These effects include the ability of H 2S to inhibit leukocyte adherence to the vascular endothelium and the subsequent extravasation of leukocytes ( 72).
![hydrogen sulfide hydrogen sulfide](https://eoimages.gsfc.nasa.gov/images/imagerecords/85000/85338/namibia_amo_2015046_lrg.jpg)
Figure 1 summarizes some of the key effects of H 2S with respect to inflammation and injury. Moreover, there are now substantial data supportive of a role of H 2S in promoting resolution of inflammation and healing of injured tissue. As was the case for nitric oxide, the literature on H 2S in inflammation was initially contradictory, but in recent years a general pattern has emerged consistent with this mediator exerting anti-inflammatory effects, except at high concentrations ( 56). Several studies have subsequently highlighted the importance of H 2S in inflammation ( 27, 30, 54, 56). One of the first physiological effects of H 2S that was identified was its ability to relax vascular smooth muscle ( 73, 75), resulting in vasodilation, a hallmark of inflammation. The use of H 2S as a therapeutic modality is also reviewed, along with the potential effects of bacteria-derived H 2S in modulating inflammation and mucosal integrity in the digestive tract and possibly in other organs. In this article, the ability of H 2S to modulate inflammation is reviewed, with a particular focus on the role of the mediator in resolution of inflammation.
![hydrogen sulfide hydrogen sulfide](https://i.ytimg.com/vi/VkGhM9ZrKI4/maxresdefault.jpg)
Also, attempts have been made to exploit the beneficial effects of each of the three gaseous mediators in designing novel therapeutic agents. All three of these mediators bind to hemoglobin ( 48, 63) and can influence activity and/or expression of enzymes responsible for synthesis of the other gaseous mediators ( 24, 39, 73– 75). All three mediators have very short half-lives in vivo and produce primarily beneficial effects at physiological concentrations while contributing to injury at super-physiological concentrations. Enzymes for the synthesis of all three of these gaseous mediators have been identified and more continue to be identified, at least in the case of H 2S ( 50). There are many similarities among H 2S, carbon monoxide, and nitric oxide. Indeed, as was the case for two other gaseous mediators (nitric oxide and carbon monoxide), the physiological effects of H 2S were overshadowed by the toxicity associated with high concentrations of this substance ( 44). W hile clinical benefits of hydrogen sulfide, at least in the context of sulfur hot springs, have been espoused for centuries, it is only in the past 20 years that H 2S has been recognized as an important mediator of physiological processes ( 1, 74). Results from animal studies suggest that H 2S-releasing agents are promising therapeutic agents for many indications, but these compounds need to be assessed in a clinical setting. Future Directions: Improvements in methods for measurement of H 2S and development of more selective inhibitors are crucial for gaining a better understanding of the pathophysiological importance of this mediator. A compromise of this barrier could result in modulation of mucosal function and integrity by bacterial H 2S. Enterocytes and colonocytes thereby represent a “metabolic barrier” to the diffusion of bacteria-derived H 2S into the subepithelial space. Critical Issues: Enteric bacteria can be a significant source of H 2S, which could affect mucosal integrity indeed, luminal H 2S can serve as an alternative to oxygen as a metabolic substrate for mitochondrial respiration in epithelial cells. H 2S has been exploited in the design of more effective and safe anti-inflammatory drugs.
![hydrogen sulfide hydrogen sulfide](https://www.safetycourses.us/wp-content/uploads/2020/10/HydrogenSulfideAwareness.jpg)
On the other hand, suppression of endogenous H 2S synthesis impairs mucosal defense and leads to increased granulocyte infiltration. Recent Advances: In the gastrointestinal tract, H 2S has been shown to promote healing of ulcers and the resolution of mucosal inflammation.
![hydrogen sulfide hydrogen sulfide](https://c2.staticflickr.com/2/1284/532580667_5f75a50341_z.jpg)
Significance: Hydrogen sulfide is emerging as an important mediator of many aspects of inflammation, and perhaps most importantly as a factor promoting the resolution of inflammation and repair of injury.