A role for zinc in regulating hypoxia-induced contractile events in pulmonary endothelium

Abstract

We previously reported that zinc thiolate signaling contributes to hypoxic contraction of small, nonmuscularized arteries of the lung. The present studies were designed to investigate mechanisms by which hypoxia-released zinc induces contraction in isolated pulmonary endothelial cells and to delineate the signaling pathways involved in zinc-mediated changes in the actin cytoskeleton. We used fluorescence-based imaging to show that hypoxia induced time-dependent increases in actin stress fibers that were reversed by the zinc chelator, N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN). We further showed that hypoxia-induced phosphorylation of the contractile protein myosin light chain (MLC) and assembly of actin stress fibers were each TPEN sensitive. Hypoxia and zinc-induced inhibition of MLC phosphatase (MLCP) were independent of the regulatory subunit (MYPT1) of MLCP, and therefore hypoxia-released zinc likely inhibits MLCP at its catalytic (PP1) subunit. Inhibition of PKC by Ro-31-8220 and a dominant-negative construct of PKC-ε attenuated hypoxia-induced contraction of isolated pulmonary endothelial cells. Furthermore, zinc-induced phosphorylation of MLC (secondary to inhibition of MLCP) was PKC dependent, and hypoxia-released zinc promoted the phosphorylation of the PKC substrate, CPI-17. Collectively, these data suggest a link between hypoxia, elevations in labile zinc, and activation of PKC, which in turn acts through CPI-17 to inhibit MLCP activity and promote MLC phosphorylation, ultimately inducing stress fiber formation and endothelial cell contraction.

The zinc transporter ZIP12 regulates the pulmonary vascular response to chronic hypoxia

“…ZIP12 expression may increase PVR by increasing pulmonary vascular tone. Zinc-thiolate signaling has been reported to mediate the constriction of pulmonary microvascular endothelial cells in acute hypoxia through activation of protein kinase C and inhibition of myosin light chain phosphatase, inducing stress fibre formation and endothelial cell contraction 12 . We have shown that ZIP12 targeted siRNA attenuates stress fibre formation in human pulmonary vascular smooth muscle cells cultured in hypoxia (Extended Data Fig.…”

Quantum Blue Reduces the Severity of Woody Breast Myopathy via Modulation of Oxygen Homeostasis-Related Genes in Broiler Chickens

“…Although a mechanistic interaction between minerals and WB myopathy is lacking, our data suggest that WB might be associated with mineral overload/deficiency. It has been shown that hypoxia increases intracellular Zn levels (Bernal et al, 2008) and intracellular Zn overload has been reported to alter skeletal muscle contractility (Isaacson and Sandow, 1963; Bernal et al, 2011). Hypoxia was also found to increase basal Ca and Na concentrations, and reduce K and P levels (Weiss et al, 1989; Yadav et al, 2013; Shi et al, 2014).…”

Zn2+ chelation by serum albumin improves hexameric Zn2+-insulin dissociation into monomers after exocytosis

“…Islets' β-cells are close to the fenestrated endothelium ( Fig 5 ), building a functional unit that is lost in islet transplantation procedures [ 36 , 37 ]. In other organs, such as the lung, free Zn 2+ induces endothelial cell contraction [ 38 ], a process that is augmented by nitric oxide [ 39 , 40 ]. This mechanism might also operate in pancreatic islets in hypoxic conditions in a process dependent on the generation of high levels of nitric oxide [ 41 , 42 ].…”