Abstract
Purpose: :
Programmed cell death is a phenomenon associated with both neural development and pathological conditions. During retina neural development, cell death affects various cell populations, including retinal ganglion cells (RGC). On the other hand, RGC death is also a hallmark of retinal diseases, such as optic neuropathies. Several factors are involved in the regulation of the RGC death, including cytokines such as Interleukin-2 (IL-2), a prototypical pro-inflammatory cytokine that exerts pleiotrophic functions in several areas of the central nervous system. The aim of this study was to investigate in vitro: (i) the neuroprotective effect of interleukin (IL)-2 upon axotomized RGC; (ii) the intracellular signaling pathways related to the neuroprotective effect of IL-2.
Methods: :
Newborn Lister Hooded rats were anaesthetized by hypothermia and received injections of rhodamine dextran (RD) in their superior colliculus for retrograde labelling of RGC. After 2 days, retinal explants were obtained and maintained with or without IL-2 (50U/mL), and/or specifics pharmacological inhibitors for 2 or 5 days in vitro (DIV). The total number of nuclei (stained with DAPI) in the ganglion cell layer and the specific number of RGC labeled with RD were counted using fluorescence microscopy. Western Blot and immunohistochemical analysis were performed to verify protein expression in retinal tissue.
Results: :
The results showed that 50 U/mL IL-2 treatment blocks axotomy-induced RGC death (2 DIV: 85.43 ± 5.43; 5 DIV: 50.23 ± 5.32). Pharmacological analysis demonstrated that RGC survival mediated by IL-2 is dependent of tyrosine kinase, Janus kinase (JAK), and extracellular signal-regulated kinases (Erk1/2) activity. Moreover, the IL-2 treatment increased the phosphorilation of both Erk1/2 and Akt (~two fold), although its neuroprotective effect upon RGC was only dependent of JAK and Erk 1/2 activity.
Conclusions: :
Our data demonstrate that IL-2 promotes a long term (2 and 5 DIV) neuroprotective effect upon axotomized RGC in a retina explants model, and this effect is related to tyrosine kinase, JAK, and ERK1/2 activity.
Keywords: ganglion cells • cell survival • cytokines/chemokines