HDAC inhibition attenuates inflammatory, hypertrophic, and hypertensive responses in spontaneously hypertensive rats

Angiotensin II-induced hypertension is modulated by nuclear factor-κBin the paraventricular nucleus

Hypertension is considered a low-grade inflammatory condition, and understanding the role of transcription factors in guiding this response is pertinent. A prominent transcription factor that governs inflammatory responses and has become a focal point in hypertensive research is nuclear factor-κB (NFκB). Within the hypothalamic paraventricular nucleus (PVN), a known brain cardioregulatory center, NFκB becomes potentially even more important in ultimately coordinating the systemic hypertensive response. To definitively demonstrate the role of NFκB in the neurogenic hypertensive response, we hypothesized that PVN NFκB blockade would attenuate angiotensin II-induced hypertension. Twelve-week-old male Sprague-Dawley rats were implanted with radiotelemetry probes for blood pressure measurement and allowed a 7-day recovery. After baseline blood pressure recordings, rats were administered either continuous NFκB decoy oligodeoxynucleotide infusion or microinjection of a serine mutated adenoviral inhibitory-κB vector, or their respective controls, bilaterally into the PVN to inhibit NFκB at two levels of its activation pathway. Simultaneously, rats were implanted subcutaneously with an angiotensin II or saline-filled 14-day osmotic minipump. After the 2-week treatments, rats were euthanized and brain tissues collected for PVN analysis. Bilaterally inhibited NFκB rats had a decrease in blood pressure, NFκB p65 subunit activity, proinflammatory cytokines, and reactive oxygen species, including the angiotensin II type 1 receptor, angiotensin-converting enzyme, tumor necrosis factor, and superoxide in angiotensin II-treated rats. Moreover, after NFκB blockade, key protective antihypertensive renin-angiotensin system components were upregulated. This demonstrates the important role that transcription factor NFκB plays within the PVN in modulating and perpetuating the hypertensive response via renin-angiotensin system modulation.

A blueberry-enriched diet attenuates nephropathy in a rat model of hypertension via reduction in oxidative stress

OBJECTIVE AND BACKGROUND

To assess renoprotective effects of a blueberry-enriched diet in a rat model of hypertension. Oxidative stress (OS) appears to be involved in the development of hypertension and related renal injury. Pharmacological antioxidants can attenuate hypertension and hypertension-induced renal injury; however, attention has shifted recently to the therapeutic potential of natural products as antioxidants. Blueberries (BB) have among the highest antioxidant capacities of fruits and vegetables.

METHODS AND RESULTS

Male spontaneously hypertensive rats received a BB-enriched diet (2% w/w) or an isocaloric control diet for 6 or 12 weeks or 2 days. Compared to controls, rats fed BB-enriched diet for 6 or 12 weeks exhibited lower blood pressure, improved glomerular filtration rate, and decreased renovascular resistance. As measured by electron paramagnetic resonance spectroscopy, significant decreases in total reactive oxygen species (ROS), peroxynitrite, and superoxide production rates were observed in kidney tissues in rats on long-term dietary treatment, consistent with reduced pathology and improved function. Additionally, measures of antioxidant status improved; specifically, renal glutathione and catalase activities increased markedly. Contrasted to these observations indicating reduced OS in the BB group after long-term feeding, similar measurements made in rats fed the same diet for only 2 days yielded evidence of increased OS; specifically, significant increases in total ROS, peroxynitrite, and superoxide production rates in all tissues (kidney, brain, and liver) assayed in BB-fed rats. These results were evidence of "hormesis" during brief exposure, which dissipated with time as indicated by enhanced levels of catalase in heart and liver of BB group.

CONCLUSION

Long-term feeding of BB-enriched diet lowered blood pressure, preserved renal hemodynamics, and improved redox status in kidneys of hypertensive rats and concomitantly demonstrated the potential to delay or attenuate development of hypertension-induced renal injury, and these effects appear to be mediated by a short-term hormetic response.

Antihypertensive effects of peroxisome proliferator-activated receptor-β activation in spontaneously hypertensive rats

Activation of nuclear hormone receptor peroxisome proliferator-activated receptor β/δ (PPARβ) has been shown to improve insulin resistance and plasma high-density lipoprotein levels, but nothing is known about its effects in genetic hypertension. We studied whether the PPARβ agonist GW0742 might exert antihypertensive effects in spontaneously hypertensive rats (SHRs). The rats were divided into 4 groups, Wistar Kyoto rat-control, Wistar Kyoto rat-treated (GW0742, 5 mg · kg(-1) · day(-1) by oral gavage), SHR-control, and SHR-treated, and followed for 5 weeks. GW0742 induced a progressive reduction in systolic arterial blood pressure and heart rate in SHRs and reduced the mesenteric arterial remodeling, the increased aortic vasoconstriction to angiotensin II, and the endothelial dysfunction characteristic of SHRs. These effects were accompanied by a significant increase in endothelial NO synthase activity attributed to upregulated endothelial NO synthase and downregulated caveolin 1 protein expression. Moreover, GW0742 inhibited vascular superoxide production, downregulated p22(phox) and p47(phox) proteins, decreased both basal and angiotensin II-stimulated NADPH oxidase activity, inhibited extracellular-regulated kinase 1/2 activation, and reduced the expression of the proinflammatory and proatherogenic genes, interleukin 1β, interleukin 6, or intercellular adhesion molecule 1. None of these effects were observed in Wistar Kyoto rats. PPARβ activation, both in vitro and in vivo, increased the expression of the regulators of G protein-coupled signaling proteins RGS4 and RGS5, which negatively modulated the vascular actions of angiotensin II. PPARβ activation exerted antihypertensive effects, restored the vascular structure and function, and reduced the oxidative, proinflammatory, and proatherogenic status of SHRs. We propose PPARβ as a new therapeutic target in hypertension.

Telmisartan provides better renal protection than valsartan in a rat model of metabolic syndrome

BACKGROUND

Angiotensin receptor blockers (ARB), telmisartan, and valsartan were compared for renal protection in spontaneously hypertensive rats (SHR) fed high fat diet. We hypothesized that in cardiometabolic syndrome, telmisartan an ARB with peroxisome proliferators activated receptor-γ (PPAR-γ) activity will offer better renal protection.

METHODS

SHR were fed either normal (SHR-NF, 7% fat) or high fat (SHR-HF, 36% fat) diet and treated with an ARB for 10 weeks.

RESULTS

Blood pressure was similar between SHR-NF (190 ± 3 mm Hg) and SHR-HF (192 ± 4 mm Hg) at the end of the 10 week period. Telmisartan and valsartan decreased blood pressure to similar extents in SHR-NF and SHR-HF groups. Body weight was significantly higher in SHR-HF (368 ± 5 g) compared to SHR-NF (328 ± 7 g). Telmisartan but not valsartan significantly reduced the body weight gain in SHR-HF. Telmisartan was also more effective than valsartan in improving glycemic and lipid status in SHR-HF. Monocyte chemoattractant protein-1 (MCP-1), an inflammatory marker, was higher in SHR-HF (24 ± 2 ng/d) compared to SHR-NF (14 ± 5 ng/d). Telmisartan reduced MCP-1 excretion in both SHR-HF and SHR-NF to a greater extent than valsartan. An indicator of renal injury, urinary albumin excretion increased to 85 ± 8 mg/d in SHR-HF compared to 54 ± 9 mg/d in SHR-NF. Telmisartan (23 ± 5 mg/d) was more effective than valsartan (45 ± 3 mg/d) in lowering urinary albumin excretion in SHR-HF. Moreover, telmisartan reduced glomerular damage to a greater extent than valsartan in the SHR-HF.

CONCLUSIONS

Collectively, our data demonstrate that telmisartan was more effective than valsartan in reducing body weight gain, renal inflammation, and renal injury in a rat model of cardiometabolic syndrome.

Cardiac HDAC6 catalytic activity is induced in response to chronic hypertension

Small molecule histone deacetylase (HDAC) inhibitors block adverse cardiac remodeling in animal models of heart failure. The efficacious compounds target class I, class IIb and, to a lesser extent, class IIa HDACs. It is hypothesized that a selective inhibitor of a specific HDAC class (or an isoform within that class) will provide a favorable therapeutic window for the treatment of heart failure, although the optimal selectivity profile for such a compound remains unknown. Genetic studies have suggested that class I HDACs promote pathological cardiac remodeling, while class IIa HDACs are protective. In contrast, nothing is known about the function or regulation of class IIb HDACs in the heart. We developed assays to quantify catalytic activity of distinct HDAC classes in left and right ventricular cardiac tissue from animal models of hypertensive heart disease. Class I and IIa HDAC activity was elevated in some but not all diseased tissues. In contrast, catalytic activity of the class IIb HDAC, HDAC6, was consistently increased in stressed myocardium, but not in a model of physiologic hypertrophy. HDAC6 catalytic activity was also induced by diverse extracellular stimuli in cultured cardiac myocytes and fibroblasts. These findings suggest an unforeseen role for HDAC6 in the heart, and highlight the need for pre-clinical evaluation of HDAC6-selective inhibitors to determine whether this HDAC isoform is pathological or protective in the setting of cardiovascular disease.

Targeting inflammation in heart failure with histone deacetylase inhibitors

Cardiovascular insults such as myocardial infarction and chronic hypertension can trigger the heart to undergo a remodeling process characterized by myocyte hypertrophy, myocyte death and fibrosis, often resulting in impaired cardiac function and heart failure. Pathological cardiac remodeling is associated with inflammation, and therapeutic approaches targeting inflammatory cascades have shown promise in patients with heart failure. Small molecule histone deacetylase (HDAC) inhibitors block adverse cardiac remodeling in animal models, suggesting unforeseen potential for this class of compounds for the treatment of heart failure. In addition to their beneficial effects on myocardial cells, HDAC inhibitors have potent antiinflammatory actions. This review highlights the roles of HDACs in the heart and the potential for using HDAC inhibitors as broad-based immunomodulators for the treatment of human heart failure.

Rationale for HDAC inhibitor therapy in autoimmunity and transplantation

While there are currently more than 70 ongoing clinical trials of inhibitors of so-called classical HDACs (HDACi) as anticancer therapies, given their potency as antiproliferative and angiostatic agents, HDACi also have considerable therapeutic potential as anti-inflammatory and immunosuppressive drugs. The utility of HDACi as anti-inflammatory agents is dependent upon their proving safe and effective in experimental models. Current pan-HDACi compounds are not well suited to this role, given the broad distribution of target HDACs and their complex and multifaceted mechanisms of action. In contrast, the development of isoform-selective HDACi may provide important new tools for therapy in autoimmunity and transplantation. This chapter discusses which HDACs are worthwhile targets in inflammation and progress toward their therapeutic inhibition, including the use of HDAC subclass and isoform-selective HDACi to promote the functions of Foxp3+ T regulatory cells.

Isoform-selective HDAC inhibitors: closing in on translational medicine for the heart

Small molecule histone deacetylase (HDAC) inhibitors block adverse cardiac remodeling in animal models, suggesting unforeseen potential for this class of compounds for the treatment of heart failure. However, since broad-spectrum, "pan" HDAC inhibition is associated with toxicities such as thrombocytopenia, nausea and fatigue, many in the field remain skeptical of the prospects of translating these findings to the heart failure clinic. Robust medicinal chemistry efforts in industry and academics have led to the discovery of small molecules that selectively inhibit one or a small subset of the 18 human HDACs, and many of these compounds appear to exhibit improved safety profiles. This work has set the stage for identification of the HDAC isoform(s) that promote pathological cardiac remodeling, and advancement of safer HDAC inhibitors into clinical trials for heart failure. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".