Human podocyte injury in the early course of hypertensive renal injury

Blood Pressure Management Strategies and Podocyte Health

Hypertension (HTN) is one of the key global cardiovascular risk factors, which is tightly linked to kidney health and disease development. Podocytes, glomerular epithelial cells that play a pivotal role in maintenance of the renal filtration barrier, are significantly affected by increased glomerular capillary pressure in HTN. Damage or loss of these cells causes proteinuria, which marks the initiation of the HTN-driven renal damage. It goes without saying that effective blood pressure (BP) management should not only mitigate cardiovascular risks but also preserve renal function by protecting podocyte integrity. This review offers a comprehensive examination of current BP management strategies and their implications for podocyte structure and function and emphasizes strategies for the reduction of proteinuria in HTN. We explore primary and secondary antihypertensive agents, including angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, and diuretics, as well as newer therapies (sodium-glucose cotransporter-2 blocking and endothelin receptor antagonism), emphasizing their mechanistic roles in safeguarding podocytes and curtailing proteinuria.

Mechanistic Insights Into Redox Damage of the Podocyte in Hypertension

Podocytes are specialized cells within the glomerular filtration barrier, which are crucial for maintaining glomerular structural integrity and convective ultrafiltration. Podocytes exhibit a unique arborized morphology with foot processes interfacing by slit diaphragms, ladder-like, multimolecular sieves, which provide size and charge selectivity for ultrafiltration and transmembrane signaling. Podocyte dysfunction, resulting from oxidative stress, dysregulated prosurvival signaling, or structural damage, can drive the development of proteinuria and glomerulosclerosis in hypertensive nephropathy. Functionally, podocyte injury leads to actin cytoskeleton rearrangements, foot process effacement, dysregulated slit diaphragm protein expression, and impaired ultrafiltration. Notably, the renin-angiotensin system plays a pivotal role in podocyte function, with beneficial AT2R (angiotensin receptor 2)-mediated nitric oxide (NO) signaling to counteract AT1R (angiotensin receptor 1)-driven calcium (Ca2+) influx and oxidative stress. Disruption of this balance contributes significantly to podocyte dysfunction and drives albuminuria, a marker of kidney damage and overall disease progression. Oxidative stress can also lead to sustained ion channel-mediated Ca2+ influx and precipitate cytoskeletal disorganization. The complex interplay between GPCR (G-protein coupled receptor) signaling, ion channel activation, and redox injury pathways underscores the need for additional research aimed at identifying targeted therapies to protect podocytes and preserve glomerular function. Earlier detection of albuminuria and podocyte injury through routine noninvasive diagnostics will also be critical in populations at the highest risk for the development of hypertensive kidney disease. In this review, we highlight the established mechanisms of oxidative stress-mediated podocyte damage in proteinuric kidney diseases, with an emphasis on a hypertensive renal injury. We will also consider emerging therapies that have the potential to selectively protect podocytes from redox-related injury.

Advance on Chinese Medicine for Hypertensive Renal Damage: Focus on the Complex Molecular Mechanisms

Hypertensive renal damage (HRD) is a major cause of end-stage renal disease. Among the causes of end-stage renal disease, HRD accounts for nearly 34% of the total number of cases. Antihypertensive treatment is primarily drug-based, but therapeutic efficacy is less effective and can have serious side effects. Chinese medicine (CM) has significant advantages in the treatment of HRD. CM is rich in various active ingredients and has the property of targeting multiple targets and channels. Therefore, the regulatory network of CM on disease is complex. A large number of CM have been employed to treat HRD, either as single applications or as part of compound formulations. The key possible mechanisms of CM for HRD include regulation of the renin-angiotensin-aldosterone system, antioxidation, anti-inflammation, rescue of endothelial function, regulation of vasoactive substance secretion and obesity-related factors, etc. This review summarized and discussed the recent advance in the basic research mechanisms of CM interventions for HRD and pointed out the challenges and future prospects.

Urinary nephrin-a potential marker of early glomerular injury: a systematic review and meta-analysis

BACKGROUND

Both early recognition of glomerular injury and diagnosis of renal injury remain important problems in clinical settings, and current diagnostic biomarkers have limitations. The aim of this review was to determine the diagnostic accuracy of urinary nephrin for detecting early glomerular injury.

METHODS

A search was conducted through electronic databases for all relevant studies published until January 31, 2022. The methodological quality was evaluated using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Pooled sensitivity, specificity, and other estimates of diagnostic accuracy were determined using a random effect model. The Summary Receiver Operating Characteristics (SROC) was used to pool the data and to estimate the area under the curve (AUC).

RESULTS

The meta-analysis included 15 studies involving 1587 participants. Overall, the pooled sensitivity of urinary nephrin for detecting glomerular injury was 0.86 (95% CI 0.83-0.89) and specificity was 0.73 (95% CI 0.70-0.76). The AUC-SROC to summarise the diagnostic accuracy was 0.90. As a predictor of preeclampsia, urinary nephrin showed a sensitivity of 0.78 (95% CI 0.71-0.84) and specificity of 0.79 (95% CI 0.75-0.82), and as a predictor of nephropathy the sensitivity was 0.90 (95% CI 0.87-0.93), and specificity was 0.62 (95% CI 0.56-0.67). A subgroup analysis using ELISA as a method of diagnosis showed a sensitivity of 0.89 (95% CI 0.86-0.92), and a specificity of 0.72 (95% CI 0.69-0.75).

CONCLUSION

Urinary nephrin may be a promising marker for the detection of early glomerular injury. ELISA assays appear to provide reasonable sensitivity and specificity. Once translated into clinical practice, urinary nephrin could provide an important addition to a panel of novel markers to help in the detection of acute and chronic renal injury.

URINARY NEPHRIN AS AN EARLY BIOMARKER OF HYPERTENSIVE NEPHROPATHY

Hypertensive nephropathy (HN) is characterized by kidney damage due to chronic high blood pressure. Podocytes play a crucial role in the pathogenesis of HN, thus, nephrin could be important in the early diagnosis of HN. The aim of the study was to investigate the association of urinary nephrin (u-nephrin) levels with clinical and laboratory characteristics in patients with HN and to test diagnostic relevance of u-nephrin as an early biomarker of HN. In this cross-sectional study, 114 subjects were recruited, 84 patients with chronic hypertension (CH) and 30 healthy controls. All patients with CH were classified according to the urinary microalbumin/creatinine ratio (UM/CR) and according to the chronic kidney disease (CKD) stage. Urine samples were collected to estimate the u-nephrin level by ELISA and to determine UM/CR. Blood samples were used for biochemical analyses. We found elevated u-nephrin in 78.3% of normoalbuminuric subjects with CH. The levels of u-nephrin increased gradually with the stage of CKD. ROC curve plotted for u-nephrin showed 89.7% sensitivity and 88.8% specificity, while UM/CR showed a sensitivity of 44.8% and specificity of 86.1% to detect HN in the early stage. It is concluded that u-nephrin can be useful as an early biomarker of HN.

Qian Yang Yu Yin granule improves hypertensive renal damage: A potential role for TRPC6-CaMKKβ-AMPK-mTOR-mediated autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Qian Yang Yu Yin granules (QYYYG) have a long history in the treatment of hypertensive renal damage (HRD) in China. Clinical studies have found that QYYYG stabilizes blood pressure and prevents early renal damage. However, the exact mechanism is not entirely clear.

AIM OF THE STUDY

To evaluate the therapeutic effect and further explore the therapeutic mechanism of QYYYG against HRD.

MATERIALS AND METHODS

The efficacy of QYYYG in treating HRD was assessed in spontaneous hypertension rats (SHR). Renal autophagy and the TRPC6-CaMKKβ-AMPK pathway in rats were evaluated. The regulatory role of QYYYG in angiotensin II (Ang II) induced abnormal autophagy in rat podocytes was determined by detecting autophagy-related proteins, intracellular Ca²⁺ content, and the TRPC6-CaMKKβ-AMPK-mTOR pathway expressions. Finally, we established a stable rat podocyte cell line overexpressing TRPC6 and used the cells to verify the regulatory effects of QYYYG.

RESULTS

QYYYG alleviated HRD and reversed the abnormal expression of autophagy-related genes in the SHR. In vitro, QYYYG protected against Ang II-induced podocyte damage. Furthermore, treatment of podocytes with QYYYG reversed Ang II-induced autophagy and inhibited Ang II-stimulated TRPC6 activation, Ca²⁺ influx and activation CaMKKβ-AMPK pathway. Overexpression of TRPC6 resulted in pronounced activation of CaMKKβ, AMPK, and autophagy induction in rat podocytes, which were significantly attenuated by QYYYG.

CONCLUSIONS

The present study suggested that QYYYG may exert its HRD protective effects in part by regulating the abnormal autophagy of podocytes through the TRPC6-CaMKKβ-AMPK-mTOR pathway.

Nephrinuria and podocytopathies

The discovery of nephrin in 1998 has launched a new era in glomerular diseases research, emphasizing its crucial role in the structure and function of the glomerular filtration barrier. In the past 20 years, substantial advances have been made in understanding podocyte structure and function as well as the discovery of several podocyte-related proteins including nephrin. The glomerular filtration barrier is comprised of podocytes, the glomerular basement membrane and endothelial cells. Podocytes, with their specialized slit diaphragm, form the essential backbone of the glomerular filtration barrier. Nephrin is a crucial structural and functional feature of the slit diaphragm that prevents plasma protein, blood cell and macromolecule leakage into the urine. Podocyte damage results in nephrin release. Podocytopathies are kidney diseases in which podocyte damage drives proteinuria, i.e., nephrotic syndrome. Many kidney diseases involve podocytopathy including congenital nephrotic syndrome of Finnish type, diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, collapsing glomerulonephropathy, diabetic nephropathy, lupus nephropathy, hypertensive nephropathy and preeclampsia. Recently, urinary nephrin measurement has become important in the early detection of podocytopathies. In this chapter, we elaborate the main structural and functional features of nephrin as a podocyte-specific protein, pathomechanisms of podocytopathies which result in nephrinuria, highlight the most commonly used methods for detecting urinary nephrin and investigate the diagnostic, prognostic and potential therapeutic relevance of urinary nephrin in primary and secondary proteinuric kidney diseases.

miR-188-5p Promotes Tumor Growth by Targeting CD2AP Through PI3K/AKT/mTOR Signaling in Children with Acute Promyelocytic Leukemia

PURPOSE

Pediatric acute promyelocytic leukemia (APL) accounts for 10% of pediatric acute myelogenous leukemia (AML) case and is accompanied by a tendency to hemorrhage. miR-188-5p plays an important role in adult AML. Therefore, the purpose of this study was to explore the effects of miR-188-5p on cell proliferation and apoptosis and tumor growth, and its mechanism in pediatric APL patients.

MATERIALS AND METHODS

Survival-associated miRNAs or mRNAs from TCGA database associated with AML were identified via using the "survival R" package in R language. CCK8, clone formation, flow cytometry, RT-PCR, immunohistochemistry and Western blot assays were used to detect the viability, proliferation, apoptosis, cell cycle, and related gene expression in APL cell lines. The prognostic value of miR-188-5p was evaluated using a ROC curve. The tumorigenic ability of APL cell lines was determined using a nude mouse transplantation tumor experiment. Tumor cell apoptosis was determined by TUNEL assay in vivo. The target genes of miR-188-5p were predicted using the miRDB, miRTarBase, and TargetScan databases. A PPI network was constructed using STRING database and the hub gene was identified using the MCODE plug-in of the Cytoscape software. The DAVID database was used to perform GO and KEGG pathway enrichment analyses. A luciferase reporter assay was used to demonstrate the binding of miR-188-5p to CD2AP.

RESULTS

miR-188-5p overexpression or CD2 associated protein (CD2AP) inhibition was significantly associated with poor survival in pediatric APL patients. Upregulation of miR-188-5p was identified in the blood of pediatric APL patients and cell lines. Increased expression of miR-188-5p also promoted the viability, proliferation, and cell cycle progression, and reduced the apoptosis of APL cells. Additionally, upregulation of miR-188-5p regulated the expressions of cyclinD1, p53, Bax, Bcl-2 and cleaved caspase-3. The area under the ROC curve (AUC) of miR-188-5p was 0.661. miR-188-5p overexpression increased the tumorigenic ability of APL and Ki67 expression, and reduced cell apoptosis in vivo. CD2AP was identified as the only overlapping gene from the list of miR-188-5p target genes and survival-related mRNAs of the TCGA database. It was mainly enriched in the "biological process (BP)" and "cellular component (CC)" terms, and was downregulated in the blood of pediatric APL patients and cell lines. The luciferase reporter, RT-PCR, and Western blot assays demonstrated that the binding of miR-188-5p to CD2AP. CD2AP inhibition promoted the proliferation and inhibited the apoptosis of APL cells. Rescue experiments showed that inhibition of miR-188-5p inhibited cell proliferation, activated the PI3K/AKT/mTOR signaling pathway, induced G0/G1 phase arrest, regulated gene expression, and promoted cell apoptosis, which were reversed by CD2AP inhibition.

CONCLUSION

miR-188-5p, an oncogene, promoted tumor growth and progression of pediatric APL in vitro and in vivo via targeting CD2AP and activating the PI3K/AKT/mTOR signaling pathway.