Irbesartan attenuates production of high-mobility group box 1 in response to lipopolysaccharide via downregulation of interferon-β production

Irbesartan has a curative effect on lipopolysaccharide-induced cardiotoxicity by antioxidant and antiapoptotic pathways

INTRODUCTION AND OBJECTIVE

Lipopolysaccharide (LPS) has been associated with myocardial inflammation, oxidative stress, apoptosis, and cardiac dysfunction, as well as death by causing sepsis. In this study, we investigated the effect of irbesartan (IRB), an angiotensin receptor antagonist, on cardiotoxicity caused by LPS.

METHODS

The experiment involved 24 Wistar albino rats divided into three groups of eight: control, LPS (5 mg/kg), and LPS (5 mg/kg)+IRB (3 mg/kg). Parameters including total oxidative status, total antioxidant status, oxidative stress index, and ischemia-modified albumin were measured to assess oxidative stress in heart tissues and serum. Serum CK, CK-MB, and LDH levels were measured spectrophotometrically. RT-qPCR was used to detect the mRNA expression levels of Bcl-2, BAX, p53, caspase-3, and sirtuin 1. Tissues taken from the heart and aorta were examined by immunohistochemistry and histopathology.

RESULTS

While there was an increase in the parameters indicating heart damage, oxidative stress, and apoptosis in the group given LPS, there was an improvement in all parameters and heart damage in the group treated with IRB.

CONCLUSION

As a result of our study, we determined that IRB has an ameliorating effect on myocardial damage caused by oxidative stress and apoptosis developed by the LPS-induced sepsis model.

Irbesartan reprofiling for the amelioration of ethanol-induced gastric mucosal injury in rats: Role of inflammation, apoptosis, and autophagy

BACKGROUND

Pronounced anti-inflammatory and anti-apoptotic features have been characterized for the angiotensin receptor blocker irbesartan. Yet, its effect on ethanol-induced gastropathy has not been studied. The present work explored the potential modulation of inflammatory, apoptotic, and autophagic events by irbesartan for the attenuation of ethanol-evoked gastric mucosal injury.

METHODOLOGY

Wistar rats were divided into control, control + irbesartan, ethanol, ethanol + irbesartan, and ethanol + omeprazole groups. Macroscopic examination, histopathology, immunohistochemistry, and biochemical assays were applied to examine the gastric tissues.

KEY FINDINGS

Irbesartan administration (50 mg/kg; by gavage) in ethanol-evoked gastropathy improved the gastric pathological manifestations (area of gastric lesion and ulcer index scores), histopathological changes, and microscopic damage scores. These beneficial effects were interceded by suppression of the HMGB1-associated inflammatory events and the linked downregulation of the nuclear NF-κBp65 protein expression. In the meantime, curtailing of the NLRP3 inflammasome by irbesartan was observed with consequent decline of the pro-inflammatory cytokine IL-1β. In tandem, upregulation of the antioxidant Nrf2 and the cytoprotective PPAR-γ were seen. Together, suppression of the pro-inflammatory cues and pro-oxidant signals attenuated the pro-apoptotic events as evidenced by Bcl-2 upregulation, Bax downregulation, and caspase 3 dampened activity. Regarding gastric autophagy signals, irbesartan diminished SQSTM-1/p62 accumulation and upregulated Beclin 1. This was associated with gastric AMPK/mTOR pathway activation evidenced by increased AMPK (Ser487) phosphorylation and lowered mTOR (Ser2448) phosphorylation.

CONCLUSION

Suppression of the inflammatory and apoptotic signals and upregulation of the pro-autophagy events may advocate the promising gastroprotective actions of irbesartan against ethanol-induced gastric injury.

Immunomodulatory Activity of the Most Commonly Used Antihypertensive Drugs-Angiotensin Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers

This review article is focused on antihypertensive drugs, namely angiotensin converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB), and their immunomodulatory properties reported in hypertensive patients as well as in experimental settings involving studies on animal models and cell lines. The immune regulatory action of ACEI and ARB is mainly connected with the inhibition of proinflammatory cytokine secretion, diminished expression of adhesion molecules, and normalization of CRP concentration in the blood plasma. The topic has significant importance in future medical practice in the therapy of patients with comorbidities with underlying chronic inflammatory responses. Thus, this additional effect of immune regulatory action of ACEI and ARB may also benefit the treatment of patients with metabolic syndrome, allergies, or autoimmune disorders.

Angiotensin II Increases HMGB1 Expression in the Myocardium Through AT1 and AT2 Receptors When Under Pressure Overload

High-mobility group box 1 (HMGB1) is increased in the myocardium under pressure overload (PO) and is involved in PO-induced cardiac remodeling. The mechanisms of the upregulation of cardiac HMGB1 expression have not been fully elucidated. In the present study, a mouse transverse aortic constriction (TAC) model was used, and an angiotensin II (Ang II) type 1 (AT1) receptor inhibitor (losartan) or Ang II type 2 (AT2) receptor inhibitor (PD123319) was administrated to mice for 14 days. Cardiac myocytes were cultured and treated with Ang II for 5 minutes to 48 hours conditionally with the blockage of the AT1 or AT2 receptor. TAC-induced cardiac hypertrophy was observed at 14 days after the operation, which was partially reversed by losartan, but not by PD123319. Similarly, the upregulated HMGB1 expression levels observed in both the serum and myocardium induced by TAC were reduced by losartan. Elevated cardiac HMGB1 protein levels, but not mRNA or serum levels, were significantly decreased by PD123319. Furthermore, HMGB1 expression levels in culture media and cardiac myocytes were increased following Ang II treatment in vitro, positively associated with the duration of treatment. Similarly, Ang II-induced upregulation of HMGB1 in vitro was inhibited by both losartan and PD123319. These results suggest that upregulation of HMGB1 in serum and myocardium under PO, which are partially derived from cardiac myocytes, may be induced by Ang II via the AT1 and AT2 receptors. Additionally, amelioration of PO-induced cardiac hypertrophy following losartan treatment may be associated with the reduction of HMGB1 expression through the AT1 receptor.