The level of urinary semaphorin3A is associated with disease activity in patients with minimal change nephrotic syndrome

Role of Semaphorin 3A in Kidney Development and Diseases

Kidney diseases are worldwide public health problems affecting millions of people. However, there are still limited therapeutic options against kidney diseases. Semaphorin 3A (SEMA3A) is a secreted and membrane-associated protein, which regulates diverse functions, including immune regulation, cell survival, migration and angiogenesis, thus involving in the several pathogeneses of diseases, including eyes and neurons, as well as kidneys. SEMA3A is expressed in podocytes and tubular cells in the normal adult kidney, and recent evidence has revealed that excess SEMA3A expression and the subsequent signaling pathway aggravate kidney injury in a variety of kidney diseases, including nephrotic syndrome, diabetic nephropathy, acute kidney injury, and chronic kidney disease. In addition, several reports have demonstrated that the inhibition of SEMA3A ameliorated kidney injury via a reduction in cell apoptosis, fibrosis and inflammation; thus, SEMA3A may be a potential therapeutic target for kidney diseases. In this review article, we summarized the current knowledge regarding the role of SEMA3A in kidney pathophysiology and their potential use in kidney diseases.

Semaporin3A-inhibitor ameliorates renal fibrosis through the regulation of JNK signaling

Renal fibrosis is the common pathological pathway in progressive renal diseases. In the study, we analyzed the roles of Semaphorin 3A (SEMA3A) on renal fibrosis and the effect of SEMA3A-inhibitor (SEMA3A-I) using unilateral ureteral obstruction (UUO) mouse model. The expression of SEMA3A in the proximal tubulus and neuropilin-1 (NRP1), a recepor of SEMA3A, in fibloblast and tubular cells were increased in the UUO kidneys. The increased expression of myofibroblast marker tenascin-C and fibronection as well as renal fibrosis were increased in UUO kidneys, all of which were ameliorated by SEMA3A-I. In addition, c-Jun N-terminal kinase (JNK) signaling pathway known as the target of SEMA3A signaling, was activated in proximal tubular cells and fibroblast cells after UUO surgery while SEMA3A-I significantly attenuated the activation. In vitro, treatments with SEMA3A as well as transforming growth factor-β1 (TGF-β1) in human proximal tubular cells lost epithelial cell characters while SEMA3A-I significantly ameliorated this transformation. JNK inhibitor, SP600125, partially reversed SEMA3A and TGF-β1-induced cell transformation, indicating that JNK signaling is involved in SEMA3A-induced renal fibrosis. In addition, the treatment with SEMA3A in fibroblast cells activated the expression of tenascin-C, collagen type I and fibronection, indicating that SEMA3A may accelerate renal fibrosis through the activation of fibroblast cells. The analysis of human data revealed the positive correlation between urinary SEMA3A and urinary N-acetyl-β-D-glucosaminidase, indicating the association between SEMA3A and tubular injury. In conclusion, SEMA3A signaling is involved in renal fibrosis through JNK signaling pathway and SEMA3A-I might be the therapeutic option for protecting from renal fibrosis.

MicroRNAs as Biomarkers for Nephrotic Syndrome

Nephrotic syndrome represents the clinical situation characterized by presence of massive proteinuria and low serum protein caused by a variety of diseases, including minimal change nephrotic syndrome (MCNS), focal segmental glomerulosclerosis (FSGS) and membranous glomerulonephropathy. Differentiating between diagnoses requires invasive renal biopsies in general. Even with the biopsy, we encounter difficulties to differentiate MCNS and FSGS in some cases. There is no other better option currently available for the diagnosis other than renal biopsy. MicroRNAs (miRNAs) are no-coding RNAs of approximately 20 nucleotides in length, which regulate target genes in the post-transcriptional processes and have essential roles in many diseases. MiRNAs in serum and urine have been shown as non-invasive biomarkers in multiple diseases, including renal diseases. In this article, we summarize the current knowledge of miRNAs as the promising biomarkers for nephrotic syndrome.

Semaphorin3A-Inhibitor Ameliorates Doxorubicin-Induced Podocyte Injury

Podocyte injury is an independent risk factor for the progression of renal diseases. Semaphorin3A (SEMA3A), expressed in podocytes and tubular cells in the mammalian adult kidneys, has been reported to regulate diverse biological functions and be associated with renal diseases. Here, we investigated pathological roles of SEMA3A signaling on podocyte injury using a doxorubicin (Dox)-induced mouse model and examined the therapeutic effect of SEMA3A-inhibitor (SEMA3A-I). We demonstrated that Dox caused massive albuminuria and podocyte apoptosis as well as an increase of SEMA3A expression in podocytes, all of which were ameliorated with SEMA3A-I treatment. In addition, c-Jun N-terminal kinase (JNK), known as a downstream of SEMA3A signaling, was activated in Dox-injected mouse podocytes while SEMA3A-I treatment partially blocked the activation. In vitro, SEMA3A-I protected against Dox-induced podocyte apoptosis and recombinant SEMA3A caused podocyte apoptosis with activation of JNK signaling. JNK inhibitor, SP600125, attenuated SEMA3A-induced podocyte apoptosis, indicating that the JNK pathway would be involved in SEMA3A-induced podocyte apoptosis. Furthermore, the analysis of human data revealed a positive correlation between levels of urinary SEMA3A and protein, suggesting that SEMA3A is associated with podocyte injury. In conclusion, SEMA3A has essential roles in podocyte injury and it would be the therapeutic target for protecting from podocyte injury.