Endogenous Production of Hydrogen Sulfide in Isolated Bovine Eye

Abstract

Hydrogen sulfide (H(2)S) is a novel gasotransmitter with physiological and pathological functions in vascular homeostasis, cardiovascular system and central nervous system. In the present study, we determined the endogenous levels of H(2)S in various tissues of the bovine eye. We also examined the basal levels of H(2)S in response to donors (sodium hydrosulfide, NaHS and sodium sulfide, Na(2)S), substrate (L: -cysteine), inhibitors (propargylglycine, PAG and aminooxyacetic acid, AOA) and activator (S-adenosyl-L: -methionine, SAM) of this gas in the bovine retina. H(2)S was measured using a well established spectrophotometric method. The highest concentration of endogenous H(2)S was detected in cornea (19 ± 2.85 nmoles/mg protein, n = 6) and retina (17 ± 2.1 nmoles/mg protein, n = 6). Interestingly, H(2)S was not present in vitreous humor. The inhibitors of CSE and CBS; PAG (1 mM) and AOA (1 mM), significantly attenuated the production of H(2)S in the bovine retina by 56.8 and 42%, respectively. On the other hand the activator of CBS; SAM (100 μM), H(2)S donors; NaHS (1 μM) and Na(2)S (100 μM), significantly increased endogenous levels of H(2)S in bovine retina. L: -cysteine (10-300 μM) produced a significant (P < 0.05) concentration-dependent increase in H(2)S levels reaching a maximal at 300 μM. We conclude that H(2)S is endogenously produced in various tissues of the isolated bovine eye. Moreover, endogenous levels of H(2)S are enhanced in the presence of substrate (L: -cysteine), an activator of CBS (SAM) and H(2)S donors but are blocked by inhibitors of enzymes that synthesize this gas in neural retina.

Effect of Hydrogen Sulfide Donors on Intraocular Pressure in Rabbits

“…The presence and distribution of enzymes responsible for the biosynthesis of H 2 S in ocular tissues (such as CBS and CSE) have been reported by several investigators. [5][6][7][8] Interestingly, insufficiency of CBS due to a deficiency in the gene encoding this enzyme has been linked to some ocular disorders such as retinal detachment and acute glaucoma. 9 In addition to enzymes of the transsulfuration pathway involved in the production of IOP, intraocular pressure; SEM, standard error of the mean.…”

“…[2][3][4] Both CBS and CSE have been localized in mammalian ocular tissues suggesting a potential physiological/pharmacological relevance for H 2 S in the mammalian eye. [5][6][7][8] Indeed, there is a correlation between the expression of enzymes of the biosynthetic pathways for H 2 S production with the endogenous production of this gas in ocular tissues. 6,8 Deficiency of CBS has been associated with ocular diseases such as lens dislocation, retina degeneration, retinal detachment, and acute glaucoma.…”

“…[5][6][7][8] Indeed, there is a correlation between the expression of enzymes of the biosynthetic pathways for H 2 S production with the endogenous production of this gas in ocular tissues. 6,8 Deficiency of CBS has been associated with ocular diseases such as lens dislocation, retina degeneration, retinal detachment, and acute glaucoma. 9 In the bovine isolated neural retina, inhibitors of CSE and CBS have been reported to reduce endogenous production of H 2 S, whereas an activator of CBS, S-adenosyl-l-methionine, enhanced the biosynthesis of this gas confirming the involvement of enzymes of the transsulfuration pathway in this tissue.…”

“…9 In the bovine isolated neural retina, inhibitors of CSE and CBS have been reported to reduce endogenous production of H 2 S, whereas an activator of CBS, S-adenosyl-l-methionine, enhanced the biosynthesis of this gas confirming the involvement of enzymes of the transsulfuration pathway in this tissue. 8 In addition to the demonstration of an in situ production of H 2 S, there is evidence in favor of a pharmacological role for this gas in mammalian ocular tissues. In the anterior uvea, H 2 S donors such as NaHS and Na 2 S inhibited fieldstimulated [ 3 H] norepinephrine release and reduced catecholamine concentrations from isolated porcine iris-ciliary bodies.…”

NaHS induces relaxation response in prostaglandin F2α precontracted bovine retinal arteries partially via Kv and Kir channels

“…The CBS was shown to be largely found in the conjunctiva, cornea, iris and retina of the mammals (Persa et al, 2006;Pong et al, 2007). An endogenous production of H 2 S was observed in various ocular tissues of the bovine eye with the highest levels in the retina and cornea (Kulkarni et al, 2011). H 2 S was also demonstrated to modulate Ca þþ influx (Mikami et al, 2011) and stimulate cyclic AMP production in mammalian retinas and relax ocular smooth muscles (Kulkarni et al, 2009;Monjok et al, 2008).…”