Oligodendrocytes have recently been implicated in the pathophysiology of amyotrophic lateral sclerosis (ALS). Here we show that, in vitro, mutant superoxide dismutase 1 (SOD1) mouse oligodendrocytes induce WT motor neuron (MN) hyperexcitability and death. Moreover, we efficiently derived human oligodendrocytes from a large number of controls and patients with sporadic and familial ALS, using two different reprogramming methods. All ALS oligodendrocyte lines induced MN death through conditioned medium (CM) and in coculture. CM-mediated MN death was associated with decreased lactate production and release, whereas toxicity in coculture was lactate-independent, demonstrating that MN survival is mediated not only by soluble factors. Remarkably, human SOD1 shRNA treatment resulted in MN rescue in both mouse and human cultures when knockdown was achieved in progenitor cells, whereas it was ineffective in differentiated oligodendrocytes. In fact, early SOD1 knockdown rescued lactate impairment and cell toxicity in all lines tested, with the exclusion of samples carrying chromosome 9 ORF 72 (C9orf72) repeat expansions. These did not respond to SOD1 knockdown nor did they show lactate release impairment. Our data indicate that SOD1 is directly or indirectly involved in ALS oligodendrocyte pathology and suggest that in this cell type, some damage might be irreversible. In addition, we demonstrate that patients with C9ORF72 represent an independent patient group that might not respond to the same treatment.oligodendrocytes | amyotrophic lateral sclerosis | SOD1 | C9orf72 | lactate

The acid sensing ion channels (ASICs) are proton-gated cation channels expressed throughout the nervous system. ASICs are activated during acidic pH fluctuations, and recent work suggests that they are involved in excitatory synaptic transmission. ASICs can also induce neuronal degeneration and death during pathological extracellular acidosis caused by ischemia, autoimmune inflammation, and traumatic injury. Many endogenous neuromodulators target ASICs to affect their biophysical characteristics and contributions to neuronal activity. One of the most unconventional types of modulation occurs with the interaction of ASICs and neuropeptides. Collectively, FMRFamide-related peptides and dynorphins potentiate ASIC activity by decreasing the proton-sensitivity of steady state desensitization independent of G protein-coupled receptor activation. By decreasing the proton-sensitivity of steady state desensitization, the FMRFamide-related peptides and dynorphins permit ASICs to remain active at more acidic basal pH. Unlike the dynorphins, some FMRFamide-related peptides also potentiate ASIC activity by slowing inactivation and increasing the sustained current. Through mechanistic studies, the modulation of ASICs by FMRFamide-related peptides and dynorphins appears to be through distinct interactions with the extracellular domain of ASICs. Dynorphins are expressed throughout the nervous system and can increase neuronal death during prolonged extracellular acidosis, suggesting that the interaction between dynorphins and ASICs may have important consequences for the prevention of neurological injury. The overlap in expression of FMRFamide-related peptides with ASICs in the dorsal horn of the spinal cord suggests that their interaction may have important consequences for the treatment of pain during injury and inflammation.

Yi T, Vick JS, Vecchio MJ, Begin KJ, Bell SP, Delay RJ, Palmer BM. Identifying cellular mechanisms of zinc-induced relaxation in isolated cardiomyocytes. Am J Physiol Heart Circ Physiol 305: H706-H715, 2013. First published June 28, 2013 doi:10.1152/ajpheart.00025.2013.-We tested several molecular and cellular mechanisms of cardiomyocyte contraction-relaxation function that could account for the reduced systolic and enhanced diastolic function observed with exposure to extracellular Zn 2ϩ . Contraction-relaxation function was monitored in isolated rat and mouse cardiomyocytes maintained at 37°C, stimulated at 2 or 6 Hz, and exposed to 32 M Zn 2ϩ or vehicle. Intracellular Zn 2ϩ detected using FluoZin-3 rose to a concentration of ϳ13 nM in 3-5 min. Peak sarcomere shortening was significantly reduced and diastolic sarcomere length was elongated after Zn 2ϩ exposure. Peak intracellular Ca 2ϩ detected by Fura-2FF was reduced after Zn 2ϩ exposure. However, the rate of cytosolic Ca 2ϩ decline reflecting sarcoplasmic reticulum (SR) Ca 2ϩ -ATPase (SERCA2a) activity and the rate of Na ϩ /Ca 2ϩ exchanger activity evaluated by rapid Na ϩ -induced Ca 2ϩ efflux were unchanged by Zn 2ϩ exposure. SR Ca 2ϩ load evaluated by rapid caffeine exposure was reduced by ϳ50%, and L-type calcium channel inward current measured by whole cell patch clamp was reduced by ϳ70% in cardiomyocytes exposed to Zn 2ϩ . Furthermore, ryanodine receptor (RyR) S2808 and phospholamban (PLB) S16/T17 were markedly dephosphorylated after perfusing hearts with 50 M Zn 2ϩ . Maximum tension development and thinfilament Ca 2ϩ sensitivity in chemically skinned cardiac muscle strips were not affected by Zn 2ϩ exposure. These findings suggest that Zn 2ϩ suppresses cardiomyocyte systolic function and enhances relaxation function by lowering systolic and diastolic intracellular Ca 2ϩ concentrations due to a combination of competitive inhibition of Ca 2ϩ influx through the L-type calcium channel, reduction of SR Ca 2ϩ load resulting from phospholamban dephosphorylation, and lowered SR Ca 2ϩ leak via RyR dephosphorylation. The use of the low-Ca 2ϩ -affinity Fura-2FF likely prevented the detection of changes in diastolic Ca 2ϩ and SERCA2a function. Other strategies to detect diastolic Ca 2ϩ in the presence of Zn 2ϩ are essential for future work.cardiac; myocyte; sarcomere; L-type channel; ryanodine receptor THE IMPORTANCE of zinc and zinc ion (Zn 2ϩ ) in cardiac muscle function is only partially understood at this time. Cardiac zinc content correlates positively with ejection fraction (EF) in humans (18), and zinc supplementation to cardioplegic solution protects against the loss of systolic function and enhances diastolic function during and after ischemia-reperfusion injury (23-25). It has been suggested that zinc combats oxidative stress associated with ischemia-reperfusion and diabetes in part by enhancing the capacity of the zinc-binding protein metallothionein (15), which shields against reactive oxygen species (13, 23-25, 27, 36).Zinc deficiency (Ͻ10.7 M plasm...

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The mouse vomeronasal organ (VNO) is a chemosensory structure that regulates many social and fear related behaviors. Social odorants, colloquially known as pheromones, are detected within the lumen of the VNO by bipolar vomeronasal sensory neuron (VSN)s. We have previously shown that adenosine 5’‐triphosphate (ATP), a potent neuromodulator in chemosensory systems, elicits an inward current and action potentials in VSNs through activation of ionotropic P2X receptors. However, it was unclear if G‐protein coupled P2Y receptors were involved in modulating the excitability of VSNs. Using RT‐PCR, we showed that P2Y1, 2, and 6 were expressed in the VNO. Immunohistochemical labeling with antibodies specific to P2Y1 and 2 revealed widespread expression of both receptors in the sensory and nonsensory epithelia. Using whole cell patch clamp, we observed that while ATP was without effect, adenosine 5’‐diphosphate (ADP) hyperpolarized the voltage dependence of sodium channel steady state inactivation in a subset of VSNs. Moreover, neither ATP nor ADP had any effect on the voltage dependence of sodium channel activation or fast inactivation. We hypothesize that following activation of P2X receptors by ATP, the rapid breakdown of ATP to ADP by ubiquitous ecto‐endonucleases would result in a reduction of sodium channel availability through activation of P2Y receptors. Grant Funding Source: NIH