TRPA1, but not TRPV1, is involved in the increase of the non-adrenergic non-cholinergic outflow induced by hydrogen sulfide in pithed rats

Hydrogen sulfide as a neuromodulator of the vascular tone

Hydrogen sulfide (H₂S) is a unique signaling molecule that, along with carbon monoxide and nitric oxide, belongs to the gasotransmitters family. H₂S is endogenously synthesized by enzymatic and non-enzymatic pathways. Three enzymatic pathways involving cystathionine-γ-lyase, cystathionine-β-synthetase, and 3-mercaptopyruvate sulfurtransferase are known as endogenous sources of H₂S. This gaseous molecule has recently emerged as a regulator of many systems and physiological functions, including the cardiovascular system where it controls the vascular tone of small arteries. In this context, H₂S leads to vasorelaxation by regulating the activity of vascular smooth muscle cells, endothelial cells, and perivascular nerves. Specifically, H₂S modulates the functionality of different ion channels to inhibit the autonomic sympathetic outflow-by either central or peripheral mechanisms-or to stimulate perivascular sensory nerves. These mechanisms are particularly relevant for those pathological conditions associated with impaired neuromodulation of vascular tone. In this regard, exogenous H₂S administration efficiently attenuates the increased activity of the sympathetic nervous system often seen in patients with certain pathologies. These effects of H₂S on the autonomic sympathetic outflow will be the primary focus of this review. Thereafter, we will discuss the central and peripheral regulatory effects of H₂S on vascular tone. Finally, we will provide the audience with a detailed summary of the current pathological implications of H₂S modulation on the neural regulation of vascular tone.

Targeting hydrogen sulfide and nitric oxide to repair cardiovascular injury after trauma

The systemic cardiovascular effects of major trauma, especially neurotrauma, contribute to death and permanent disability in trauma patients and treatments are needed to improve outcomes. In some trauma patients, dysfunction of the autonomic nervous system produces a state of adrenergic overstimulation, causing either a sustained elevation in catecholamines (sympathetic storm) or oscillating bursts of paroxysmal sympathetic hyperactivity. Trauma can also activate innate immune responses that release cytokines and damage-associated molecular patterns into the circulation. This combination of altered autonomic nervous system function and widespread systemic inflammation produces secondary cardiovascular injury, including hypertension, damage to cardiac tissue, vascular endothelial dysfunction, coagulopathy and multiorgan failure. The gasotransmitters nitric oxide (NO) and hydrogen sulfide (H2S) are small gaseous molecules with potent effects on vascular tone regulation. Exogenous NO (inhaled) has potential therapeutic benefit in cardio-cerebrovascular diseases, but limited data suggests potential efficacy in traumatic brain injury (TBI). H2S is a modulator of NO signaling and autonomic nervous system function that has also been used as a drug for cardio-cerebrovascular diseases. The inhaled gases NO and H2S are potential treatments to restore cardio-cerebrovascular function in the post-trauma period.