Increased expression of desmin and vimentin reduces bladder smooth muscle contractility via JNK2

Dynamic phenotypic shifts and M2 receptor downregulation in bladder smooth muscle cells induced by mirabegron

Introduction

Mirabegron is available for treatment of overactive bladder (OAB). However, mechanisms underlying symptom improvements and long-term effects on bladder smooth muscle cells are uncertain. Contractility and growth of bladder smooth muscle contribute to OAB, and depend on smooth muscle phenotypes, and on muscarinic receptor expression. Here, we examined prolonged exposure to mirabegron (20-48 h) on phenotype markers, muscarinic receptor expression, and phenotype-dependent functions in human bladder smooth muscle cells (hBSMC).

Methods

Expression of markers for contractile (calponin, MYH11) and proliferative (MYH10, vimentin) phenotypes, proliferation (Ki-67), and of muscarinic receptors were assessed by RT-PCR. Proliferation, viability, actin organization and contractions in cultured hBSMC were examined by EdU, CCK-8, phalloidin staining and matrix contraction assays.

Results

Calponin-1 mRNA decreased with 100 nM and 150 nM mirabegron applied for 20 h (0.56-0.6 fold of controls). Decreases were resistant to the β3-AR antagonist L-748,337 (0.34-0.55 fold, 100-150 nM, 20 h). After 40 h, decreases occured in the presence of L-748,337, but not without L-748,337. MYH11 mRNA increased with 150 nM mirabegron (40 h, 1.9 fold). This was partly preserved with L-748,337, but not observed after 20 h mirabegron exposure. Vimentin mRNA reduced with 150 nM mirabegron after 20 h, but not after 40 h, with and without L-748,337 (0.71-0.63 fold). MYH10 mRNA expression remained unaffected by mirabegron. Exposure to 150 nM mirabegron increased Ki-67 mRNA after 20 h in the presence of, but not without L-748,337, and after 40 h without, but not with L-748,337. Proliferation rates and actin organization were stable with 50-150 nM mirabegron (24 h, 48 h). Viability increased significantly after mirabegron exposure for 20 h, and by trend after 40 h, which was fully sensitive to L-748,337. M2 mRNA was reduced by 20 h mirabegron, which was resistant to L-748,337. Carbachol (3 µM) enhanced time-dependent contractions of hBSMC, which was inhibited by mirabegron (150 nM) in late phases (24 h), but not in early phases of contractions. Conclusion: Mirabegron induces dynamic phenotype alterations and M2 downregulation in hBSMC, which is paralleled by time-shifted anticontractile effects. Phenotype transitions may be involved in improvements of storage symptoms in OAB by mirabegron.

The intricate cellular ecosystem of human peripheral veins as revealed by single-cell transcriptomic analysis

The venous system has been historically understudied despite its critical roles in blood distribution, heart function, and systemic immunity. This study dissects the microanatomy of upper arm veins at the single cell level, and how it relates to wall structure, remodeling processes, and inflammatory responses to injury. We applied single-cell RNA sequencing to 4 non-diseased human veins (3 basilic, 1 cephalic) obtained from organ donors, followed by bioinformatic and histological analyses. Unsupervised clustering of 20,006 cells revealed a complex ecosystem of endothelial cell (EC) types, smooth muscle cell (SMCs) and pericytes, various types of fibroblasts, and immune cell populations. The venous endothelium showed significant upregulation of cell adhesion genes, with arteriovenous zonation EC phenotypes highlighting the heterogeneity of vasa vasorum (VV) microvessels. Venous SMCs had atypical contractile phenotypes and showed widespread localization in the intima and media. MYH11+DESlo SMCs were transcriptionally associated with negative regulation of contraction and pro-inflammatory gene expression. MYH11+DEShi SMCs showed significant upregulation of extracellular matrix genes and pro-migratory mediators. Venous fibroblasts ranging from secretory to myofibroblastic phenotypes were 4X more abundant than SMCs and widely distributed throughout the wall. Fibroblast-derived angiopoietin-like factors were identified as versatile signaling hubs to regulate angiogenesis and SMC proliferation. An abundant monocyte/macrophage population was detected and confirmed by histology, including pro-inflammatory and homeostatic phenotypes, with cell counts positively correlated with age. Ligand-receptor interactome networks identified the venous endothelium in the main lumen and the VV as a niche for monocyte recruitment and infiltration. This study underscores the transcriptional uniqueness of venous cells and their relevance for vascular inflammation and remodeling processes. Findings from this study may be relevant for molecular investigations of upper arm veins used for vascular access creation, where single-cell analyses of cell composition and phenotypes are currently lacking.

Acute Exposure to Pyridostigmine Bromide Disrupts Cholinergic Myenteric Neuroimmune Function in Mice

Gulf War Illness (GWI) results from chemical exposure during the Gulf War, with notable impacts on gastrointestinal motility. Due to the limited demographic impacted by this ailment, an in-depth investigation of the GWI has yielded little regarding the underlying pathophysiological mechanisms. Here, the hypothesis that exposure to pyridostigmine bromide (PB) results in severe enteric neuro-inflammation, that cascades to disruptions in colonic motility, is tested. The analyses are performed on male C57BL/6 mice that are treated with physiologically similar doses of PB given to GW veterans. When colonic motility is assessed, GWI colons have significantly reduced forces in response to acetylcholine or electrical field stimulation. GWI is also accompanied by high levels of pro-inflammatory cytokines and chemokines, associated with increased numbers of CD40⁺ pro-inflammatory macrophages within the myenteric plexus. Enteric neurons responsible for mediating colonic motility reside within the myenteric plexus, and PB exposure reduced their numbers. Significant smooth muscle hypertrophy is also observed due to increased inflammation. Together, the results show that PB exposure caused functional and anatomical dysfunction, promoting impaired motility within the colon. Achieving a greater understanding of the mechanisms of GWI will allow more refinement in therapeutic options that improve veterans' quality of life.

Streptococcal autolysin promotes dysfunction of swine tracheal epithelium by interacting with vimentin

Streptococcus suis serotype 2 (SS2) is a major zoonotic pathogen resulting in manifestations as pneumonia and septic shock. The upper respiratory tract is typically thought to be the main colonization and entry site of SS2 in pigs, but the mechanism through which it penetrates the respiratory barrier is still unclear. In this study, a mutant with low invasive potential to swine tracheal epithelial cells (STECs) was screened from the TnYLB-1 transposon insertion mutant library of SS2, and the interrupted gene was identified as autolysin (atl). Compared to wild-type (WT) SS2, Δatl mutant exhibited lower ability to penetrate the tracheal epithelial barrier in a mouse model. Purified Atl also enhanced SS2 translocation across STEC monolayers in Transwell inserts. Furthermore, Atl redistributed the tight junctions (TJs) in STECs through myosin light chain kinase (MLCK) signaling, which led to increased barrier permeability. Using mass spectrometry, co-immunoprecipitation (co-IP), pull-down, bacterial two-hybrid and saturation binding experiments, we showed that Atl binds directly to vimentin. CRISPR/Cas9-targeted deletion of vimentin in STECs (VIM KO STECs) abrogated the capacity of SS2 to translocate across the monolayers, SS2-induced phosphorylation of myosin II regulatory light chain (MLC) and MLCK transcription, indicating that vimentin is indispensable for MLCK activation. Consistently, vimentin null mice were protected from SS2 infection and exhibited reduced tracheal and lung injury. Thus, MLCK-mediated epithelial barrier opening caused by the Atl-vimentin interaction is found to be likely the key mechanism by which SS2 penetrates the tracheal epithelium.

Streptococcus suis serotype 2 (SS2), an emerging zoonotic agent, can breach the respiratory barrier and cause invasive disease in pigs. Here, we identified the novel role of autolysin Atl in penetration of the respiratory barrier by SS2 and its systemic dissemination and identified its binding partner, vimentin, a type III intermediate filament protein. Atl contributed to the MLCK-triggered redistribution of tight junctions to open the tracheal epithelial barrier. Knockout of vimentin abolished the ability of SS2 to penetrate the monolayer barrier and the activation of MLCK. Furthermore, vimentin null mice were protected from infection by intranasally administered SS2. This study is the first to demonstrate that the interaction between the GBS Bsp-like domain of Atl and vimentin promotes MLCK-mediated dysfunction of the epithelial barrier, which may provide theoretical information for prophylactic and/or therapeutic treatments against diseases caused by similar respiratory pathogens.

Cytoskeleton and Associated Proteins: Pleiotropic JNK Substrates and Regulators

This review extensively reports data from the literature concerning the complex relationships between the stress-induced c-Jun N-terminal kinases (JNKs) and the four main cytoskeleton elements, which are actin filaments, microtubules, intermediate filaments, and septins. To a lesser extent, we also focused on the two membrane-associated cytoskeletons spectrin and ESCRT-III. We gather the mechanisms controlling cytoskeleton-associated JNK activation and the known cytoskeleton-related substrates directly phosphorylated by JNK. We also point out specific locations of the JNK upstream regulators at cytoskeletal components. We finally compile available techniques and tools that could allow a better characterization of the interplay between the different types of cytoskeleton filaments upon JNK-mediated stress and during development. This overview may bring new important information for applied medical research.