Extracellular ubiquitin protects cardiomyocytes during ischemia/hypoxia by inhibiting mitochondrial apoptosis pathway through CXCR4

Almost 50 Years of Monomeric Extracellular Ubiquitin (eUb)

Monomeric ubiquitin (Ub) is a 76-amino-acid highly conserved protein found in eukaryotes. The biological activity of Ub first described in the 1970s was extracellular, but it quickly gained relevance due to its intracellular role, i.e., post-translational modification of intracellular proteins (ubiquitination) that regulate numerous eukaryotic cellular processes. In the following years, the extracellular role of Ub was relegated to the background, until a correlation between higher survival rate and increased serum Ub concentrations in patients with sepsis and burns was observed. Although the mechanism of action (MoA) of extracellular ubiquitin (eUb) is not yet well understood, further studies have shown that it may ameliorate the inflammatory response in tissue injury and multiple sclerosis diseases. These observations, compounded with the high stability and low immunogenicity of eUb due to its high conservation in eukaryotes, have made this small protein a relevant candidate for biotherapeutic development. Here, we review the in vitro and in vivo effects of eUb on immunologic, cardiovascular, and nervous systems, and discuss the potential MoAs of eUb as an anti-inflammatory, antimicrobial, and cardio- and brain-protective agent.

Macrophages in the Inflammatory Phase following Myocardial Infarction: Role of Exogenous Ubiquitin

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. One of the most common implications of CVD is myocardial infarction (MI). Following MI, the repair of the infarcted heart occurs through three distinct, yet overlapping phases of inflammation, proliferation, and maturation. Macrophages are essential to the resolution of the inflammatory phase due to their role in phagocytosis and efferocytosis. However, excessive and long-term macrophage accumulation at the area of injury and dysregulated function can induce adverse cardiac remodeling post-MI. Ubiquitin (UB) is a highly evolutionarily conserved small protein and is a normal constituent of plasma. Levels of UB are increased in the plasma during a variety of pathological conditions, including ischemic heart disease. Treatment of mice with UB associates with decreased inflammatory response and improved heart function following ischemia/reperfusion injury. This review summarizes the role of macrophages in the infarct healing process of the heart post-MI, and discusses the role of exogenous UB in myocardial remodeling post-MI and in the modulation of macrophage phenotype and function.

Post-ischemic cardioprotective potential of exogenous ubiquitin in myocardial remodeling late after ischemia/reperfusion injury

AIMS

Pretreatment with ubiquitin (UB) associates with preservation of heart function 3 days post-ischemia/reperfusion (I/R) injury. This study investigated the cardioprotective potential of exogenous UB late after myocardial I/R injury. To enhance the clinical relevance, UB treatment was started at the time of reperfusion and continued for 28 days post-I/R.

MAIN METHODS

Mice underwent ligation of the left anterior descending coronary artery for 45 min. At the time of reperfusion, mice were treated with UB or saline which was continued until 28 days post-I/R. Heart function was measured at 3, 7, 14 and 28 days post-I/R using echocardiography. Biochemical parameters of the heart and serum cytokines/chemokines levels were measured 28 days post-I/R.

KEY FINDINGS

I/R decreased heart function and induced LV dilation at all time points post-I/R. However, I/R + UB exhibited improved heart function throughout the observation period, while LV dilation was lower in I/R + UB group at 3, 14 and 28 days post-I/R. I/R-mediated increase in myocardial fibrosis, hypertrophy and apoptosis were significantly lower in I/R + UB vs. I/R. Collagen-1α1 and MMP-2 expression was lower, while MMP-9 and TIMP-2 expression was higher in I/R + UB vs. I/R. MYH-7B (hypertrophy marker) expression was lower in I/R + UB vs. I/R. GSK3β activation was lower (vs. Sham), while activation of ERK1/2 (vs. I/R) and AKT (vs. Sham) was higher in I/R + UB. Serum levels of IL-6, G-CSF and IL-2 were lower in I/R + UB vs. I/R.

SIGNIFICANCE

Post-ischemic UB treatment improves heart function, and associates with decreased myocardial fibrosis, apoptosis, hypertrophy and serum cytokine/chemokine levels.

Perfluorooctane sulfonate induces suppression of testosterone biosynthesis via Sertoli cell-derived exosomal/miR-9-3p downregulating StAR expression in Leydig cells

Perfluorooctane sulfonate (PFOS) is associated with male reproductive disorder, but the related mechanisms are still unclear. In this study, we used in vivo and in vitro models to explore the role of Sertoli cell-derived exosomes (SC-Exo)/miR-9-3p/StAR signaling pathway on PFOS-induced suppression of testosterone biosynthesis. Forty male ICR mice were orally administrated PFOS (0.5-10 mg/kg/bw) for 4 weeks. Bodyweight, organ index, sperm count, reproductive hormones were evaluated. Primary Sertoli cells and Leydig cells were used to delineate the molecular mechanisms that mediate the effects of PFOS on testosterone biosynthesis. Our results demonstrated that PFOS dose-dependently induced a decrease in sperm count, low levels of testosterone, and damage in testicular interstitium morphology. In vitro models, PFOS significantly increased miR-9-3p levels in Sertoli cells and SC-Exo, accompanied by a decrease in testosterone secretion and StAR expression in Leydig cells when Leydig cells were exposed to SC-Exo. Meanwhile, inhibition of SC-Exo or miR-9-3p by their inhibitors significantly rescued PFOS-induced decreases in testosterone secretion and the mRNA and protein expression of the StAR gene in Leydig cells. In summary, the present study highlights the role of the SC-Exo/miR-9-3p/StAR signaling pathway in PFOS-induced suppression of testosterone biosynthesis, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.