Gap junctions amplify TRPV4 activation-initiated cell injury via modification of intracellular Ca2+ and Ca2+-dependent regulation of TXNIP

Calcium influx through TRPV4 channels involve in hyperosmotic stress-induced epithelial-mesenchymal transition in tubular epithelial cells

The epithelial-mesenchymal transition (EMT) is a biological process that occurs in the pathogenesis of kidney diseases in which injured tubular epithelial cells transform into myofibroblasts. We previously showed that mannitol-mediated hyperosmotic stress induces EMT of tubular epithelial cells. Although Ca²⁺ signaling is essential for the induction of EMT in tubular epithelial cells, the role of specific calcium channels is unknown. In this study, we assessed the transient receptor potential vanilloid 4 (TRPV4)-mediated Ca²⁺ influx in the hyperosmolarity-induced EMT. The Fluo-4 assay was used to examine the effect of hyperosmotic stress on the intracellular Ca²⁺ level of normal rat kidney (NRK)-52E cells. Expression of a mesenchymal marker α-smooth muscle actin (α-SMA) and an epithelial marker E-cadherin was also observed by fluorescence microscopy. The hyperosmotic stress caused a transient increase in intracellular Ca²⁺ concentration as well as a decrease in E-cadherin and an increase in α-SMA expressions in tubular epithelial cells, indicating the induction of EMT. A TRPV4 channel antagonist inhibited hyperosmotic stress-induced Ca²⁺ influx and the EMT, whereas, a TRPV4 channel agonist increased Ca²⁺ influx and EMT induction in tubular epithelial cells without the hyperosmotic stress. These findings suggest that Ca²⁺ influx through TRPV4 channels contributes to the hyperosmotic stress-induced EMT of tubular epithelial cells.

Polarization of rheumatoid macrophages is regulated by the CDKN2B-AS1/ MIR497/TXNIP axis

The polarization of macrophages plays a critical role in the pathophysiology of rheumatoid arthritis. The macrophages can have pro-inflammatory M1 polarization and various types of alternative anti-inflammatory M2 polarization. Our preliminary results showed that the CDKN2B-AS1/MIR497/TXNIP axis might regulate macrophages of rheumatoid arthritis patients. Therefore, we hypothesized that this axis regulated the polarization of rheumatoid macrophages. Flow cytometry was used to determine the surface polarization markers in M1 or M2 macrophages from healthy donors and rheumatoid arthritis patients. The QPCR and Western Blotting were used to compare the expression of the CDKN2B-AS1/MIR497/TXNIP axis in these macrophages. We Knocked down and overexpressed the axis in the macrophage cell line MD to test its roles in macrophage polarization. Compared to cells from healthy donors, cells from rheumatoid arthritis patients expressed higher levels of CD40 and CD80 and lower levels of CD16, CD163, CD206, and CD200R after polarization, they also expressed higher CDKN2B-AS1, lower MIR497, and higher TXNIP. In macrophages from healthy donors, there was no correlation among CDKN2B-AS1, MIR497, and TXNIP. But in macrophages from patients, there were significant correlations. The CDKN2B-AS1 knockdown, MIR497 mimics suppressed the M1 polarization but promoted the M2 polarization in MD cells, while the MIR497 knockdown and the TXNIP overexpression did the opposite. This study demonstrated that elevated CDKN2B-AS1 in macrophages promotes the M1 polarization and inhibited the M2 polarization of macrophages by the CDKN2B-AS1/ MIR497/TXNIP axis.