Inhibition of L-type calcium channels by internal GTP [γS] in mouse pancreatic β cells

Pretreatment of pancreatic cells with pertussis toxin resulted in a 30% increase in peak whole-cell Ca²⁺ currents recorded in the absence of exogenous intracellular guanine nucleotides. Intracellular application of 90 M GTP[S], by liberation from a caged precursor, resulted in 40% reduction of the peak Ca²⁺ current irrespective of whether the current was carried by Ca²⁺ or Ba²⁺. Effects on the delayed outward K⁺ current were small and restricted to a transient Ca²⁺-dependent K⁺ current component. Inhibition by GTP[S] of the Ca²⁺ current was not mimicked by standard GTP and could not be prevented either by pretreatment with pertussis toxin or by inclusion of GDP[S] or cyclic AMP in the intracellular medium. The inhibitory effect of GTP[S] could be counteracted by a prepulse to a large depolarizing voltage. A similar effect of a depolarizing prepulse was observed in control cells with no exogenous guanine nucleotides. These observations indicate that inhibition of cell Ca²⁺ current by G protein activation results from direct interaction with the channel and does not involve second-messenger systems. Our findings also suggest that the cell Ca²⁺ current is subject to resting inhibition by G proteins.     

Inhibition of TNF receptor signaling by anti-TNFα biologicals primes naïve CD4 T cells towards IL-10 T cells with a regulatory phenotype and function

TNFα is a potent pro-inflammatory cytokine playing a pivotal role in several autoimmune diseases. Little is known about the mechanism of TNFα blocking agents on naïve T cell differentiation. Here, we report that neutralizing TNFα during priming of naïve CD4⁺ T cells by dendritic cells favors development of IL-10⁺ T helper cells. TNFα counteracts IL-10⁺ T cell priming mainly via TNFRI receptor signaling. While initial T cell activation was not affected, neutralization of TNFα negatively affected sustained T cell differentiation in later stages of T cell priming. Whole genome gene expression analysis revealed an extended regulatory gene profile for anti-TNFα-treated T cells. Indeed, neutralizing TNFα during naïve T cell priming enhanced the suppressive function of anti-TNFα-treated T cells. Taken together, inhibition of TNFα–TNFR interaction shifts the balance of Th cell differentiation towards IL-10 expressing suppressive T cells, which may be one of the beneficial mechanisms in TNFα blocking therapies.     

Mechanism of bone marrow mesenchymal stem cells secreting miR-26a exosomes affecting high glucose-induced skin fibroblasts function by regulating TLR4/NF-κB signaling

Inflammation Research - The aim of this study was to investigate the molecular mechanism of human bone marrow mesenchymal stem cells (hMSCs) secreting miR-26a exosomes on the function of skin...