrenaline use on survival and end-organ injury. Methods: A total of 58 mice, including cardiac arrest (CA) and sham (SHAM) groups received intravenous potassium chloride either as a bolus (CA) or slow infusion (SHAM), inducing ECG-confirmed asystole (in CA only) for 4-minutes prior to intravenous adrenaline (+ADR;250 ul,32 ug/ml) or saline (-ADR;250 ul) and manual chest compressions (300 BPM) for 4-minutes. Mice with return of spontaneous circulation (ROSC) were assessed at 24- or 72-h timepoints. Results: Among animals that underwent CA, rates of ROSC (n = 21 (95 %) vs n = 14 (82 %), P = 0.18) and survival to the planned endpoint (n = 11 (50 %) vs n = 12 (71 %), P = 0.19) were similar when comparing those treated with (CA+ADR) and without (CA-ADR) adrenaline. However, in CA animals that initially achieved ROSC, subsequent mortality was approximately 3-fold greater with adrenaline treatment (48 % vs 14 %, P = 0.042). Among SHAM animals, adrenaline use had no impact on survival rates or other endpoints. Greater myocardial injury occurred in CA+ADR vs CA-ADR, with increased Hs-Troponin levels measured at 24- (26.0 ± 0.9 vs 9.4 ± 5.3 ng/mL, P = 0.015) and 72-h (20.9 ± 8.3 vs 5.0 ± 2.4 ng/mL, P = 0.012), associated with increased expression of pro-inflammatory and fibrotic genes within cardiac and renal tissue. Conclusion: Adrenaline did not improve ROSC or overall survival but following successful ROSC, its use resulted in 3-fold greater mortality rates. Adrenaline was also associated with increased myocardial injury, end-organ inflammation, and fibrosis. These findings underscore the need for further preclinical evaluation of alternate pharmacologic adjuncts for cardiopulmonary resuscitation that improve survival and limit end-organ injury.

A spontaneously hypertensive diet-induced atherosclerosis-prone mouse model of metabolic syndrome.

Metabolic Syndrome (MetS) is a complex and multifactorial condition often characterised by obesity, hypertension, hyperlipidaemia, insulin resistance, glucose intolerance and fasting hyperglycaemia. Collectively, MetS can increase the risk of atherosclerotic-cardiovascular disease, which is the leading cause of death worldwide. However, no animal model currently exists to study MetS in the context of atherosclerosis. In this study we developed a pre-clinical mouse model that recapitulates the spectrum of MetS features while developing atherosclerosis. When BPHx mice were placed on a western type diet for 16 weeks, all the classical characteristics of MetS were observed. Comprehensive metabolic analyses and atherosclerotic imaging revealed BPHx mice to be obese and hypertensive, with elevated total plasma cholesterol and triglyceride levels, that accelerated atherosclerosis. Altogether, we demonstrate that the BPHx mouse has all the major components of MetS, and accelerates the development of atherosclerosis.

High intraluminal pressure promotes vascular inflammation via caveolin-1.

The aetiology and progression of hypertension involves various endogenous systems, such as the renin angiotensin system, the sympathetic nervous system, and endothelial dysfunction. Recent data suggest that vascular inflammation may also play a key role in the pathogenesis of hypertension. This study sought to determine whether high intraluminal pressure results in vascular inflammation. Leukocyte adhesion was assessed in rat carotid arteries exposed to 1 h of high intraluminal pressure. The effect of intraluminal pressure on signaling mechanisms including reactive oxygen species production (ROS), arginase expression, and NFĸB translocation was monitored. 1 h exposure to high intraluminal pressure (120 mmHg) resulted in increased leukocyte adhesion and inflammatory gene expression in rat carotid arteries. High intraluminal pressure also resulted in a downstream signaling cascade of ROS production, arginase expression, and NFĸB translocation. This process was found to be angiotensin II-independent and mediated by the mechanosensor caveolae, as caveolin-1 (Cav1)-deficient endothelial cells and mice were protected from pressure-induced vascular inflammatory signaling and leukocyte adhesion. Cav1 deficiency also resulted in a reduction in pressure-induced glomerular macrophage infiltration in vivo. These findings demonstrate Cav1 is an important mechanosensor in pressure-induced vascular and renal inflammation.

Inhibition of interleukin-1ß signalling promotes atherosclerotic lesion remodelling in mice with inflammatory arthritis.

OBJECTIVES: Rheumatoid arthritis (RA), an inflammatory joint disorder, independently increases the risk of cardiovascular disease (CVD). IL-1ß contributes to both RA and CVD. We hypothesised that inhibiting IL-1 signalling with the IL-1R antagonist, anakinra, would dampen inflammation and promote resolution of atherosclerosis in arthritic mice. METHODS: Low-density lipoprotein receptor (Ldlr)-deficient mice were fed a Western-type diet for 14 weeks to develop atherosclerotic plaques. Mice were then switched to a chow diet, promoting lesion regression, and randomised to a control group or into groups where arthritis was induced by passive transfer of K/BxN arthritogenic serum. The arthritic mice were further randomised to vehicle or anakinra. RESULTS: Arthritis impaired atherosclerotic lesion regression when cholesterol was lowered. This was associated with a higher burden of plaque macrophages, likely due to monocytosis, driven by myelopoiesis in the bone marrow and spleen. Interestingly, delayed intervention with anakinra had no effect on arthritis in these mice. However, a significant improvement in atherosclerotic plaque remodelling to a more stable phenotype was observed. This was associated with fewer circulating monocytes, caused by a reduction in splenic extramedullary myelopoiesis. CONCLUSION: We show that inhibiting IL-1 signalling in arthritic mice with pre-existing atherosclerosis promotes lesion remodelling to a more stable phenotype, that is less likely to rupture and cause ischemic events such as myocardial infarction. This suggests that IL-1R antagonism may suppress CVD complications in patients with RA. Furthermore, inhibiting IL-1ß signalling in other patients with inflammatory diseases that also predispose to CVD may also benefit from anti-IL-1 therapy.

The effect of diet on hypertensive pathology: is there a link via gut microbiota-driven immunometabolism?

Over the past decade, the immune system has emerged as an important component in the aetiology of hypertension. There has been a blooming interest in the contribution of the gut microbiota, the microbes that inhabit our small and large intestine, to blood pressure (BP) regulation. The gastrointestinal tract houses the largest number of immune cells in our body, thus, it is no surprise that its microbiota plays an important functional role in the appropriate development of the immune system through a co-ordinated sequence of events leading to immune tolerance of commensal bacteria. Importantly, recent evidence supports that the gut microbiota can protect or promote the development of experimental hypertension and is likely to have a role in human hypertension. One of the major modulators of the gut microbiota is diet: diets that emphasize high intake of fermentable fibre, such as the Mediterranean diet and the Dietary Approaches to Stop Hypertension, promote expansion of protective microbes that release gut metabolites such as short-chain fatty acids, which are immune-, BP-, and cardio-protective, likely acting through G-coupled protein receptors. In contrast, diets lacking fibre or high in salt and fat, such as the Western diet, reduce prevalence of commensal microbial species and support a pathogenic and pro-inflammatory environment, including the release of the pro-atherosclerotic trimethylamine N-oxide. Here, we review the current understanding of the gut microbiota-driven immune dysfunction in both experimental and clinical hypertension, and how these changes may be addressed through dietary interventions.

Glycolysis Is Required for LPS-Induced Activation and Adhesion of Human CD14+CD16- Monocytes.

Monocytes in humans consist of 3 subsets; CD14+CD16- (classical), CD14+CD16+ (intermediate) and CD14dimCD16+ (non-classical), which exhibit distinct and heterogeneous responses to activation. During acute inflammation CD14+CD16- monocytes are significantly elevated and migrate to the sites of injury via the adhesion cascade. The field of immunometabolism has begun to elucidate the importance of the engagement of specific metabolic pathways in immune cell function. Yet, little is known about monocyte metabolism and the role of metabolism in mediating monocyte activation and adherence to vessels. Accordingly, we aimed to determine whether manipulating the metabolism of CD14+CD16- monocytes alters their ability to become activated and adhere. We discovered that LPS stimulation increased the rate of glycolysis in human CD14+CD16- monocytes. Inhibition of glycolysis with 2-deoxy-D-glucose blunted LPS-induced activation and adhesion of monocytes. Mechanistically, we found that increased glycolysis was regulated by mTOR-induced glucose transporter (GLUT)-1. Furthermore, enhanced glycolysis increased accumulation of reactive oxygen species (ROS) and activation of p38 MAPK, which lead to activation and adhesion of monocytes. These findings reveal that glycolytic metabolism is critical for the activation of CD14+CD16- monocytes and contributes to our understanding of the interplay between metabolic substrate preference and immune cell function.

Serum Amyloid A Stimulates Vascular and Renal Dysfunction in Apolipoprotein E-Deficient Mice Fed a Normal Chow Diet.

Elevated serum amyloid A (SAA) levels may promote endothelial dysfunction, which is linked to cardiovascular and renal pathologies. We investigated the effect of SAA on vascular and renal function in apolipoprotein E-deficient (ApoE-/-) mice. Male ApoE-/- mice received vehicle (control), low-level lipopolysaccharide (LPS), or recombinant human SAA by i.p. injection every third day for 2 weeks. Heart, aorta and kidney were harvested between 3 days and 18 weeks after treatment. SAA administration increased vascular cell adhesion molecule (VCAM)-1 expression and circulating monocyte chemotactic protein (MCP)-1 and decreased aortic cyclic guanosine monophosphate (cGMP), consistent with SAA inhibiting nitric oxide bioactivity. In addition, binding of labeled leukocytes to excised aorta increased as monitored using an ex vivo leukocyte adhesion assay. Renal injury was evident 4 weeks after commencement of SAA treatment, manifesting as increased plasma urea, urinary protein, oxidized lipids, urinary kidney injury molecule (KIM)-1 and multiple cytokines and chemokines in kidney tissue, relative to controls. Phosphorylation of nuclear-factor-kappa-beta (NFκB-p-P65), tissue factor (TF), and macrophage recruitment increased in kidneys from ApoE-/- mice 4 weeks after SAA treatment, confirming that SAA elicited a pro-inflammatory and pro-thrombotic phenotype. These data indicate that SAA impairs endothelial and renal function in ApoE-/- mice in the absence of a high-fat diet.

Is There a Potential Therapeutic Role for Caveolin-1 in Fibrosis?

Fibrosis is a process of dysfunctional wound repair, described by a failure of tissue regeneration and excessive deposition of extracellular matrix, resulting in tissue scarring and subsequent organ deterioration. There are a broad range of stimuli that may trigger, and exacerbate the process of fibrosis, which can contribute to the growing rates of morbidity and mortality. Whilst the process of fibrosis is widely described and understood, there are no current standard treatments that can reduce or reverse the process effectively, likely due to the continuing knowledge gaps surrounding the cellular mechanisms involved. Several cellular targets have been implicated in the regulation of the fibrotic process including membrane domains, ion channels and more recently mechanosensors, specifically caveolae, particularly since these latter contain various signaling components, such as members of the TGFß and MAPK/ERK signaling pathways, all of which are key players in the process of fibrosis. This review explores the anti-fibrotic influences of the caveola, and in particular the key underpinning protein, caveolin-1, and its potential as a novel therapeutic target.

Caveolae: A Role in Endothelial Inflammation and Mechanotransduction?

Vascular inflammation and disease progression, such as atherosclerosis, are in part a consequence of haemodynamic forces generated by changes in blood flow. The haemodynamic forces, such as shear stress or stretch, interact with vascular endothelial cells, which transduce the mechanical stimuli into biochemical signals via mechanosensors, which can induce an upregulation in pathways involved in inflammatory signaling. However, it is unclear how these mechanosensors respond to shear stress and most significantly what cellular mechanisms are involved in sensing the haemodynamic stimuli. This review explores the transition from shear forces, stretch and pressure to endothelial inflammation and the process of mechanotransduction, specifically highlighting evidence to suggest that caveolae play as a role as mechanosensors.