Intermedin Alleviates Renal Ischemia-Reperfusion Injury and Enhances Neovascularization in Wistar Rats

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.

Multi-biological functions of intermedin in diseases

Intermedin (IMD) is a member of the calcitonin gene-related peptide (CGRP)/calcitonin (CT) superfamily, and it is expressed extensively throughout the body. The typical receptors for IMD are complexes composed of calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein (RAMP), which leads to a biased activation towards Gαs. As a diagnostic and prognostic biomarker, IMD regulates the initiation and metastasis of multiple tumors. Additionally, IMD functions as a proangiogenic factor that can restrain excessive vascular budding and facilitate the expansion of blood vessel lumen, ultimately resulting in the fusion of blood vessels. IMD has protective roles in various diseases, including ischemia-reperfusion injury, metabolic disease, cardiovascular diseases and inflammatory diseases. This review systematically elucidates IMD's expression, structure, related receptors and signal pathway, as well as its comprehensive functions in the context of acute kidney injury, obesity, diabetes, heart failure and sepsis. However, the precise formation process of IMD short peptides in vivo and their downstream signaling pathway have not been fully elucidated yet. Further in-depth studies are need to translate IMD research into clinical applications.

Promising novel therapeutic targets for kidney disease: Emphasis on kidney-specific proteins

Worldwide, around 850 million people are diagnosed with kidney disease but the available treatment options are still limited. Preclinical studies propose a plethora of druggable targets that can attenuate kidney disease and could qualify as novel therapeutic strategies, although most of these targets still await clinical testing. Here, we review some promising candidate targets for chronic kidney disease: intermedin, periostin, sirtuin, the cannabinoid receptor, Klotho, and uromodulin. For acute kidney injury, we discuss Apelin, Elabela, growth differentiation factor-15, Fyn kinase, and Klotho. Target selection for further clinical development should consider redundancies with the standard of care, potential synergistic effects with existing treatments, as well as the potential of additional effects on the cardiovascular system as a common comorbidity in patients with kidney disease.

Renal Hypoxic Reperfusion Injury-on-Chip Model for Studying Combinational Vitamin Therapy

Renal ischemic-reperfusion injury decreases the chances of long-term kidney graft survival and may lead to the loss of a transplanted kidney. During organ excision, the cycle of warm ischemia from the donor and cold ischemia is due to storage in a cold medium after revascularization following organ transplantation. The reperfusion of the kidney graft activates several pathways that generate reactive oxygen species, forming a hypoxic-reperfusion injury. Animal models are generally used to model and investigate renal hypoxic-reperfusion injury. However, these models face ethical concerns and present a lack of robustness and intraspecies genetic variations, among other limitations. We introduce a microfluidics-based renal hypoxic-reperfusion (RHR) injury-on-chip model to overcome current limitations. Primary human renal proximal tubular epithelial cells and primary human endothelial cells were cultured on the apical and basal sides of a porous membrane. Hypoxic and normoxic cell culture media were used to create the RHR injury-on-chip model. The disease model was validated by estimating various specific hypoxic biomarkers of RHR. Furthermore, retinol, ascorbic acid, and combinational doses were tested to devise a therapeutic solution for RHR. We found that combinational vitamin therapy can decrease the chances of RHR injury. The proposed RHR injury-on-chip model can serve as an alternative to animal testing for injury investigation and the identification of new therapies.

Dexmedetomidine Attenuates Ferroptosis-Mediated Renal Ischemia/Reperfusion Injury and Inflammation by Inhibiting ACSL4 via α2-AR

Ischemia-reperfusion (I/R) injury is a serious clinical pathology associated with acute kidney injury (AKI). Ferroptosis is non-apoptotic cell death that is known to contribute to renal I/R injury. Dexmedetomidine (Dex) has been shown to exert anti-inflammatory and organ protective effects. This study aimed to investigate the detailed molecular mechanism of Dex protects kidneys against I/R injury through inhibiting ferroptosis. We established the I/R-induced renal injury model in mice, and OGD/R induced HEK293T cells damage in vitro. RNA-seq analysis was performed for identifying the potential therapeutic targets. RNA-seq analysis for differentially expressed genes (DEGs) reported Acyl-CoA synthetase long-chain family member 4 (ACSL4) related to ferroptosis and inflammation in I/R mice renal, which was validated in rodent renal. Liproxstatin-1, the specific small-molecule inhibitor of ferroptosis, significantly attenuated ferroptosis-mediated renal I/R injury with decreased LPO, MDA, and LDH levels, and increased GSH level. Inhibiting the activity of ACSL4 by the Rosiglitazone (ROSI) resulted in the decreased ferroptosis and inflammation, as well as reduced renal tissue damage, with decreasing LPO, MDA and LDH level, increasing GSH level, reducing COX2 and increasing GPx4 protein expression, and suppressing the TNF-α mRNA and IL-6 mRNA levels. Dex as a α2-adrenergic receptor (α2-AR) agonist performed renal protective effects against I/R-induced injury. Our results also revealed that Dex administration mitigated tissue damage, inhibited ferroptosis, and downregulated inflammation response following renal I/R injury, which were associated with the suppression of ACSL4. In addition, ACSL4 overexpression abolishes Dex-mediated protective effects on OGD/R induced ferroptosis and inflammation in HEK293T cells, and promotion of ACSL4 expression by α2-AR inhibitor significantly reversed the effects on the protective role of Dex. This present study indicated that the Dex attenuates ferroptosis-mediated renal I/R injury and inflammation by inhibiting ACSL4 via α2-AR.

Compensatory elevated serum intermedin levels are associated with increased vascular calcification in hemodialysis patients

INTRODUCTION

Vascular calcification (VC), which is a pathological process of abnormal calcium and phosphorus deposition in blood vessels, valves, heart and other tissues, is highly prevalent and predicts mortality in dialysis patients. Its mechanisms are complex and unclear. We presume that intermedin (IMD), a kind of small molecule active peptide, may play roles in VC in hemodialysis (HD) patients. This study aims to evaluate serum IMD levels and establish their relation to VC and other parameters in HD patients.

METHODS

A total of 116 patients on maintenance HD treatment and 52 age- and sex-matched healthy controls were enrolled in this study. Serum IMD levels were measured by radioimmunoassay (RIA). VC was evaluated by abdominal aortic calcification scores.

RESULTS

Serum IMD levels were significantly lower in HD patients than in controls [24.89 (13.55, 50.24) pg/ml vs. 137.79 (93.21, 201.64) pg/ml, P < 0.0001]. In addition, IMD was negatively correlated with the serum phosphate level (P = 0.036) in HD patients. However, compared with the group whose IMD levels were above the median, patients with IMD levels less than the median had a lower incidence of VC (P = 0.031). Multivariate logistic regression analyses revealed that serum IMD levels more than 24.89 pg/ml (P = 0.014, OR = 0.285), higher serum iPTH levels (P < 0.0001, OR = 1.093) and older age (P = 0.009, OR = 1.003) were significant independent determinant factors for VC in HD patients.

CONCLUSION

The serum IMD levels were significantly lower in HD patients than that in healthy group. In addition to higher PTH levels and older age, compensatory elevated IMD levels may be an independently determinant factor for VC in HD patients. This was the first study about IMD and VC in dialysis patients.

The genetic deletion of the Dual Specificity Phosphatase 3 (DUSP3) attenuates kidney damage and inflammation following ischaemia/reperfusion injury in mouse

AIM

Dual Specificity Phosphatase 3 (DUSP3) regulates the innate immune response, with a putative role in angiogenesis. Modulating inflammation and perfusion contributes to renal conditioning against ischaemia/reperfusion (I/R). We postulate that the functional loss of DUSP3 is associated with kidney resistance to I/R.

METHODS

Ten C57BL/6 male WT and Dusp3^-/- mice underwent right nephrectomy and left renal I/R (30 min/48 hours). Renal injury was assessed based on serum levels of urea (BUN) and Jablonski score. The expression of CD31 and VEGF vascular markers was quantified by RT-qPCR and immuno-staining. Renal resistivity index (RRI) was measured in vivo by Doppler ultrasound. Comparative phosphoproteomics was conducted using IMAC enrichment of phosphopeptides. Inflammatory markers were quantified at both mRNA and protein levels in ischaemic vs non-ischaemic kidneys in WT vs Dusp3^-/- .

RESULTS

At baseline, we located DUSP3 in renal glomeruli and endothelial cells. CD31-positive vascular network was significantly larger in Dusp3^-/- kidneys compared to WT, with a lower RRI in Dusp3^-/- mice. Following I/R, BUN and Jablonski score were significantly lower in Dusp3^-/- vs WT mice. Phosphoproteomics highlighted a down-regulation of inflammatory pathways and up-regulation of phospho-sites involved in cell metabolism and VEGF-related angiogenesis in Dusp3^-/- vs WT ischaemic kidneys. Dusp3^-/- ischaemic kidneys showed decreased mRNA levels of CD11b, TNF-α, KIM-1, IL-6, IL-1β and caspase-3 compared to controls. The numbers of PCNA-, F4-80- and CD11b-positive cells were reduced in Dusp3^-/- vs WT kidneys post-I/R.

CONCLUSION

Genetic inactivation of Dusp3 is associated with kidney conditioning against I/R, possibly due to attenuated inflammation and improved perfusion.

Intermedin Reduces Oxidative Stress and Apoptosis in Ventilator-Induced Lung Injury via JAK2/STAT3

Mechanical ventilation is an effective treatment for acute respiratory distress syndrome (ARDS), which can improve the prognosis of ARDS to a certain extent. However, it may further aggravate lung tissue injury, which is defined as ventilator-induced lung injury (VILI). Intermedin (IMD) belongs to the calcitonin gene-related peptide (CPRP) superfamily. Our previous studies have found that IMD reduces the expression proinflammatory cytokines, down-regulates nuclear translocation and improves the integrity of endothelial barrier in ARDS. However, the effect of IMD on VILI has not been clarified. Oxidative stress imbalance and apoptosis are the main pathophysiological characteristics of VILI. In the current study, we used C57B6/J mice and human pulmonary microvascular endothelial cells (HPMECs) to establish a VILI model to analyze the effects of IMD on VILI and explore its potential mechanism. We found that IMD alleviated lung injury and inflammatory response in VILI, mainly in reducing ROS levels, upregulating SOD content, downregulating MDA content, reducing the expression of Bax and caspase-3, and increasing the expression of Bcl-2. In addition, we also found that IMD played its anti-oxidative stress and anti-apoptotic effects via JAK2/STAT3 signaling. Our study may provide some help for the prevention and treatment of VILI.