Skeletal Muscle Mitochondrial Dysfunction Mediated by Pseudomonas aeruginosa Quorum Sensing Transcription Factor MvfR: Reversing Effects with Anti-MvfR and Mitochondrial-Targeted Compounds.

Sepsis and chronic infections with Pseudomonas aeruginosa, a leading "ESKAPE" bacterial pathogen, are associated with increased morbidity and mortality and skeletal muscle atrophy. The actions of this pathogen on skeletal muscle remain poorly understood. In skeletal muscle, mitochondria serve as a crucial energy source, which may be perturbed by infection. Here, using the well-established backburn and infection model of murine P. aeruginosa infection, we deciphered the systemic impact of the quorum sensing (QS) transcription factor MvfR by interrogating five days post-infection its effect on mitochondrial-related functions in the gastrocnemius skeletal muscle and the outcome of the pharmacological inhibition of MvfR function and that of the mitochondrial-targeted peptide, Szeto-Schiller 31 (SS-31). Our findings show that the MvfR perturbs ATP generation, oxidative phosphorylation (OXPHOS), and antioxidant response, elevates the production of reactive oxygen species, and promotes oxidative damage of mitochondrial DNA in the gastrocnemius muscle of infected mice. These impairments in mitochondrial-related functions were corroborated by the alteration of key mitochondrial proteins involved in electron transport, mitochondrial biogenesis, dynamics and quality control, and mitochondrial uncoupling. Pharmacological inhibition of MvfR using the potent anti-MvfR lead, D88, we developed, or the mitochondrial-targeted peptide SS-31 rescued the MvfR- mediated alterations observed in mice infected with the wild-type strain PA14. Our study provides insights into the actions of MvfR in orchestrating mitochondrial dysfunction in the skeletal murine muscle, and it presents novel therapeutic approaches for optimizing clinical outcomes in affected patients.

Skeletal muscle mitochondrial dysfunction mediated by Pseudomonas aeruginosa quorum-sensing transcription factor MvfR: reversing effects with anti-MvfR and mitochondrial-targeted compounds.

Sepsis and chronic infections with Pseudomonas aeruginosa, a leading "ESKAPE" bacterial pathogen, are associated with increased morbidity and mortality and skeletal muscle atrophy. The actions of this pathogen on skeletal muscle remain poorly understood. In skeletal muscle, mitochondria serve as a crucial energy source, which may be perturbed by infection. Here, using the well-established backburn and infection model of murine P. aeruginosa infection, we deciphered the systemic impact of the quorum-sensing transcription factor MvfR (multiple virulence factor regulator) by interrogating, 5 days post-infection, its effect on mitochondrial-related functions in the gastrocnemius skeletal muscle and the outcome of the pharmacological inhibition of MvfR function and that of the mitochondrial-targeted peptide, Szeto-Schiller 31 (SS-31). Our findings show that the MvfR perturbs adenosine triphosphate generation, oxidative phosphorylation, and antioxidant response, elevates the production of reactive oxygen species, and promotes oxidative damage of mitochondrial DNA in the gastrocnemius muscle of infected mice. These impairments in mitochondrial-related functions were corroborated by the alteration of key mitochondrial proteins involved in electron transport, mitochondrial biogenesis, dynamics and quality control, and mitochondrial uncoupling. Pharmacological inhibition of MvfR using the potent anti-MvfR lead, D88, we developed, or the mitochondrial-targeted peptide SS-31 rescued the MvfR-mediated alterations observed in mice infected with the wild-type strain PA14. Our study provides insights into the actions of MvfR in orchestrating mitochondrial dysfunction in the skeletal murine muscle, and it presents novel therapeutic approaches for optimizing clinical outcomes in affected patients. IMPORTANCE: Skeletal muscle, pivotal for many functions in the human body, including breathing and protecting internal organs, contains abundant mitochondria essential for maintaining cellular homeostasis during infection. The effect of Pseudomonas aeruginosa (PA) infections on skeletal muscle remains poorly understood. Our study delves into the role of a central quorum-sensing transcription factor, multiple virulence factor regulator (MvfR), that controls the expression of multiple acute and chronic virulence functions that contribute to the pathogenicity of PA. The significance of our study lies in the role of MvfR in the metabolic perturbances linked to mitochondrial functions in skeletal muscle and the effectiveness of the novel MvfR inhibitor and the mitochondrial-targeted peptide SS-31 in alleviating the mitochondrial disturbances caused by PA in skeletal muscle. Inhibiting MvfR or interfering with its effects can be a potential therapeutic strategy to curb PA virulence.

A Novel Microphysiological Colon Platform to Decipher Mechanisms Driving Human Intestinal Permeability.

BACKGROUND & AIMS: The limited availability of organoid systems that mimic the molecular signatures and architecture of human intestinal epithelium has been an impediment to allowing them to be harnessed for the development of therapeutics as well as physiological insights. We developed a microphysiological Organ-on-Chip (Emulate, Inc, Boston, MA) platform designed to mimic properties of human intestinal epithelium leading to insights into barrier integrity. METHODS: We combined the human biopsy-derived leucine-rich repeat-containing G-protein-coupled receptor 5-positive organoids and Organ-on-Chip technologies to establish a micro-engineered human Colon Intestine-Chip (Emulate, Inc, Boston, MA). We characterized the proximity of the model to human tissue and organoids maintained in suspension by RNA sequencing analysis, and their differentiation to intestinal epithelial cells on the Colon Intestine-Chip under variable conditions. Furthermore, organoids from different donors were evaluated to understand variability in the system. Our system was applied to understanding the epithelial barrier and characterizing mechanisms driving the cytokine-induced barrier disruption. RESULTS: Our data highlight the importance of the endothelium and the in vivo tissue-relevant dynamic microenvironment in the Colon Intestine-Chip in the establishment of a tight monolayer of differentiated, polarized, organoid-derived intestinal epithelial cells. We confirmed the effect of interferon-γ on the colonic barrier and identified reorganization of apical junctional complexes, and induction of apoptosis in the intestinal epithelial cells as mediating mechanisms. We show that in the human Colon Intestine-Chip exposure to interleukin 22 induces disruption of the barrier, unlike its described protective role in experimental colitis in mice. CONCLUSIONS: We developed a human Colon Intestine-Chip platform and showed its value in the characterization of the mechanism of action of interleukin 22 in the human epithelial barrier. This system can be used to elucidate, in a time- and challenge-dependent manner, the mechanism driving the development of leaky gut in human beings and to identify associated biomarkers.

B-type natriuretic peptide is upregulated by c-Jun N-terminal kinase and contributes to septic hypotension.

B-type natriuretic peptide (BNP) is secreted by ventricular cardiomyocytes in response to various types of cardiac stress and has been used as a heart failure marker. In septic patients, increased BNP suggests poor prognosis; however, no causal link has been established. Among various effects, BNP decreases systemic vascular resistance and increases natriuresis that leads to lower blood pressure. We previously observed that JNK inhibition corrects cardiac dysfunction and suppresses cardiac BNP mRNA in endotoxemia. In this study, we investigated the transcriptional mechanism that regulates BNP expression and the involvement of plasma BNP in causing septic hypotension. Our in vitro and in vivo findings confirmed that activation of JNK signaling increases BNP expression in sepsis via direct binding of c-Jun in activating protein-1 (AP-1) regulatory elements of the Nppb promoter. Accordingly, genetic ablation of BNP, as well as treatment with a potentially novel neutralizing anti-BNP monoclonal antibody (19B3) or suppression of its expression via administration of JNK inhibitor SP600125 improved cardiac output, stabilized blood pressure, and improved survival in mice with polymicrobial sepsis. Therefore, inhibition of JNK signaling or BNP in sepsis appears to stabilize blood pressure and improve survival.

Activin A forms a non-signaling complex with ACVR1 and type II Activin/BMP receptors via its finger 2 tip loop.

Activin A functions in BMP signaling in two ways: it either engages ACVR1B to activate Smad2/3 signaling or binds ACVR1 to form a non-signaling complex (NSC). Although the former property has been studied extensively, the roles of the NSC remain unexplored. The genetic disorder fibrodysplasia ossificans progressiva (FOP) provides a unique window into ACVR1/Activin A signaling because in that disease Activin can either signal through FOP-mutant ACVR1 or form NSCs with wild-type ACVR1. To explore the role of the NSC, we generated 'agonist-only' Activin A muteins that activate ACVR1B but cannot form the NSC with ACVR1. Using one of these muteins, we demonstrate that failure to form the NSC in FOP results in more severe disease pathology. These results provide the first evidence for a biological role for the NSC in vivo and pave the way for further exploration of the NSC's physiological role in corresponding knock-in mice.

Cobalt(II) complexes with the non-steroidal anti-inflammatory drug diclofenac and nitrogen-donor ligands.

The interaction of the non-steroidal anti-inflammatory drug sodium diclofenac with CoCl2 in the absence or presence of the nitrogen-donor ligands 2,2'-bipyridine, 1,10-phenanthroline, 2,2'-bipyridylamine, pyridine or imidazole resulted in the formation of six mononuclear Co(II) complexes. The complexes were characterized by diverse physicochemical and spectroscopic techniques and single-crystal X-ray crystallography revealing a monodentate or a bidentate chelating binding mode of the diclofenac ligands. The scavenging activity of the complexes was evaluated in vitro against the free radicals of 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl; the complexes present significant scavenging activity of ABTS and hydroxyl radicals. The interaction of the complexes with calf-thymus (CT) DNA and bovine serum albumin (BSA) was also investigated; the complexes can bind tightly to CT DNA via intercalation and can bind to BSA tightly and reversibly.