Hydrogen sulfide is synthesized endogenously in both retinal artery and retina mostly via CSE

https://doi.org/10.1016/j.exer.2021.108443Get rights and content

Highlights

  • H2S is produced in bovine eye and its amount varies in eye tissues.

  • 3-MST, CBS, and CSE are present both in retina and in the retinal artery.

  • CBS and CSE were higher in retinal artery than the retina layer.

  • High enzyme levels determined in retinal artery particularly in the endothelial layer.

Abstract

Hydrogen sulfide (H2S) is an important gasotransmitter expressed in various tissues of the organism, including the eye. It is known that H2S is localized especially in the retina and corneal layers in bovine eye. The enzymes that mediate H2S synthesis are 3-mercaptopyruvate sulfurtransferase (3-MST), cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). Herein, we aimed to investigate the concentration levels and distribution profiles of these enzymes in bovine retina and retinal artery. Enzyme levels were measured by ELISA and distribution were determined by immunofluorescence microscopic analysis. Much higher concentrations of CBS and CSE have been detected in the retinal artery compared to the retina. In both tissues, particulary 3-MST was found at the lowest level while, CSE was determined to be the most abundant enzyme among the others. CBS distribution was shown in both endothelial and smooth muscle layers, while CSE was seen especially in the endothelial layer of the retinal artery. In the retina, CBS and CSE were expressed in cone-basil cells and retinal ganglion cells, while CSE was also present in bipolar cells. Our results indicated that H2S is synthesized endogenously in ocular tissues. The widespread expression of H2S synthesizing enzymes in the retina and retinal artery of the bovine eye, which has anatomical similarities with the human eye, may suggest a protective role for H2S against retinal vascular diseases as well as a regulatory role in the retinal vascular tone.

Introduction

H2S is an important gaseous mediator which has several effects such as the regulation of vascular tone in various arteries as well as the anti-apoptotic, anti-inflammatory and anti-oxidant properties (Badiei et al., 2019; Gheibi et al., 2018). It is known that H2S is also present in the eye and has physiological importance. There are 4 main enzymes that provide endogenous synthesis of H2S in the retina layer of the eye: cysteine aminotransferase/3-mercaptopyruvate sulfurtransferase (CAT/3-MST), cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) (Abe and Kimura, 1996; Du et al., 2017; Hughes et al., 2009). CBS and CSE were shown to be expressed in salamander, mouse and rat retina, while 3-MST in mouse and rat retina (Gersztenkorn et al., 2016; Huang et al., 2017; Mikami et al., 2011; Pong et al., 2007; Zeng et al., 2018).

Regarding to H2S, few studies are noticed in bovine eye. High levels of H2S were determined in the cornea and retina by spectrophotometric method. In the presence of the inhibitors of CBS and CSE enzymes namely, aminooxyacetic acid (AOAA) and dl-propargylglycine (PAG), a partial reduction in H2S levels was measured in the retina by 42%–56%, respectively, which revealed the role of CBS and CSE enzymes in the synthesis of H2S in bovine retina (Kulkarni et al., 2011). In addition, in our previous study, it was shown that the H2S donor, NaHS relaxed bovine retinal artery partially by the activation of Kv and Kir channels. Moreover, administration of L-cysteine, the precursor of H2S, induced a moderate relaxation which was significantly reduced in the presence of the (CBS) inhibitor, AOAA (Takir et al., 2015). The functional role of H2S in the regulation of retinal artery tone suggests that H2S can be synthesized endogenously in the retina and retinal artery (Du et al., 2017). However, no studies are evident showing the presence of 3-MST, CBS and CSE enzymes in bovine retina in terms of the molecular or immunohistochemical methods, despite the presentation of CBS and CSE enzymes in mice retina (Gersztenkorn et al., 2016; Mikami et al., 2011). In addition, none of these enzymes have been evaluated in the retinal artery.

Based on the data from previous studies, herein we aimed to evaluate whether the enzymes 3-MST, CBS and CSE that synthesize H2S are expressed in bovine retina and retinal artery. For this purpose, concentration levels and distribution profiles of enzymes were assessed by ELISA and immunofloresence microscobic analysis.

Section snippets

Preparation of bovine retina and retinal arteries

Bovine eyes (Brown Swiss [Montafoner], either sex, 2–4 years of age) were obtained from a local slaughterhouse and transported to the laboratory. Following transfer, extraocular muscles and connective tissues were dissected from the globe, the vitreous was removed and a stereomicroscope was used for dissection procedure (Zeiss, 2000; Oberkochen, Germany). The central retinal artery located underneath the optic disc was isolated completely and detached from the adhering retinal tissue.

The concentration levels of 3-MST, CBS and CSE

The role of 3-MST, CBS and CSE enzymes known to mediate H2S synthesis were evaluated in bovine retina and retinal artery by ELISA method.

Discussion

This study aimed to investigate the presence, amount and distribution of H2S synthesizing enzymes (3-MST, CBS and CSE) in the retinal artery and retina. To the best of our knowledge, this is the first study to evaluate the role of 3-MST, CBS and CSE enzymes in bovine retinal artery. There is also no study on protein levels of these enzymes in bovine retina. In this respect, our study provides original findings regarding the presence of H2S in the retina and retinal circulation, which may make a

Conclusion

The widespread expression of H2S synthesizing enzymes in the retina and the high enzyme levels determined in retinal artery, particularly in the endothelial layer, may suggest a protective role of H2S against retinal vascular diseases as well as a regulatory role in retinal vascular tone. The limitation of the study is that we could not determine the role of enzymes in the retina and retinal artery. Therefore, more studies are needed in this area to determine the activities and functions of

Declaration of competing interest

The authors declare that there is no conflict of interest.

Acknowledgements

This study was funded by TUBITAK (Scientific and Technological Research Council of Turkey) Project Number: 115S196; by Scientific Research Projects Coordination Unit of Istanbul University, Project Number: TDK-2018-29789; and by Scientific Research Projects Coordination Unit of Giresun University, Project Number: SAĞ-BAP-A-230218-81.

References (17)

  • K. Abe et al.

    The possible role of hydrogen sulfide as an endogenous neuromodulator

    J. Neurosci.

    (1996)
  • A. Badiei et al.

    Comparative localization of cystathionine beta synthases and cystathionine gamma lyase in canine, non-human primate and human retina

    Exp. Eye Res.

    (2019)
  • J. Du et al.

    Role of hydrogen sulfide in retinal diseases

    Front. Pharmacol.

    (2017)
  • D. Gersztenkorn et al.

    Hydrogen sulfide contributes to retinal neovascularization in Ischemia-Induced retinopathy

    Investig. Ophthalmol. Vis. Sci.

    (2016)
  • S. Gheibi et al.

    Regulation of vascular tone homeostasis by NO and H2S: implications in hypertension

    Biochem. Pharmacol.

    (2018)
  • Y. Han et al.

    Hydrogen sulfide: a gaseous signaling molecule modulates tissue homeostasis: implications in ophthalmic diseases

    Cell Death Dis.

    (2019)
  • S. Huang et al.

    Relevant variations and neuroprotecive effect of hydrogen sulfide in a rat glaucoma model

    Neuroscience

    (2017)
  • M.N. Hughes et al.

    Making and working with hydrogen sulfide. The chemistry and generation of hydrogen sulfide in vitro and its measurement in vivo: a review

    Free Radic. Biol. Med.

    (2009)
There are more references available in the full text version of this article.

Cited by (7)

  • The role of hydrogen sulfide in the retina

    2023, Experimental Eye Research
  • Imaging fluctuation of sulfite in mouse tumor and inflammation models with a novel quinoxaline-based fluorescent probe

    2022, Sensors and Actuators B: Chemical
    Citation Excerpt :

    In particular, to depict the circulation of sulfur elements in living organisms, the fluctuation of sulfur-containing species has drawn the attention of many investigators in medicinal science and chemical biology [7,8]. Mainly catalyzed by the essential enzymes such as cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 5′-phosphate by 3-mercaptopyruvate sulfur transferase (3-MST) [9–11], the interconversion of the sulfur-containing species in the human lead to typical molecules including sulfur dioxide (SO2), hydrogen sulfide (H2S) and biothiols (glutathione (GSH), cysteine (Cys), homocysteine (Hcy)) [12–15]. Among them, GSH and Hcy have been regarded as significant indexes in blood biochemistry tests, while H2S has been considered as the third gasotransmitter after nitro oxide (NO) and carbon monoxide (CO) [16,17].

View all citing articles on Scopus
View full text