H2S counteracts proinflammatory effects of LPS through modulation of multiple pathways in human cells

BACKGROUND

Hydrogen sulfide donors reduce inflammatory signaling in vitro and in vivo. The biological effect mediated by H₂S donors depends on the kinetics of the gas release from the donor molecule. However, the molecular mechanisms of H₂S-induced immunomodulation were poorly addressed. Here, we studied the effect of two different hydrogen sulfide (H₂S)-producing agents on the generation of the LPS-induced inflammatory mediators. Importantly, we investigated the transcriptomic changes that take place in human cells after the LPS challenge, combined with the pretreatment with a slow-releasing H₂S donor-GYY4137.

METHODS

We investigated the effects of GYY4137 and sodium hydrosulfide on the release of proinflammatory molecules such as ROS, NO and TNF-α from LPS-treated human SH-SY5Y neuroblastoma and the THP-1 promonocytic cell lines. Transcriptomic and RT-qPCR studies using THP-1 cells were performed to monitor the effects of the GYY4137 on multiple signaling pathways, including various immune-related and proinflammatory genes after combined action of LPS and GYY4137.

RESULTS

The GYY4137 and sodium hydrosulfide differed in the ability to reduce the production of the LPS-evoked proinflammatory mediators. The pre-treatment with GYY4137 resulted in a drastic down-regulation of many TNF-α effectors that are induced by LPS treatment in THP-1 cells. Furthermore, GYY4137 pretreatment of LPS-exposed cells ameliorates the LPS-mediated induction of multiple pro-inflammatory genes and decreases expression of immunoproteasome genes. Besides, in these experiments we detected the up-regulation of several important pathways that are inhibited by LPS.

CONCLUSION

Based on the obtained results we believe that our transcriptomic analysis significantly contributes to the understanding of the molecular mechanisms of anti-inflammatory and cytoprotective activity of hydrogen sulfide donors, and highlights their potential against LPS challenges and other forms of inflammation.

Nitric oxide production by peritoneal macrophages from aged rats: A short term and direct modulation by citrulline

Citrulline has anti-inflammatory properties and exerts beneficial effects on various impaired functions in aging. However, there are few data on citrulline action on immune function in aged populations. The objective of the study was to evaluate citrulline ability, after in vivo and in vitro administration, to modulate macrophage functions in aged rats and the possible pathways involved. Twenty-one-month-old Sprague-Dawley rats (n = 27) received a citrulline supplementation at 5 g/kg/d for 5 days, or an isonitrogenous diet, and peritoneal macrophages were cultured with or without LPS. In the in vitro study, macrophages from 22-month-old rats (n = 16) were cultured with or without LPS, citrulline and inhibitors of different inflammatory pathways (n = 8/conditions). Nitric oxide (NO) and tumor necrosis factor α (TNFα) production were measured in both in vivo and in vitro studies. Citrulline decreased NO production variability by peritoneal macrophages after in vivo administration (p = 0.0034) and downregulated NO production by 22% after in vitro administration (95% CI: [6%; 35%]; p = 0.0394), without any direct effect on TNFα production. None of the transductional pathways explored seem to be involved. Citrulline slightly modulates NO production in vivo and in vitro, suggesting a possible action through modulation of arginine metabolism in macrophages rather than a direct transductional effect. The pleiotropic effects of citrulline in aging could be due, at least in part, to the anti-inflammatory effect of citrulline.