LncRNA SNHG8 upregulates MUC5B to induce idiopathic pulmonary fibrosis progression by targeting miR-4701-5p

Long noncoding RNAs (lncRNAs) play a critical role in idiopathic pulmonary fibrosis (IPF); however, the underlying molecular mechanisms are unclear. Our study demonstrated that lncRNA small nucleolar RNA host gene 8 (SNHG8) was increased in bleomycin (BLM)-induced A549 cells. LncRNA SNHG8 overexpression further elevated fibrosis-related factors monocyte chemotactic protein 1 (MCP1), CC motif chemokine ligand 18 (CCL18), and α-smooth muscle actin (α-SMA), as well as increased collagen type I alpha-1 chain (COL1A1) and collagen type III alpha-1 chain (COL3A1). Meanwhile, lncRNA SNHG8 knockdown exhibited an opposite role in reducing BLM-induced pulmonary fibrosis. With regard to the mechanism, SNHG8 was then revealed to act as a competing endogenous RNA (ceRNA) for microRNA (miR)-4701-5p in regulating Mucin 5B (MUC5B) expression. Furthermore, the interactions between SNHG8 and miR-4701-5p, between miR-4701-5p and MUC5B, and between SNHG8 and MUC5B on the influence of fibrosis-related indicators were confirmed, respectively. In addition, SNHG8 overexpression enhanced the levels of transforming growth factor (TGF)-β1 and phosphorylation Smad2/3 (p-Smad2/3), which was suppressed by SNHG8 knockdown in BLM-induced A549 cells. Moreover, miR-4701-5p inhibitor-induced elevation of TGF-β1 and p-Smad2/3 was significantly suppressed by SNHG8 knockdown. In conclusion, SNHG8 knockdown attenuated pulmonary fibrosis progression by regulating miR-4701-5p/MUC5B axis, which might be associated with the modulation of TGF-β1/Smad2/3 signaling. These findings reveal that lncRNA SNHG8 may become a potential target for the treatment of IPF.

Biochanin A alleviates unilateral ureteral obstruction-induced renal interstitial fibrosis and inflammation by inhibiting the TGF-β1/Smad2/3 and NF-kB/NLRP3 signaling axis in mice

AIMS

Tubulointerstitial fibrosis, a frequent complication of chronic kidney disease (CKD) is a major public health issue. Biochanin A (BCA), an isoflavone, has numerous pharmacological activities. However, its effect on renal fibrosis and underlying molecular mechanism has not yet been clarified. This study explored the effect of BCA on renal tubulointerstitial fibrosis and inflammation in mice.

MAIN METHODS

The mouse model of unilateral ureteral obstruction (UUO) in vivo and transforming growth factor (TGF)-β1 activated renal fibroblast (NRK 49F) cells in vitro model were used to assess the antifibrotic effect of BCA. Biochemical analysis, histopathology, western blotting, and immunofluorescent staining methods were performed to elucidate the mechanism of BCA.

KEY FINDINGS

In vitro, BCA suppressed the expression of fibrogenic proteins in TGF-β1-activated renal fibroblasts. The treatment with BCA displayed less tubular injury, prevented the aberrant accumulation of extracellular matrix (ECM) components, and inhibited the TGF-β1/Smad2/3 signaling axis in the kidneys. Furthermore, BCA impeded the phosphorylation of NF-kB(p65) and blunted the expression of inflammatory genes in the obstructed kidneys. The UUO induced expressions of nod-like receptor protein 3 (NLRP3), active caspase 1, interleukin(IL)-18, and IL-1β proteins were decreased in the BCA treated groups. We also found the increased expression of redox-sensitive nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) proteins in BCA treated groups compared to the UUO control.

SIGNIFICANCE

These findings indicate that BCA has a therapeutic benefit against renal fibrosis, and the ameliorative effect is mediated via inhibiting the TGF-β1/Smad2/3 and NF-kB/NLRP3 signaling axis.

Activation of TRPV4 by dietary apigenin antagonizes renal fibrosis in deoxycorticosterone acetate (DOCA)-salt-induced hypertension

Hypertension-induced renal fibrosis contributes to the progression of chronic kidney disease, and apigenin, an anti-hypertensive flavone that is abundant in celery, acts as an agonist of transient receptor potential vanilloid 4 (TRPV4). However, whether apigenin reduces hypertension-induced renal fibrosis, as well as the underlying mechanism, remains elusive. In the present study, the deoxycorticosterone acetate (DOCA)-salt hypertension model was established in male Sprague-Dawley rats that were treated with apigenin or vehicle for 4 weeks. Apigenin significantly attenuated the DOCA-salt-induced structural and functional damage to the kidney, which was accompanied by reduced expression of transforming growth factor-β1 (TGF-β1)/Smad2/3 signaling pathway and extracellular matrix proteins. Immunochemistry, cell-attached patch clamp and fluorescent Ca²⁺ imaging results indicated that TRPV4 was expressed and activated by apigenin in both the kidney and renal cells. Importantly, knockout of TRPV4 in mice abolished the beneficial effects of apigenin that were observed in the DOCA-salt hypertensive rats. Additionally, apigenin directly inhibited activation of the TGF-β1/Smad2/3 signaling pathway in different renal tissues through activation of TRPV4 regardless of the type of pro-fibrotic stimulus. Moreover, the TRPV4-mediated intracellular Ca²⁺ influx activated the AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) pathway, which inhibited the TGF-β1/Smad2/3 signaling pathway. In summary, dietary apigenin has beneficial effects on hypertension-induced renal fibrosis through the TRPV4-mediated activation of AMPK/SIRT1 and inhibition of the TGF-β1/Smad2/3 signaling pathway. This work suggests that dietary apigenin may represent a promising lifestyle modification for the prevention of hypertension-induced renal damage in populations that consume a high-sodium diet.