Transforming growth factor-β1 (TGF-β1) regulates cell junction restructuring via Smad-mediated repression and clathrin-mediated endocytosis of nectin-like molecule 2 (Necl-2)

Lactoferrin Restores the Deoxynivalenol-Impaired Spermatogenesis and Blood-Testis Barrier Integrity via Improving the Antioxidant Capacity and Modifying the Cell Adhesion and Inflammatory Response

Deoxynivalenol (DON) is among the most prevalent contaminants in cereal crops and has been demonstrated to impair male spermatogenesis and induce oxidative stress, testicular apoptosis, and disruption of the blood-testis barrier (BTB). Lactoferrin (LF) is an iron-binding glycoprotein with multifunctions including anti-inflammation and antioxidation. Thus, this study aimed to investigate the effects of LF on the spermatogenesis and integrity of the BTB in DON-exposed mice. Thirty-two male mice were allotted to four groups for a 35-day feeding period: vehicle (basal diet), DON (12 mg/kg), LF (10 mg/d, p.o.), and DON + LF. The results showed that DON induced vacuolization of the spermatogenic epithelium, broke the adhesion junction between Sertoli cells and spermatids established by N-cadherin and induced testicular oxidative stress. LF administration restored sperm production, attenuated the DON-induced oxidative stress and reduced the breakages in adhesion junction. DON exposure enhanced the protein expression of occludin. Transcriptional profiling of the testis observed a disturbance in the expression profiles of cell adhesion and inflammatory response genes, and LF administration reversed these gene expressions. Furthermore, down-regulated signaling pathways, including the apical junction, TNFα signaling via NF-κB, and TGF-β in the DON group were observed. These were restored by LF. Enrichment analysis between DON + LF group and vehicle also confirmed the absence of these pathways. These findings indicated that LF eliminated the DON-induced detriment to spermatogenesis and cell connections between Sertoli cells and spermatids via improving antioxidant capacity and modifying the inflammatory response and cell adhesion genes.

Short Disordered Epitope of CRTAM Ig-Like V Domain as a Potential Target for Blocking Antibodies

Class-I Restricted T Cell-Associated Molecule (CRTAM) is a protein that is expressed after T cell activation. The interaction of CRTAM with its ligand, nectin-like 2 (Necl2), is required for the efficient production of IL-17, IL-22, and IFNγ by murine CD4 T cells, and it plays a role in optimal CD8 T and NK cell cytotoxicity. CRTAM promotes the pro-inflammatory cytokine profile; therefore, it may take part in the immunopathology of autoimmune diseases such as diabetes type 1 or colitis. Thus, antibodies that block the interaction between CRTAM and Necl2 would be useful for controlling the production of these inflammatory cytokines. In this work, using bioinformatics predictions, we identified three short disordered epitopes (sDE1-3) that are located in the Ig-like domains of murine CRTAM and are conserved in mammalian species. We performed a structural analysis by molecular dynamics simulations of sDE1 (QHPALKSSKY, Ig-like V), sDE2 (QRNGEKSVVK, Ig-like C1), and sDE3 (CSTERSKKPPPQI, Ig-like C1). sDE1, which is located within a loop of the contact interface of the heterotypic interaction with Nectl2, undergoes an order–disorder transition. On the contrary, even though sDE2 and sDE3 are flexible and also located within loops, they do not undergo order–disorder transitions. We evaluated the immunogenicity of sDE1 and sDE3 through the expression of these epitopes in chimeric L1 virus-like particles. We confirmed that sDE1 induces polyclonal antibodies that recognize the native folding of CRTAM expressed in activated murine CD4 T cells. In contrast, sDE3 induces polyclonal antibodies that recognize the recombinant protein hCRTAM-Fc, but not the native CRTAM. Thus, in this study, an exposed disordered epitope in the Ig-like V domain of CRTAM was identified as a potential site for therapeutic antibodies.

Transforming growth factor-β3 regulates cell junction restructuring via MAPK-mediated mRNA destabilization and Smad-dependent protein degradation of junctional adhesion molecule B (JAM-B)

Junctional adhesion molecule-B (JAM-B) is found between Sertoli cells at the blood-testis barrier (BTB) as well as between Sertoli and germ cells at the apical ectoplasmic specializations (ES) in the testis. The expression of JAM-B is tightly regulated to modulate the passage of spermatocytes across the BTB as well as the release of mature spermatozoa from the seminiferous epithelium. Transforming growth factor beta (TGF-β) family is implicated in the regulation of testicular cell junction dynamics during spermatogenesis. This study aims to investigate the effects of TGF-β3 on the expression of JAM-B as well as the underlying mechanisms on how TGF-β3 regulates JAM-B expression to facilitate the disassembly of the BTB and apical ES. Our results revealed that TGF-β3 suppresses JAM-B at post-transcriptional and post-translational levels. Inhibitor, siRNA knockdown and co-immunoprecipitation have shown that TGF-β3 induces JAM-B protein degradation via ubiquitin-proteasome pathway. Immunofluorescence staining further confirmed that blockage of ubiquitin-proteasome pathway could abrogate TGF-β3-induced loss of JAM-B at the cell-cell interface. siRNA knockdown and immunofluorescence staining also demonstrated that activation of Smad signaling is required for TGF-β3-induced JAM-B protein degradation. In addition, TGF-β3 reduces JAM-B mRNA levels, at least in part, via post-transcriptional regulation. mRNA stability assay has confirmed that TGF-β3 promotes the degradation of JAM-B transcript and TGF-β3-mediated mRNA destabilization requires the activation of ERK1/2 and p54 JNK signal cascades. Taken together, TGF-β3 significantly downregulates JAM-B expression via post-transcriptional and post-translational modulation and results in the disruption of BTB and apical ES.

Roles of TGF-β/Smad signaling pathway in pathogenesis and development of gluteal muscle contracture

PURPOSE OF THE STUDY

Gluteal muscle contracture (GMC) is a chronic fibrotic disease of gluteal muscles which is characterized by excessive deposition of collagen in the extracellular matrix. Transforming growth factor (TGF)-βs have been shown to play an important role in the progression of GMC. However, the underlying mechanisms are not entirely clear. We sought to explore the expression of TGF-β/Smad pathway proteins and their downstream targets in gluteal muscle contracture disease.

MATERIALS AND METHODS

The expression levels of collagens type I/III, TGF-β1, Smad2/3/4/7 and PAI-1 (plasminogen activator inhibitor type 1) in gluteal muscle contraction (GMC) patients were measured using immunohistochemistry, reverse transcription and polymerase chain reaction (RT-PCR) and western blot assays.

RESULTS

The expressions of collagens type I/III and TGF-β1 were significantly increased in the contraction band compared with unaffected muscle. In addition, R-Smad phosphorylation and Smad4 protein expression in the contraction band were also elevated, while the expression of Smad7 was significantly decreased in the fibrotic muscle of the GMC patients compared to the unaffected adjacent muscle. The protein and mRNA levels of PAI-1 were also remarkably increased in the contraction band compared with adjacent muscle. Immunohistochemical analysis also demonstrated that the expression levels of TGF-β1 and PAI-1 were higher in contraction band than those in the adjacent muscle.

CONCLUSION

Our data confirm the stimulating effects of the TGF-β/Smad pathway in gluteal muscle contracture disease and reveal the internal changes of TGF-β/Smad pathway proteins and their corresponding targets in gluteal muscle contracture patients.

Synergistic effect of interferon-gamma and tumor necrosis factor-alpha on coxsackievirus and adenovirus receptor expression: an explanation of cell sloughing during testicular inflammation in mice

Coxsackievirus and adenovirus receptor (CAR) is a junction molecule that expresses on Sertoli and germ cells. It mediates Sertoli-germ cell adhesion and facilitates migration of preleptotene/leptotene spermatocytes across the blood-testis barrier, suggesting that CAR-based cell adhesion and migration are crucial for spermatogenesis. Interferon-gamma (IFNG) and tumor necrosis factor alpha (TNF) are two major cytokines that are elevated during testicular inflammation and cause reduced fertility. We investigated the mechanism by which IFNG and TNF exert their disruptive effects on testicular cell adhesion. We have demonstrated that combined treatment with IFNG and TNF (IFNG+TNF) exerts a synergistic effect by downregulating CAR mRNA and protein levels. Immunofluorescence staining revealed that IFNG+TNF treatment effectively removes CAR from the site of cell-cell contact. Using inhibitor and co-immunoprecipitation, we confirmed that IFNG+TNF mediates CAR protein degradation via ubiquitin-proteasome and NFKB pathways. Blockage of ubiquitin-proteasome pathway significantly inhibits CAR degradation, as indicated by the reappearance of CAR at the site of cell-cell contact. Additionally, IFNG+TNF reduces CAR mRNA via transcriptional regulation. Mutational studies have shown that IFNG+TNF-induced CAR repression is achieved by suppression of the basal transcription. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays further confirmed that IFNG+TNF treament not only inhibits binding of the basal transcription factors but also promotes binding of NFKB subunits and Sp1 (negative regulators) to the CAR promoter region. Taken together, IFNG+TNF treatment significantly downregulates CAR expression, which provides an explanation of how cell sloughing in the epithelium mediates, by loss of CAR-based cell adhesion, during testicular inflammation.