Ameliorative effect of AT2R and ACE2 activation on ischemic renal injury associated cardiac and hepatic dysfunction

https://doi.org/10.1016/j.etap.2020.103501Get rights and content

Highlights

  • Diabetic rats are more prone towards cardio-hepatic impairments under IRI.

  • IRI elevated oxidative stress, inflammation & suppressed depressor arm of RAS.

  • Treatment with C21 & Dize significantly attenuated oxidative stress & inflammation.

  • Combination of C21 & Dize upregulated the cardio-hepatic depressor arm of RAS.

  • C21 & Dize combination; novel therapeutic approach to curb cardio-hepatic sequalae.

Abstract

This study explored the role of the depressor arm of renin-angiotensin system (RAS) on ischemic renal injury (IRI)-associated cardio-hepatic sequalae under non-diabetic (ND) and diabetes mellitus (DM) conditions. Firstly, rats were injected with Streptozotocin (55 mg/kg i.p.) to develop DM. ND and DM rats underwent Bilateral IRI followed by 24 h of reperfusion. Further, ND and DM rats were subjected to AT2R agonist-Compound 21 (C21) (0.3 mg/kg/day, i.p.) or ACE2 activator- Diminazene Aceturate (Dize), (5 mg/kg/day, p.o.) per se or its combination therapy. As results, IRI caused cardio-hepatic injuries via altered oxidant/anti-oxidant levels, elevated inflammatory events, and altered protein expressions of ACE, ACE2, Ang II, Ang-(1–7) and urinary AGT. However, concomitant therapy of AT2R agonist and ACE2 activator exerts a protective effect in IRI-associated cardio-hepatic dysfunction as evidenced by inhibited oxidative stress, downregulated inflammation, and enhanced cardio-hepatic depressor arm of RAS under ND and DM conditions.

Introduction

Acute kidney injury (AKI) is one of the major challenging medical conditions for which there is no defined therapy so far (Vanmassenhove et al., 2017). Under clinical settings, the association of co-morbidities, such as diabetes made patients more vulnerable to AKI (Monseu et al., 2015). Among various factors, ischemic renal injury (IRI) remains the most common cause of AKI. Moreover, AKI-induced multiorgan dysfunction is of serious concern because it results in a higher mortality rate (Lee et al., 2018). Due to the organ crosstalk, the renal injury may cause damage to distant organs such as liver, heart, brain, lungs, intestines and bone marrow; however, the precise mechanism behind is still elusive. Nevertheless, possible pathways proposed by the scientists such as vascular inflammation, metabolic acidosis, electrolyte imbalances triggered life-threatening arrhythmias, reactive oxygen species (ROS), upregulation of systemic cytokines, neurohumoral factors, and proapoptotic pathways (Bucsics and Krones, 2017; Lee et al., 2018; Panicoa et al., 2019). Besides these known characteristic mechanisms, there is another crucial factor with immediate impact on distant organs, i.e., the renin-angiotensin system (RAS) (Bucsics and Krones, 2017; Panicoa et al., 2019).

Recently, we have thoroughly reviewed the role of RAS controlling several pathological signalling that contributes to AKI (Sharma et al., 2019a). In clinical settings, treatment with pressor arm modulators, i.e. angiotensin converting enzyme inhibitor (ACEi) and angiotensin II type 2 receptor blockers (ARBs) claimed to worsens the patients’ condition via deteriorating glomerular filtration rate (Mansfield et al., 2016). Hence, we established the role of depressor arm of RAS in IRI under normal- and hyperglycaemia condition (Sharma et al., 2019b). Our report explained that diabetic unilateral-ischemic rats presented up- and downregulation of pressor RAS and depressor RAS, respectively, resulted in a rapid upsurge of free radical generation, inflammation, apoptotic markers along with severe histological alterations in the proximal tubules. Further, treatment with depressor arm modulators; Compound 21 (C21) and Diminazene aceturate (Dize), the depressor arm components get over-expressed which suppressed the pathological signalling in IRI and protected the proximal tubular morphological alterations (Sharma et al., 2019b). Remarkably, the clinical relevance proposed that all the organs have their own local RAS, which remains compartmentalised from the circulation (Campbell, 2014). Following a similar approach, recent reports have demonstrated the activation of local RAS in distant organs; heart and liver (Taskin and Guven, 2017; Panicoa et al., 2019). Nevertheless, the role of the depressor arm of RAS in IRI-induced cardio-hepatic dysfunction remains elusive. Hence, in the current study, we utilised a bilateral renal IRI model of diabetic and nondiabetic rats to test the hypothesis that IRI could alter the cardio-hepatic levels of AT2R and ACE2 which could arbitrate inflammation and oxidative stress in the same.

Section snippets

Chemicals

Glucose, plasma creatinine (PCr), blood urea nitrogen (BUN), Creatine kinase-MB (CK-MB), Lactate dehydrogenase (LDH), Aspartate aminotransferase (AST), alanine transaminase (ALT) kits obtained from Accurex (Mumbai, India). Chemicals like Streptozotocin and Diminazene aceturate (Dize) obtained from Sigma (St. Louis, MO, USA). ELISA kits for Kidney injury molecule-1 (Kim-1), ACE, ACE2, Ang-(1–7), Ang II, AGT and Myeloperoxidase (MPO) purchased from Elabsciences (China). Primary antibody of tumour

Effect of AT2R and ACE2 activation on kidney functional parameters

Under the hyperglycemic condition, DM rats showed increased (P < 0.05) plasma glucose levels compared to ND rats (Table 1). However, either IRI or AT2R/ACE2 activation did not decreased the level of plasma glucose (Table 1). In ND and DM rats, IRI had significantly elevated (P < 0.05) the BUN and PCr levels, where DM-IRI group showed significant elevation in BUN and PCr levels as compared to ND-IRI group. Urinary Kim-1, a type 1 transmembrane protein, served as the biomarker of AKI was found to

Discussion

Mounting shreds of evidence demonstrated that several cellular and molecular mechanisms play specific roles in the IRI, instead of the usual possible treatments, no effective therapy has been appraised, so far (Doyle and Forni, 2016). Clinical reports have demonstrated that mortality rate soared from 45 % to 60 % when AKI was associated with distant organ insufficiency and co-morbidities (such as diabetes) (Lee et al., 2018). As compared to non-diabetics, diabetic patients endure a higher risk

Conclusion

In conclusion, to the best of our knowledge, this is the first report that upregulation of depressor arm of RAS exerted significant protective effects on the heart and liver during IRI in ND and DM conditions. This potential mechanism of combination therapy of AT2R and ACE2 activation is associated with normalised biochemical markers, anti-oxidative and anti-inflammatory capability. These results support the proposition that depressor arm modulators hold potential for novel therapeutic

Author contributions

N.S. perceived the idea and A.B.G. framed and supervised the experiments. N.S. performed the experiments and completed the manuscript writing. Both authors read and approved the manuscript.

Funding

This research was funded by the Science & Engineering Research Board -Department of Science & Technology (SERB-DST), Govt. of India [SERB/ECR/2017/000317].

CRediT authorship contribution statement

Nisha Sharma: Conceptulization, Data curation, Methodology, Formal analysis, Writing - original draft. Anil Bhanudas Gaikwad: Supervision, Validation, Writing - review & editing.

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgements

N.S. sincerely grateful to the Indian Council of Medical Research (ICMR) for providing senior research fellowship [45/54/2019/PHA/BMS]. The authors also acknowledge Anders Ljunggren, Vicore Pharma, Sweden, for his valuable suggestions and for offering the drug sample, Compound 21.

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