Prorenin independently causes hypertension and renal and cardiac fibrosis in cyp1a1-prorenin transgenic rats

Pathway from Acute Kidney Injury to Chronic Kidney Disease: Molecules Involved in Renal Fibrosis

Acute kidney injury (AKI) is one of the main conditions responsible for chronic kidney disease (CKD), including end-stage renal disease (ESRD) as a long-term complication. Besides short-term complications, such as electrolyte and acid-base disorders, fluid overload, bleeding complications or immune dysfunctions, AKI can develop chronic injuries and subsequent CKD through renal fibrosis pathways. Kidney fibrosis is a pathological process defined by excessive extracellular matrix (ECM) deposition, evidenced in chronic kidney injuries with maladaptive architecture restoration. So far, cited maladaptive kidney processes responsible for AKI to CKD transition were epithelial, endothelial, pericyte, macrophage and fibroblast transition to myofibroblasts. These are responsible for smooth muscle actin (SMA) synthesis and abnormal renal architecture. Recently, AKI progress to CKD or ESRD gained a lot of interest, with impressive progression in discovering the mechanisms involved in renal fibrosis, including cellular and molecular pathways. Risk factors mentioned in AKI progression to CKD are frequency and severity of kidney injury, chronic diseases such as uncontrolled hypertension, diabetes mellitus, obesity and unmodifiable risk factors (i.e., genetics, older age or gender). To provide a better understanding of AKI transition to CKD, we have selected relevant and updated information regarding the risk factors responsible for AKIs unfavorable long-term evolution and mechanisms incriminated in the progression to a chronic state, along with possible therapeutic approaches in preventing or delaying CKD from AKI.

Targeting RNA-binding protein HuR to inhibit the progression of renal tubular fibrosis

BACKGROUND

Upregulation of an RNA-binding protein HuR has been implicated in glomerular diseases. Herein, we evaluated whether it is involved in renal tubular fibrosis.

METHODS

HuR was firstly examined in human kidney biopsy tissue with tubular disease. Second, its expression and the effect of HuR inhibition with KH3 on tubular injury were further assessed in a mouse model induced by a unilateral renal ischemia/reperfusion (IR). KH3 (50 mg kg-1) was given daily via intraperitoneal injection from day 3 to 14 after IR. Last, one of HuR-targeted pathways was examined in cultured proximal tubular cells.

RESULTS

HuR significantly increases at the site of tubular injury both in progressive CKD in patients and in IR-injured kidneys in mice, accompanied by upregulation of HuR targets that are involved in inflammation, profibrotic cytokines, oxidative stress, proliferation, apoptosis, tubular EMT process, matrix remodeling and fibrosis in renal tubulointerstitial fibrosis. KH3 treatment reduces the IR-induced tubular injury and fibrosis, accompanied by the remarkable amelioration in those involved pathways. A panel of mRNA array further revealed that 519 molecules in mouse kidney following IR injury changed their expression and 71.3% of them that are involved in 50 profibrotic pathways, were ameliorated when treated with KH3. In vitro, TGFβ1 induced tubular HuR cytoplasmic translocation and subsequent tubular EMT, which were abrogated by KH3 administration in cultured HK-2 cells.

CONCLUSIONS

These results suggest that excessive upregulation of HuR contributes to renal tubulointerstitial fibrosis by dysregulating genes involved in multiple profibrotic pathways and activating the TGFß1/HuR feedback circuit in tubular cells. Inhibition of HuR may have therapeutic potential for renal tubular fibrosis.

Integrated whole transcriptome analysis for the crucial regulators and functional pathways related to cardiac fibrosis in rats

BACKGROUND

Cardiac fibrosis has gradually gained significance in the field of cardiovascular disease; however, its specific pathogenesis remains unclear. This study aims to establish the regulatory networks based on whole-transcriptome RNA sequencing analyses and reveal the underlying mechanisms of cardiac fibrosis.

METHODS

An experimental model of myocardial fibrosis was induced using the chronic intermittent hypoxia (CIH) method. Expression profiles of long non-coding RNA (lncRNA), microRNA (miRNA), and messenger RNA (mRNA) were acquired from right atrial tissue samples of rats. Differentially expressed RNAs (DERs) were identified, and functional enrichment analysis was performed. Moreover, a protein-protein interaction (PPI) network and competitive endogenous RNA (ceRNA) regulatory network that are related to cardiac fibrosis were constructed, and the relevant regulatory factors and functional pathways were identified. Finally, the crucial regulators were validated using qRT-PCR.

RESULTS

DERs, including 268 lncRNAs, 20 miRNAs, and 436 mRNAs, were screened. Further, 18 relevant biological processes, such as "chromosome segregation, " and 6 KEGG signaling pathways, such as "cell cycle, " were significantly enriched. The regulatory relationship of miRNA-mRNA-KEGG pathways showed eight overlapping disease pathways, including "pathways in cancer." In addition, crucial regulatory factors, such as Arnt2, WNT2B, GNG7, LOC100909750, Cyp1a1, E2F1, BIRC5, and LPAR4, were identified and verified to be closely related to cardiac fibrosis.

CONCLUSION

This study identified the crucial regulators and related functional pathways in cardiac fibrosis by integrating the whole transcriptome analysis in rats, which might provide novel insights into the pathogenesis of cardiac fibrosis.

Hormone-Dependent Regulation of Renin and Effects on Prorenin Receptor Signaling in the Collecting Duct

The production of renin by the principal cells of the collecting duct has widened our understanding of the regulation of intrarenal angiotensin II (Ang II) generation and blood pressure. In the collecting duct, Ang II increases the synthesis and secretion of renin by mechanisms involving the activation of Ang II type 1 receptor (AT1R) via stimulation of the PKCα, Ca²⁺, and cAMP/PKA/CREB pathways. Additionally, paracrine mediators, including vasopressin (AVP), prostaglandins, bradykinin (BK), and atrial natriuretic peptide (ANP), regulate renin in principal cells. During Ang II-dependent hypertension, despite plasma renin activity suppression, renin and prorenin receptor (RPR) are upregulated in the collecting duct and promote de novo formation of intratubular Ang II. Furthermore, activation of PRR by its natural agonists, prorenin and renin, may contribute to the stimulation of profibrotic factors independent of Ang II. Thus, the interactions of RAS components with paracrine hormones within the collecting duct enable tubular compartmentalization of the RAS to orchestrate complex mechanisms that increase intrarenal Ang II, Na+ reabsorption, and blood pressure.

Oxidative Stress and Inflammation Are Associated with Coexistent Severe Multivessel Coronary Artery Stenosis and Right Carotid Artery Severe Stenosis in Elderly Patients

Oxidative stress and inflammatory response are the main pathogenic pathways in atherosclerosis stenosis. This study is aimed at evaluating the roles of oxidative stress and inflammatory response in coexistent right carotid artery severe stenosis and severe multivessel coronary artery stenosis in elderly patients. Circulating levels of total oxidant status (TOS), lipid hydroperoxide (LHP), 8-isoprostane (8-IP), malondialdehyde (MDA), monocyte chemotactic protein-4 (MCP-4), amyloid A (AA), high-sensitivity C-reactive protein (hs-CRP), and tumor necrosis factor-α (TNF-α) were measured by standardised laboratory test methods. Markers of oxidative stress and inflammatory response: levels of TOS, LHP, 8-IP, MDA, MCP-4, AA, hs-CRP, and TNF-α, were increased (P < 0.001) in elderly patient. These results suggested that oxidative stress and inflammatory response may be involved in carotid artery severe stenosis and severe multivessel coronary artery stenosis and measuring oxidative stress and inflammation biomarkers may also be a promising step in the development of an effective method for monitoring the severity of right carotid artery stenosis and multivessel coronary artery stenosis in elderly patients.

Inflammatory cytokines levels in aqueous humour and surgical outcomes of trabeculectomy in patients with prior acute primary angle closure

PURPOSE

To quantify the levels of three inflammatory cytokines in the aqueous humour of patients with prior acute primary angle closure (APAC) and investigate their correlation with surgical outcomes of trabeculectomy.

METHODS

In this prospective cohort study, aqueous humour samples were collected from 44 prior APAC eyes. Analyte concentrations of monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6) were measured using multiplexed immunoassay kits. Intraocular pressure was measured using Goldmann application tonometry.

RESULTS

Forty-four prior APAC eyes were followed up for 24 months after trabeculectomy and divided into success and failure groups according to surgical outcomes. Monocyte chemoattractant protein-1 (MCP-1) levels in the aqueous humour were significantly higher in the failure group (p = 0.0118). Univariate and multivariate analyses showed that MCP-1 level was a significant risk factor for trabeculectomy outcomes (univariate analysis: p = 0.016, odds ratio = 14.538; multivariate analysis: p = 0.023, odds ratio = 13.718). When prior APAC eyes were divided according to MCP-1 levels, the overall success rate was significantly higher in eyes with low MCP-1 levels than eyes with high MCP-1 levels (p = 0.0249).

CONCLUSION

In prior APAC patients, the MCP-1 level in the aqueous humour predicts trabeculectomy results. Therefore, modulation of MCP-1 expression may have potential clinical applications after filtration surgery.

Key role for EphB2 receptor in kidney fibrosis

Erythropoietin producing hepatocellular (Eph)-Eph receptor interacting (Ephrin) receptor-ligand signaling has been implicated in the development of tissue fibrosis, though it has not been well defined in the kidney. We detected substantial up-regulation of expression and phosphorylation of the EphB2 receptor tyrosine kinase in fibrotic kidney tissue obtained both from mice subjected to the unilateral renal ischemia-reperfusion (IR) model at 14 days and in patients suffering from chronic kidney disease (CKD). Knockout (KO) mice lacking EphB2 expression exhibited a normal renal structure and function, indicating no major role for this receptor in kidney development or action. Although IR injury is well-known to cause tissue damage, fibrosis, and renal dysfunction, we found that kidneys from EphB2KO mice showed much less renal tubular injury and retained a more preserved renal function. IR-injured kidneys from EphB2 KOs exhibited greatly reduced fibrosis and inflammation compared with injured wildtype (WT) littermates, and this correlated with a significant reduction in renal expression of profibrotic molecules, inflammatory cytokines, NADPH oxidases, and markers for cell proliferation, tubular epithelial-to-mesenchymal transition (EMT), myofibroblast activation, and apoptosis. A panel of 760 fibrosis-associated genes were further assessed, revealing that 506 genes in WT mouse kidney following IR injury changed their expression. However, 70.9% of those genes were back to or close to normal in expression when EphB2 was deleted. These data indicate that endogenous EphB2 expression and signaling are abnormally activated after kidney injury and subsequently contribute to the development of renal fibrosis via regulation of multiple profibrotic pathways.

Yes-Associated Protein is Involved in Myocardial Fibrosis in Rats with Diabetic Cardiomyopathy

INTRODUCTION

Recent studies have shown that YAP is closely related to the pathological process of cardiovascular diseases. But the role of YAP in cardiac injury of diabetic cardiomyopathy (DCM) is still unclear.

METHODS

Diabetic cardiomyopathy rat model was established and divided into control group, DCM group, LV-SC-shRNA group and LV-YAP-shRNA group. LV-SC-shRNA group and LV-YAP-shRNA group were injected with lentivirus expressing SC-shRNA and YAP-shRNA via tail vein, respectively. Primary rat cardiac fibroblasts (CFs) were stimulated with high concentration of glucose and treated with recombinant lentivirus expressing either SC-shRNA or YAP-shRNA to observe the expression of CTGF and fibronectin, so as to observe the effect of inhibiting YAP on the pathogenesis of DCM.

RESULTS

Compared with control group, high glucose markedly increased YAP mRNA and protein expression in DCM and CFs. Inhibition of YAP decreased myocardial fibrosis and improved cardiac function in the DCM model and decreased the expression of CTGF and fibronectin in CFs. The result suggested that YAP plays a key role in the pathological progression of DCM, and the underlying mechanisms may be associated with TEAD and CTGF.

DISCUSSION

We found that the expression of YAP was increased both in vivo and in vitro, suggesting that YAP is closely related to DCM, and YAP knockdown can reduce myocardial fibrosis in rat model of DCM by reducing the expression of PAI-1, collagen I, collagen III, CTGF and profilin, as well as the expression of CTGF and fibronectin in CFs. This study revealed that YAP plays an important role in the pathological process of diabetic cardiomyopathy, and down-regulation of YAP expression may provide a new therapeutic target for DCM.

Targeting the renin-angiotensin-aldosterone system in fibrosis

Fibrosis is characterized by excessive deposition of extracellular matrix components such as collagen in tissues or organs. Fibrosis can develop in the heart, kidneys, liver, skin or any other body organ in response to injury or maladaptive reparative processes, reducing overall function and leading eventually to organ failure. A variety of cellular and molecular signaling mechanisms are involved in the pathogenesis of fibrosis. The renin-angiotensin-aldosterone system (RAAS) interacts with the potent Transforming Growth Factor β (TGFβ) pro-fibrotic pathway to mediate fibrosis in many cell and tissue types. RAAS consists of both classical and alternative pathways, which act to potentiate or antagonize fibrotic signaling mechanisms, respectively. This review provides an overview of recent literature describing the roles of RAAS in the pathogenesis of fibrosis, particularly in the liver, heart, kidney and skin, and with a focus on RAAS interactions with TGFβ signaling. Targeting RAAS to combat fibrosis represents a promising therapeutic approach, particularly given the lack of strategies for treating fibrosis as its own entity, thus animal and clinical studies to examine the impact of natural and synthetic substances to alter RAAS signaling as a means to treat fibrosis are reviewed as well.

Sirtuins: Developing Innovative Treatments for Aged-Related Memory Loss and Alzheimer's Disease

The world's population continues to age at a rapid pace. By the year 2050, individuals over the age of 65 will account for sixteen percent of the world's population and life expectancy will increase well over eighty years of age. Accompanied by the aging of the global population is a significant rise in Non-Communicable Diseases (NCDs). Neurodegenerative disorders will form a significant component for NCDs. Currently, dementia is the 7th leading cause of death and can be the result of multiple causes that include diabetes mellitus, vascular disease, and Alzheimer's Disease (AD). AD may represent at least sixty percent of these cases. Current treatment for these disorders is extremely limited to provide only some symptomatic relief at present. Sirtuins and in particular, the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), represent innovative strategies for the treatment of cognitive loss. New work has revealed that SIRT1 provides protection against memory loss through mechanisms that involve oxidative stress, Aβ toxicity, neurofibrillary degeneration, vascular injury, mitochondrial dysfunction, and neuronal loss. In addition, SIRT1 relies upon other avenues that can include trophic factors, such as erythropoietin, and signaling pathways, such as Wnt1 inducible signaling pathway protein 1 (WISP1/CCN4). Yet, SIRT1 can have detrimental effects as well that involve tumorigenesis and blockade of stem cell differentiation and maturation that can limit reparative processes for cognitive loss. Further investigations with sirtuins and SIRT1 should be able to capitalize upon these novel targets for dementia and cognitive loss.