Renal Artery Coil Embolization as an Endovascular Approach for Establishing a Rabbit Model of Chronic Kidney Disease

PURPOSE

To investigate the safety and feasibility of renal artery coil embolization for establishing chronic kidney disease (CKD) in rabbits.

MATERIALS AND METHODS

Ten male adult New Zealand rabbits underwent renal artery coil embolization. Initially, the main renal artery on 1 side was completely embolized, followed by embolization of approximately two-thirds of the primary branches of the contralateral renal artery 1 week later. Four rabbits were randomly chosen for sacrifice at 4 weeks after embolization, whereas the remaining 6 were sacrificed at 8 weeks after embolization. The assessment encompassed the animals' general condition, angiography, biochemical parameters, inflammatory markers, and histopathological examination of the kidneys and hearts.

RESULTS

Four weeks after embolization, serum creatinine level showed a substantial increase (2.4 mg/dL [SD ± 0.6]; P = .009 vs baseline), with a subsequent 4.12-fold elevation at 8 weeks after embolization (4.9 mg/dL [SD ± 1.4]; P < .001 vs baseline). Additionally, considerable increases in serum blood urea nitrogen, calcium, and potassium ions were observed at 8 weeks after embolization (58.3 mg/dL [SD ± 19.0]; P < .001 vs baseline; 23.1 mg/dL [SD ± 4.4]; P < .001 vs baseline; and 6.3 mEq/L [SD ± 0.7]; P < .001 vs baseline, respectively). The completely embolized kidney exhibited notable atrophy, severe fibrosis, and cortical calcification, whereas the contralateral partially embolized kidney displayed compensatory hypertrophy, along with glomerulosclerosis, tubular dilation, tubular casts, and interstitial fibrosis.

CONCLUSIONS

Renal artery coil embolization proved to be effective and safe for establishing a CKD model in rabbits.

Angelica acutiloba Exerts Antihypertensive Effect and Improves Insulin Resistance in Spontaneously Hypertensive Rats Fed with a High-Fat Diet

INTRODUCTION

Angelica acutiloba is one of the crude drugs used in Chinese herbal medicine, and its intake is expected to improve metabolic syndrome-associated disorders. Here, we examined the effects of A. acutiloba extract (AAE) on hypertension and insulin resistance induced by the treatment of high-fat diet (HFD) to spontaneously hypertensive rats (SHRs). Then, we investigated the mechanisms associated with the effects of AAE.

METHODS

AAE was administered to HFD-fed SHRs. Systolic blood pressure (SBP), sympathetic nerve activity, hypothalamic angiotensin-converting enzyme (ACE) activity, blood glucose level, plasma insulin concentration, visceral fat mass, and gene expression of tumor necrosis factor-alpha (TNF-α) in the visceral fat were evaluated.

RESULTS

AAE reduced the increases in SBP and hypothalamic ACE activity observed in the HFD-fed SHRs, whereas the suppressive effect on sympathetic nerve activity was slight. Environmental stress-induced pressure and sympathetic overactivity were suppressed by the treatment of AAE. It also decreased the increase in the blood glucose level, plasma insulin concentration, homeostasis model assessment for the insulin resistance, and TNF-α gene expression in the visceral fat, but not the increase in the visceral fat mass.

CONCLUSION

AAE has an antihypertensive effect, suppresses stress-induced hypertension, and improves insulin resistance in HFD-fed SHRs. The suppression of brain ACE activity, sympathetic nerve activity, and inflammation are partly involved in the effects of AAE.

Activation of AMPK by Telmisartan Decreases Basal and PDGF-stimulated VSMC Proliferation via Inhibiting the mTOR/p70S6K Signaling Axis

BACKGROUND

Telmisartan, an angiotensin II type 1 receptor blocker (ARB), is widely used to treat hypertension by blocking the renin-angiotensin-aldosterone system. Although abnormal proliferation of vascular smooth muscle cells (VSMCs) is a well-established contributor to the development of various vascular diseases, such as atherosclerosis, the effect of telmisartan on VSMC proliferation and its mechanism of action have not been fully revealed. Herein, we investigated the molecular mechanism whereby telmisartan inhibits rat VSMC proliferation.

METHODS

We measured VSMC proliferation by MTT assay, and performed inhibitor studies and western blot analyses using basal and platelet-derived growth factor (PDGF)-stimulated rat VSMCs. To elucidate the role of AMP-activated protein kinase (AMPK), we introduced dominant-negative (dn)-AMPKα1 gene into VSMCs.

RESULTS

Telmisartan decreased VSMC proliferation, which was accompanied by decreased phosphorylations of mammalian target of rapamycin (mTOR) at Ser2448 (p-mTOR-Ser²⁴⁴⁸) and p70 S6 kinase (p70S6K) at Thr389 (p-p70S6K-Thr³⁸⁹) in dose- and time-dependent manners. Telmisartan dose- and time-dependently increased phosphorylation of AMPK at Thr172 (p-AMPK-Thr¹⁷²). Co-treatment with compound C, a specific AMPK inhibitor, or ectopic expression of the dn-AMPKα1 gene, significantly reversed telmisartan-inhibited VSMC proliferation, p-mTOR-Ser²⁴⁴⁸ and p-p70S6K-Thr³⁸⁹ levels. Among the ARBs tested (including losartan and fimasartan), only telmisartan increased p-AMPK-Thr¹⁷² and decreased p-mTOR-Ser²⁴⁴⁸, p-p70S6K-Thr³⁸⁹, and VSMC proliferation. Furthermore, GW9662, a specific and irreversible peroxisome proliferator-activated receptor γ (PPARγ) antagonist, did not affect any of the telmisartan-induced changes. Finally, telmisartan also exhibited inhibitory effects on VSMC proliferation by increasing p-AMPK-Thr¹⁷² and decreasing p-mTOR-Ser²⁴⁴⁸ and p-p70S6K-Thr³⁸⁹ in a PDGF-induced in vitro atherosclerosis model.

CONCLUSION

These results demonstrated that telmisartan-activated AMPK inhibited basal and PDGF-stimulated VSMC proliferation, at least in part, by downregulating the mTOR/p70S6K signaling axis in a PPARγ-independent manner. These observations suggest that telmisartan could be used to treat arterial narrowing diseases such as atherosclerosis and restenosis.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Clinical Significance of Endothelial Dysfunction in Essential Hypertension

The endothelium is recognized as a major determinant of vascular physiology and pathophysiology. Over the last few decades, a plethora of studies have implicated endothelial dysfunction in the progression of atherosclerosis and the subclinical target organ damage observed in essential hypertension. However, the clinical significance of diagnosing endothelial dysfunction in patients with essential hypertension remains under investigation. Although a number of vascular and non-vascular markers of endothelial dysfunction have been proposed, there is an ongoing quest for a marker in the clinical setting that is optimal, inexpensive, and reproducible. In addition, endothelial dysfunction emerges as a promising therapeutic target of agents that are readily available in clinical practice. In this context, a better understanding of its role in essential hypertension becomes of great importance. Here, we aim to investigate the clinical significance of endothelial dysfunction in essential hypertension by accumulating novel data on (a) early diagnosis using robust markers with prognostic value in cardiovascular risk prediction, (b) the association of endothelial dysfunction with subclinical vascular organ damage, and (c) potential therapeutic targets.

Telmisartan enhances mitochondrial activity and alters cellular functions in human coronary artery endothelial cells via AMP-activated protein kinase pathway

OBJECTIVE

Mitochondrial dysfunction plays an important role in cellular senescence and impaired function of vascular endothelium, resulted in cardiovascular diseases. Telmisartan is a unique angiotensin II type I receptor blocker that has been shown to prevent cardiovascular events in high risk patients. AMP-activated protein kinase (AMPK) plays a critical role in mitochondrial biogenesis and endothelial function. This study assessed whether telmisartan enhances mitochondrial function and alters cellular functions via AMPK in human coronary artery endothelial cells (HCAECs).

METHODS AND RESULTS

In cultured HCAECs, telmisartan significantly enhanced mitochondrial activity assessed by mitochondrial reductase activity and intracellular ATP production and increased the expression of mitochondria related genes. Telmisartan prevented cellular senescence and exhibited the anti-apoptotic and pro-angiogenic properties. The expression of genes related anti-oxidant and pro-angiogenic properties were increased by telmisartan. Telmisartan increased endothelial NO synthase and AMPK phosphorylation. Peroxisome proliferator-activated receptor gamma signaling was not involved in telmisartan-induced improvement of mitochondrial function. All of these effects were abolished by inhibition of AMPK.

CONCLUSIONS

Telmisartan enhanced mitochondrial activity and exhibited anti-senescence effects and improving endothelial function through AMPK in HCAECs. Telmisartan could provide beneficial effects on vascular diseases via enhancement of mitochondrial activity and modulating endothelial function through AMPK activation.