How Hydrogen Gas, Nitric Oxide, and H2S All Activate the Same Cellular Defense Switch

Authors
Journal
Medical Gas Research
Year
DOI
10.4103/mgr.MEDGASRES-D-26-00086
Study Type
clinical
Peer Reviewed
Yes
Country
China
Health Condition
Ischemia-Reperfusion Injury
Body System
Cardiovascular

TL;DR

Three "therapeutic gases" — hydrogen, nitric oxide, and hydrogen sulfide — all help protect your cells from damage by activating the same built-in defense system, just in different ways. Scientists think using all three together might work better than using just one, which could someday lead to new treatments for diseases like Alzheimer's, heart attacks, and diabetes.

Key Finding

Molecular hydrogen activates the Nrf2/Keap1 cellular defense pathway indirectly — by reducing oxidative stress upstream — rather than by directly modifying proteins the way nitric oxide and hydrogen sulfide do.

Summary

This review article examines how three therapeutic gases — nitric oxide, hydrogen sulfide, and molecular hydrogen — all influence the same cellular defense system, called the Nrf2/Keap1 pathway (a master switch that helps cells respond to stress and damage). The authors compare the chemistry of each gas, noting that nitric oxide and hydrogen sulfide directly modify proteins, while hydrogen appears to work more indirectly by reducing upstream oxidative stress. The review also explores how these gases may interact with each other and discusses challenges in turning these findings into real medical treatments.

Practical Takeaway

This is a review of existing research, not a clinical trial, so it does not test hydrogen water in people. It suggests that hydrogen may support cellular antioxidant defenses through a distinct biological route, but the authors are clear that major hurdles — including finding the right dose and delivery method — must be solved before any clinical recommendations can be made.

Abstract

The nuclear factor erythroid 2-related factor 2/Kelch-like Ech-associated protein 1 (Nrf2/Keap1) pathway is a central homeostatic module that integrates oxidant, electrophilic, inflammatory, and metabolic signals into adaptive transcriptional programs. In parallel, nitric oxide (NO), hydrogen sulfide (H2S), and molecular hydrogen (H2) have emerged as therapeutically relevant gaseous mediators with distinct chemical identities, tissue distribution profiles, and pharmacological constraints. This review re-examines these gases through a single organizing question: how can highly dissimilar small molecules converge on the same redox-defense hub? We compare the direct cysteine chemistry of NO and H2S with the mainly indirect actions proposed for H2, and we use the Nrf2/Keap1 axis as the mechanistic backbone for that comparison. NO and H2S are best understood as redox-active signaling gases capable of covalent protein modification, whereas H2 appears to act largely by reshaping upstream oxidative events, mitochondrial electron leakage, membrane lipid oxidation products, and stress-responsive signaling states. Despite these differences, all three gases can feed into overlapping kinase pathways, mitochondrial quality-control networks, and cytoprotective gene programs. A second goal of this review is to move beyond single-gas narratives. We discuss the extent to which gas-gas crosstalk, especially between NO and H2S and the buffering role proposed for H2 under severe oxidative stress, may create systems-level convergence rather than simple additive antioxidant effects. We argue that the most productive conceptual model is not "one gas, one target", but a context-dependent gas signaling network centered on Nrf2/Keap1, mitochondrial adaptation, and thiol chemistry. Finally, we assess the translational implications of this framework across ischemia-reperfusion injury, neurodegeneration, metabolic disease, and aging. We highlight the practical constraints that still limit clinical implementation, including dose windows, burst release, tissue targeting, biomarker selection, and the difficulty of tracking reversible cysteine modifications in vivo. By placing NO, H2S, and H2 into one comparative redox framework, this review aims to clarify what is established, what remains inferential, and where future combination strategies may realistically emerge.