Tight junction protein claudin‐1 is downregulated by TGF‐β1 via MEK signaling in benign prostatic epithelial cells

Abstract

Background Benign prostatic hyperplasia (BPH) is arguably the most common disease in aging men. Although the etiology is not well understood, chronic prostatic inflammation is thought to play an important role in BPH initiation and progression. Our recent studies suggest that the prostatic epithelial barrier is compromised in glandular BPH tissues. The proinflammatory cytokine transforming growth factor beta 1 (TGF‐β1) impacts tight junction formation, enhances epithelial barrier permeability, and suppresses claudin‐1 messenger RNA expression in prostatic epithelial cells. However, the role of claudin‐1 in the prostatic epithelial barrier and its regulation by TGF‐β1 in prostatic epithelial cells are not clear. Methods The expression of claudin‐1 was analyzed in 22 clinical BPH specimens by immunohistochemistry. Human benign prostate epithelial cell lines BPH‐1 and BHPrE1 were treated with TGF‐β1 and transfected with small interfering RNAs specific to claudin‐1. Epithelial monolayer permeability changes in the treated cells were measured using trans‐epithelial electrical resistance (TEER). The expression of claudin‐1, E‐cadherin, N‐cadherin, snail, slug, and activation of mitogen‐activated proteins kinases (MAPKs) and AKT was assessed following TGF‐β1 treatment using Western blot analysis. Results Claudin‐1 expression was decreased in glandular BPH tissue compared with adjacent normal prostatic tissue in patient specimens. TGF‐β1 treatment or claudin‐1 knockdown in prostatic epithelial cell lines increased monolayer permeability. TGF‐β1 decreased levels of claudin‐1 and increased levels of snail and slug as well as increased phosphorylation of the MAPK extracellular signal‐regulated kinase‐1/2 (ERK‐1/2) in both BPH‐1 and BHPrE1 cells. Overexpression of snail or slug had no effect on claudin‐1 expression. In contrast, PD98059 and U0126, inhibitors of the upstream activator of ERK‐1/2 (ie, MEK‐1/2) restored claudin‐1 expression level as well as the epithelial barrier. Conclusion Our findings suggest that downregulation of claudin‐1 by TGF‐β1 acting through the noncanonical MEK‐1/2/ERK‐1/2 pathway triggers increased prostatic epithelial monolayer permeability in vitro. These findings also suggest that elevated TGF‐β1 may contribute to claudin‐1 downregulation and compromised epithelial barrier in clinical BPH specimens.

A Comprehensive Analysis of Metabolomics and Transcriptomics Reveals Novel Biomarkers and Mechanistic Insights on Lorlatinib Crosses the Blood-Brain Barrier

“…OPN plays an essential role in tight junctions by affecting occluding via a well-defined pathway ( Woo et al, 2019 ). There are also elusive underlying mechanisms regarding OPN’s regulation of ZO-1, claudin-5 ( Zhang et al, 2018 ) and of TGF‐βmodulating claudin ( Wang et al, 2020 ). The variation in response of claudin-5 at different time periods is probably due to the influence of requiring multiple signal pathway transmissions, which maybe also be the major reason for a feedback increase of VEGF at the initial time period after lorlatinib administration.…”

RNA sequencing and integrative analysis reveal pathways and hub genes associated with TGFβ1 stimulation on prostatic stromal cells

“…The stromal cells were used at passages 3-5. According to the previous literature, the commonly used dose of TGFβ1 in the study of benign prostatic hyperplasia ranges from 1 ng/ml to 10 ng/ml (Sheng et al, 2018;Wang et al, 2020;. Therefore, cells in our study were treated with 10 ng/ml TGFβ1 (R&D Systems, MN, United States) for 72 h.…”

“…The transforming growth factor beta (TGFβ) family plays an important role in the proliferation and differentiation of BPH stroma, as well as being a key factor for androgencontrolled prostate growth (Schauer and Rowley, 2011;De Nunzio et al, 2016). The upregulation of TGF-β1 (which is produced by prostatic stromal cells) during BPH would facilitate expansion of the stromal compartment, epithelial to mesenchymal transition, down-regulation of claudin-1, and epithelial barrier damage (Schauer and Rowley, 2011;De Nunzio et al, 2016;Wang et al, 2020;Chen et al, 2021). Moreover, TGFβ1 is one of the critical cytokines that induce fibroblasts to transform into myofibroblasts and promotes fibrosis, during which the expression of COL1A1, COL3A1, and α-SMA is increased (Sheng et al, 2018;Wang et al, 2019).…”

“…Moreover, TGFβ1 is one of the critical cytokines that induce fibroblasts to transform into myofibroblasts and promotes fibrosis, during which the expression of COL1A1, COL3A1, and α-SMA is increased (Sheng et al, 2018;Wang et al, 2019). The TGFβ1 expression is increased with age in the prostate (Wang et al, 2020), and the overexpression of TGF-β1 in the murine prostate induces inflammation and fibrosis (Barron et al, 2010). Although TGFβ1 can promote proliferation and fibrosis of prostatic stromal cells, it is not very clear which important pathways and key genes are the possible downstream of TGFβ1.…”

MicroRNA‐21‐5p functions via RECK/MMP9 as a proalgesic regulator of the blood nerve barrier in nerve injury

“…MMPs, such as MMP9, contribute to both the initiation of neuropathic pain and barrier disruption via regulating claudins 14,15 . Moreover, miR‐21 positively regulates transforming growth factor beta (TGF‐β), an anti‐inflammatory cytokine also involved in barrier impairment 16,17 …”