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Sunny E Ohia, Leah Bush, Jenaye Robinson, Kalu K Ngele, Catherine A Opere, Ya Fatou N Mbye; REGULATION OF ENDOGENOUS HYDROGEN SULFIDE CONCENTRATIONS BY CANNABINOIDS IN BOVINE ISOLATED RETINA. Invest. Ophthalmol. Vis. Sci. 2020;61(7):5127.
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Both endocannabinoids and hydrogen sulfide (H2S) have been reported to exert neuroprotective actions in nervous tissues (Sakamoto et al., Exp. Eye Res. 120:90, 2014; Schwitzer et al., Eur. Addict. Res. 22:287, 2016). It remains to be determined whether these modulators can interact with each other or share a common pathway in their neuroprotective actions. The aim of the present study was to investigate the pharmacological actions of endocannabinoids on the biosynthesis of H2S in bovine isolated neural retina.
Isolated retinae were homogenized and then exposed to different concentrations of methanandamide (1 nM – 10 μM) and 2-arachidonyl glycerol (2-AG) (1 – 3 μM) for 90 minutes at 37 C. Retinal homogenates were then incubated with ethylenediaminetetraacetic acid (EDTA) (1%), zinc acetate (1%), and borate buffer (pH 11) for 30 mins followed by 10-minute incubation with N, N dimethyl p-phenylenediamine (20 mM) and FeCl3 (300mM). Samples were then centrifuged at 5000 g for three minutes and each supernatant was assessed for H2S content using the well-established Methylene Blue method. To determine the effect of cannabinoids on the intramural biosynthesis of H2S, retinal homogenates were treated L-cysteine (10 µM), a substrate for enzymatic H2S biosynthesis, and methanandamide (10 µM) simultaneously. H2S concentrations in samples were then assessed using the Methylene Blue assay.
Both methanandamide (1 nM - 10 μM) and 2-AG (1 - 3 μM) elicited a concentration-dependent decrease in basal H2S production in the isolated retina. For instance, methanandamide (10 µM) significantly (p <0.05) reduced basal production of H2S by 28% when compared to controls. Likewise, 2-AG (10 µM) also elicited a 22% decrease in basal retinal H2S concentration when compared to controls. In the presence of L-cysteine (10 μM) alone, H2S concentrations was increased by 100% over basal levels (p <0.001), a response that was abolished by methanandamide (10 µM).
We conclude that exogenously applied endocannabinoids can alter the basal production of H2S in the isolated neural retina. Furthermore, endocannabinoids also inhibited L-cysteine-stimulated H2S biosynthesis.The ability of endocannabinoids to interact with the pathway leading to the biosynthesis of H2S suggests that a cross-talk exists between both neuromodulators in the retina.
This is a 2020 ARVO Annual Meeting abstract.
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