Ca mediates axotomy-induced necrosis and apoptosis of satellite glial cells remote from the transection site in the isolated crayfish mechanoreceptor.

Severe nerve injury such as axotomy induces neuron degeneration and death of surrounding glial cells. Using a crayfish stretch receptor that consists of a single mechanoreceptor neuron enveloped by satellite glia, we showed that axotomy not only mechanically injures glial cells at the transection location, but also induces necrosis or apoptosis of satellite glial cells remote from the transection site. We studied Carole in spontaneous or axotomy-induced death of remote glial cells. Stretch receptors were isolated using the original technique that kept the neuron connected to the ventral cord ganglion (control preparations). Using Ca-sensitive fluorescence probe fluo-4, we showed Ca accumulation in neuronal perikarion and glial envelope. Ca gradually accumulated in glial cells after axotomy. In saline with triple Ca concentration the axotomy-induced apoptosis of glial cells increased, but spontaneous or axotomy-induced necrosis was unexpectedly reduced. Saline with 1/3[Ca], oppositely, enhanced glial necrosis. Application of ionomycin, CdCl, thapsigargin, and ryanodine showed the involvement of Ca influx through ionic channels in the plasma membrane, inhibition of endoplasmic reticulum Ca-ATPase, and Ca release from endoplasmic reticulum through ryanodine receptors in axotomy-induced glial necrosis. Apoptosis of glial cells surrounding axotomized neurons was promoted by ionomycin and thapsigargin. Possibly, other Ca sources such as penetration through the plasma membrane contributed to axotomy-induced apoptosis and necrosis of remote glial cells. Thus, modulating different pathways that maintain calcium homeostasis, one can modulate axotomy-induced death of glial cells remote from the transection site.