The Carbon monoxide releasing molecule ALF-186 mediates anti-inflammatory and neuroprotective effects via the soluble guanylate cyclase β1 in rats' retinal ganglion cells after ischemia and reperfusion injury

Background: The endogenously produced gaseous molecule carbon monoxide is able to promote organ protection after ischemia-reperfusion injuries (IRI). The impact of carbon monoxide releasing molecules (CORM) regarding inflammation in neuronal tissues has not been studied in detail. In this investigation, we aimed to analyze the effects of the CORM ALF-186 on neuro-inflammation and hypothesized that the soluble guanylate cyclase (sGC) is playing a decisive role. Methods: Retinal ischemia-reperfusion injury was performed for 60 min in Sprague-Dawley rats. Thereafter, the CORM ALF-186 (10 mg/kg) in the presence or absence of the sGC inhibitor ODQ was injected via a tail vein. Retinal tissue was harvested 24 h later to analyze mRNA or protein expression of sGC-B1 subunit, transcription factors NF-.B and CREB, the inflammatory cytokines TNF-alpha and IL-6, as well as the heat shock proteins (HSP) HSP-70 and HSP-90. Immunohistochemistry was performed on frozen sections of the retina. The overall neuroprotective effect of ALF-186 was assessed by counting fluorogold-pre-labeled retinal ganglion cells (RGC) 7 days after IRI. Results: Ischemia-reperfusion mediated loss of vital RGC was attenuated by the administration of ALF-186 after injury. ALF-186 treatment after IRI induced sGC-beta 1 leading to a decreased NF-beta 1 and CREB phosphorylation. Consecutively, ALF-186 mitigated IRI induced TNF-a and IL-6 expression in the retina and in the rats' serum. Moreover, ALF-186 attenuated heat shock protein 70 (Hsp-70) while increasing Hsp-90. The sGC-inhibitor ODQ attenuated the antiinflammatory effects of ALF-186 and increased retinal loss of ganglion cells. These results were confirmed by immunohistochemistry. Conclusion: The CORM ALF-186 protected RGC from IRI induced loss. Furthermore, ALF-186 reduced IRI mediated neuroinflammation in the retina and in the serum by activating sGC. Inhibition of sGC stopped the beneficial and protective effects of ALF-186. ALF-186 may present a promising therapeutic alternative in treating inflammation after neuronal IRI.