Mesenchymal Stem Cell-Derived Exosomes Attenuate Epithelial-Mesenchymal Transition of HK-2 Cells.

Renal fibrosis (RF) predisposes patients to an increased risk of progressive chronic kidney disease, and effective treatments remain elusive. Mesenchymal stem cell (MSC)-derived exosomes are considered a new treatment for tissue damage. Our study aimed to investigate the in vitro effects of bone marrow MSC-derived exosomes (BM-MSC-Exs) on transforming growth factor-ß1 (TGF-ß1)-induced fibrosis in renal tubular epithelial cells (HK-2 cells) and the associated mechanisms. Herein, we found BM-MSC-Exs could inhibit TGF-ß1-induced epithelial-mesenchymal transition (EMT) in HK-2 cells, and may involve autophagy activation of BM-MSC-Exs. Moreover, we first reported that after ceria nanoparticles (CeNPs) treatment, the improvements induced by BM-MSC-Ex on EMT were significantly enhanced by upregulating the expression of Nedd4Lof MSCs and promoting the secretion of exosomes, which contained Nedd4L. In addition, Nedd4L could activate autophagy in HK-2 cells. In conclusion, BM-MSC-Ex prevents the TGF-ß1-induced EMT of renal tubular epithelial cells by transporting Nedd4L, which activates autophagy. The results of this in vitro experiment may extend to RF, whereby BM-MSC-Ex may also be used as a novel treatment for improving RF. Impact statement Renal fibrosis (RF) is an important pathological change in chronic kidney disease that ultimately leads to end-stage renal failure, and effective treatments remain elusive. In this study, there are two contributions. First, our results suggest that bone marrow mesenchymal stem cell-derived exosomes (BM-MSC-Exs) can prevent transforming growth factor-ß1 (TGF-ß1)-induced epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells through Nedd4L trafficking, which activates autophagy. Second, the improvement effects of BM-MSC-Ex on TGF-ß1-induced HK-2 EMT can be enhanced by ceria nanoparticles (CeNPs). The findings in this study may be extended to RF: BM-MSC-Exs may be used as a novel treatment to improve RF.

A novel role of BK potassium channel activity in preventing the development of kidney fibrosis.

Kidney fibrosis is a common characteristic of chronic kidney disease and while the large conductance voltage and calcium-activated potassium channel (BK) is widely expressed in kidneys, its role in kidney fibrosis is unknown. To evaluate this, we found that BK protein expression was decreased in the fibrotic kidneys. Accompanying this was increased fibrotic marker protein expression of fibronectin, vimentin and α-smooth muscle actin and increased mRNA expressions of fibronectin, α-smooth muscle actin, collagen III and collagen I. These changes occurred in the unilateral ureteral obstruction and folic acid models of fibrosis and were more pronounced in BK knockout than in wild-type mice. Activation of BK activity by chemical NS1619 or BMS191011 channel openers attenuated kidney fibrosis in these two models while protecting kidney function in wild-type mice. BK deficiency up-regulated transforming growth factor-ß (TGF-ß)/transcription factor Smad2/3 signaling in the fibrotic kidney, whereas activation of BK activity inhibited this signaling pathway both in vivo and in vitro. BK channel activation increased the degradation of TGF-ß receptors induced by TGF-ß1 in vivo and in vitro. Furthermore, in cell lines HK-2, NRK49, and NRK-52E, BK channel activation by NS1619 led to increased caveolae formation and facilitated localization of TGF-ß receptors in the microdomains of lipid rafts. Thus, our data demonstrated that BK activation has an anti-fibrotic effect on kidney fibrosis by inhibiting the TGF-ß signaling pathway through accelerating TGF-ß receptor degradation via the caveolae route. Hence, our study provides innovative insight into BK as a potential therapeutic target for the treatment of kidney fibrosis.

Saikosaponin B2 attenuates kidney fibrosis via inhibiting the Hedgehog Pathway.

BACKGROUND: Renal interstitial fibrosis is a common pathway through which chronic kidney disease progresses to end-stage renal disease. There are currently no effective drugs available to treat kidney fibrosis, so traditional medicine is likely to be a candidate. The therapeutic potential of saikosaponin B2 (SSB2), a biologically active ingredient of Radix Bupleuri, on renal fibrosis has not been reported. METHODS: A unilateral ureteral obstruction (UUO) model was conducted to induce renal interstitial fibrosis in mice. SSB2's effect was valuated by histological staining and exploring the changes in expression of relative proteins and mRNAs. A conditional medium containing sonic hedgehog variant protein stimulating normal rat kidney interstitial fibroblast cells (NRK-49F) was used in an in vitro model to determine the possible mechanism. The molecular target of SSB2 was verified using several mutation plasmids. RESULTS: SSB2 administration reduced kidney injury and alleviated interstitial fibrosis by decreasing excessive accumulation of extracellular matrix components in UUO mice. It could also reduce the expression of α-SMA, fibronectin and Gli1, a crucial molecule of the hedgehog (Hh) signaling pathway both in vivo and in vitro. In NIH-3T3 cells simulated by conditional medium containing sonic hedgehog variant protein, SSB2 showed the ability to decrease the expression of Gli1 and Ptch1 mRNA. Using a dual-luciferase reporter assay, SSB2 suppressed the Gli-luciferase reporter activity in NIH-3T3 cells, and the IC50 was 0.49 µM, but had no effect on the TNF-α/NF-κB and Wnt/ß-catenin signaling pathways, indicating the inhibition selectivity on the Hh signaling pathway. Furthermore, SSB2 failed to inhibit the Hh pathway activity evoked by ectopic expression of Gli2ΔN and Smo D473H, suggesting that SSB2 might potentially act on smoothened receptors. CONCLUSION: SSB2 could attenuate renal fibrosis and decrease fibroblast activation by inhibiting the Hh signaling pathway.

Desensitizing Mitochondrial Permeability Transition by ERK-Cyclophilin D Axis Contributes to the Neuroprotective Effect of Gallic Acid against Cerebral Ischemia/Reperfusion Injury.

Ischemic stroke is a devastating disease with complex pathophysiology. Much evidence confirms that opening of the mitochondrial permeability transition pore (MPTP) is related with mitochondrial dysfunction to apoptosis in ischemic stroke, thus elucidating its signaling mechanism and screening novel MPTP inhibitor is therefore of paramount importance. Our earlier studies identified that gallic acid (GA), a naturally occurring plant phenol, endows with effect on inhibition of mitochondrial dysfunction, which has significant neuroprotective effect in cerebral ischemia/reperfusion injury. However, its molecular mechanisms regulating mitochondrial dysfunction remain elusive. Here, we uncover a role of GA in protecting mitochondria via MPTP inhibition. In addition to inhibit CypD binding to adenine nucleotide translocator, GA potentiates extracellular signal-regulated kinases (ERK) phosphorylation, leading to a decrease in cyclophilin D (CypD) expression, resulting in a desensitization to induction of MPTP, thus inhibiting caspase activation and ultimately giving rise to cellular survival. Our study firstly identifies ERK-CypD axis is one of the cornerstones of the cell death pathways following ischemic stroke, and confirms GA is a novel inhibitor of MPTP, which inhibits apoptosis depending on regulating the ERK-CypD axis.