Genetic deletion of TNFR2 augments inflammatory response and blunts satellite-cell-mediated recovery response in a hind limb ischemia model

The ability of microRNAs to regulate the immune response in ischemia/reperfusion inflammatory pathways

MicroRNAs play a crucial role in regulating the immune responses induced by ischemia/reperfusion injury. Through their ability to modulate gene expression, microRNAs adjust immune responses by targeting specific genes and signaling pathways. This review focuses on the impact of microRNAs on the inflammatory pathways triggered during ischemia/reperfusion injury and highlights their ability to modulate inflammation, playing a critical role in the pathophysiology of ischemia/reperfusion injury. Dysregulated expression of microRNAs contributes to the pathogenesis of ischemia/reperfusion injury, therefore targeting specific microRNAs offers an opportunity to restore immune homeostasis and improve patient outcomes. Understanding the complex network of immunoregulatory microRNAs could provide novel therapeutic interventions aimed at attenuating excessive inflammation and preserving tissue integrity.

TFNR2 in Ischemia-Reperfusion Injury, Rejection, and Tolerance in Transplantation

Tumor necrosis factor receptor 2 (TNFR2) has been shown to play a crucial role in CD4+ T regulatory cells (CD4+Tregs) expansion and suppressive function. Increasing evidence has also demonstrated its role in a variety of immune regulatory cell subtypes such as CD8+ T regulatory cells (CD8+ Tregs), B regulatory cells (Bregs), and myeloid-derived suppressor cells (MDSCs). In solid organ transplantation, regulatory immune cells have been associated with decreased ischemia-reperfusion injury (IRI), improved graft survival, and improved overall outcomes. However, despite TNFR2 being studied in the context of autoimmune diseases, cancer, and hematopoietic stem cell transplantation, there remains paucity of data in the context of solid organ transplantation and islet cell transplantation. Interestingly, TNFR2 signaling has found a clinical application in islet transplantation which could guide its wider use. This article reviews the current literature on TNFR2 expression in immune modulatory cells as well as IRI, cell, and solid organ transplantation. Our results highlighted the positive impact of TNFR2 signaling especially in kidney and islet transplantation. However, further investigation of TNFR2 in all types of solid organ transplantation are required as well as dedicated studies on its therapeutic use during induction therapy or treatment of rejection.

Cytokine Signaling in Skeletal Muscle Wasting

Skeletal muscle wasting occurs in a variety of diseases including diabetes, cancer, Crohn's disease, chronic obstructive pulmonary disease (COPD), disuse, and denervation. Tumor necrosis factor α (TNF-α) is involved in mediating the wasting effect. To date, a causal relationship between TNF-α signaling and muscle wasting has been established in animal models. However, results from clinical trials are conflicting. This is partly due to the fact that other factors such as TNF-like weak inducer of apoptosis (TWEAK) and interleukin 6 (IL-6) are also involved in skeletal muscle wasting. Because muscle wasting is often associated with physical inactivity and reduced food intake, therapeutic interventions will be most effective when multiple approaches are used in conjunction with nutritional support and exercise.

Particle Radiation-Induced Nontargeted Effects in Bone-Marrow-Derived Endothelial Progenitor Cells

Bone-marrow- (BM-) derived endothelial progenitor cells (EPCs) are critical for endothelial cell maintenance and repair. During future space exploration missions astronauts will be exposed to space irradiation (IR) composed of a spectrum of low-fluence protons ((1)H) and high charge and energy (HZE) nuclei (e.g., iron-(56)Fe) for extended time. How the space-type IR affects BM-EPCs is limited. In media transfer experiments in vitro we studied nontargeted effects induced by (1)H- and (56)Fe-IR conditioned medium (CM), which showed significant increase in the number of p-H2AX foci in nonirradiated EPCs between 2 and 24 h. A 2-15-fold increase in the levels of various cytokines and chemokines was observed in both types of IR-CM at 24 h. Ex vivo analysis of BM-EPCs from single, low-dose, full-body (1)H- and (56)Fe-IR mice demonstrated a cyclical (early 5-24 h and delayed 28 days) increase in apoptosis. This early increase in BM-EPC apoptosis may be the effect of direct IR exposure, whereas late increase in apoptosis could be a result of nontargeted effects (NTE) in the cells that were not traversed by IR directly. Identifying the role of specific cytokines responsible for IR-induced NTE and inhibiting such NTE may prevent long-term and cyclical loss of stem and progenitors cells in the BM milieu.