GDF-15 Suppresses Puromycin Aminonucleoside-Induced Podocyte Injury by Reducing Endoplasmic Reticulum Stress and Glomerular Inflammation.

GDF15, also known as MIC1, is a member of the TGF-beta superfamily. Previous studies reported elevated serum levels of GDF15 in patients with kidney disorder, and its association with kidney disease progression, while other studies identified GDF15 to have protective effects. To investigate the potential protective role of GDF15 on podocytes, we first performed in vitro studies using a Gdf15-deficient podocyte cell line. The lack of GDF15 intensified puromycin aminonucleoside (PAN)-triggered endoplasmic reticulum stress and induced cell death in cultivated podocytes. This was evidenced by elevated expressions of Xbp1 and ER-associated chaperones, alongside AnnexinV/PI staining and LDH release. Additionally, we subjected mice to nephrotoxic PAN treatment. Our observations revealed a noteworthy increase in both GDF15 expression and secretion subsequent to PAN administration. Gdf15 knockout mice displayed a moderate loss of WT1+ cells (podocytes) in the glomeruli compared to wild-type controls. However, this finding could not be substantiated through digital evaluation. The parameters of kidney function, including serum BUN, creatinine, and albumin-creatinine ratio (ACR), were increased in Gdf15 knockout mice as compared to wild-type mice upon PAN treatment. This was associated with an increase in the number of glomerular macrophages, neutrophils, inflammatory cytokines, and chemokines in Gdf15-deficient mice. In summary, our findings unveil a novel renoprotective effect of GDF15 during kidney injury and inflammation by promoting podocyte survival and regulating endoplasmic reticulum stress in podocytes, and, subsequently, the infiltration of inflammatory cells via paracrine effects on surrounding glomerular cells.

Macrophage-Specific MCPIP1/Regnase-1 Attenuates Kidney Ischemia-Reperfusion Injury by Shaping the Local Inflammatory Response and Tissue Regeneration.

Sterile inflammation either resolves the initial insult or leads to tissue damage. Kidney ischemia/reperfusion injury (IRI) is associated with neutrophilic infiltration, enhanced production of inflammatory mediators, accumulation of necrotic cells and tissue remodeling. Macrophage-dependent microenvironmental changes orchestrate many features of the immune response and tissue regeneration. The activation status of macrophages is influenced by extracellular signals, the duration and intensity of the stimulation, as well as various regulatory molecules. The role of macrophage-derived monocyte chemoattractant protein-induced protein 1 (MCPIP1), also known as Regnase-1, in kidney ischemia-reperfusion injury (IRI) and recovery from sterile inflammation remains unresolved. In this study, we showed that macrophage-specific Mcpip1 deletion significantly affects the kidney phenotype. Macrophage-specific Mcpip1 transgenic mice displayed enhanced inflammation and loss of the tubular compartment upon IRI. We showed that MCPIP1 modulates sterile inflammation by negative regulation of Irf4 expression and accumulation of IRF4+ cells in the tissue and, consequently, suppresses the post-ischemic kidney immune response. Thus, we identified MCPIP1 as an important molecular sentinel of immune homeostasis in experimental acute kidney injury (AKI) and renal fibrosis.

The Involvement of MicroRNAs in Modulation of Innate and Adaptive Immunity in Systemic Lupus Erythematosus and Lupus Nephritis.

Noncoding RNAs (ncRNAs), including microRNAs (miRNAs), represent a family of RNA molecules that do not translate into protein. Nevertheless, they have the ability to regulate gene expression and play an essential role in immune cell differentiation and function. MicroRNAs were found to be differentially expressed in various tissues, and changes in their expression have been associated with several pathological processes. Yet, their roles in systemic lupus erythematosus (SLE) and lupus nephritis (LN) remain to be elucidated. Both SLE and LN are characterized by a complex dysfunction of the innate and adaptive immunity. Recently, significant findings have been made in understanding SLE through the use of genetic variant identification and expression pattern analysis and mouse models, as well as epigenetic analyses. Abnormalities in immune cell responses, cytokine and chemokine production, cell activation, and apoptosis have been linked to a unique expression pattern of a number of miRNAs that have been implicated in the immune pathogenesis of this autoimmune disease. The recent evidence that significantly increased the understanding of the pathogenesis of SLE drives a renewed interest in efficient therapy targets. This review aims at providing an overview of the current state of research on the expression and role of miRNAs in the immune pathogenesis of SLE and LN.