2013 · Lucas — Role of the Toll Like receptor (TLR) radical cycle in chronic inflammation: possible treatments targeting the TLR4 pathway
Super-Abstract
Activation of the Toll-like receptor 4 (TLR4) pathway — triggered by environmental factors such as ozone, particulate matter, ionizing radiation, and LPS from bacteria — may underlie a wide spectrum of chronic inflammatory and neuropsychiatric diseases. This review covers a large number of potential therapeutic agents that target TLR4 and the resulting ROS/RNS cycle, including molecular hydrogen as one of the most selective and safe candidates. (Molecular Neurobiology, 2013.)
Commentary
This is a broad immunology and neuroscience review covering TLR4 as a common pathophysiological hub for diseases including asthma, cardiovascular disease, diabetes, obesity, autoimmune disorders, neuroinflammation, depression, chronic fatigue syndrome, and others. The review surveys a large pharmacological landscape — from synthetic anti-LPS peptides to natural compounds (EGCG, shogaol, cinnamon extract) to N-acetylcysteine and melatonin — and includes molecular hydrogen as one candidate that can attenuate TLR4-mediated ROS/RNS production. H₂ is mentioned as one of many potential agents; it is not the central focus of this paper. No original experimental H₂ data are presented — the H₂ mention draws on existing H₂ literature. This is a hypothesis-generating, wide-scope review.
Key quotes
- „Activation of the TLR4 pathways may cause chronic inflammation and increased production of reactive oxygen and nitrogen species (ROS/RNS) and oxidative and nitrosative stress.“ — the TLR4 radical cycle as a shared pathophysiological mechanism
- „activation of the TLR radical (ROS/RNS) cycle is a common pathway underpinning many „civilization“ disorders and that targeting the TLR radical cycle may be an effective method to treat many inflammatory disorders.“ — the central hypothesis of the paper
- „drugs or substances that modify these pathways may prevent or improve the abovementioned diseases.“ — the therapeutic rationale for TLR4 targeting, including H₂
Our assessment
This is a very broad narrative review linking TLR4 immunology to an extensive list of chronic diseases and surveying multiple potential therapeutic agents. Molecular hydrogen is listed as one candidate among many, not as the central subject. The review presents no original H₂ experimental data. Its breadth is also its limitation: the hypothesis that TLR4 radical cycling underlies all listed „civilization diseases“ is ambitious and remains partially speculative. H₂ is positioned plausibly as a ROS/RNS modulator, but no RA- or disease-specific H₂ clinical data are presented. Useful as a mechanistic map, not as clinical evidence for H₂.
Study design
- Type: narrative review · n: n/a (literature survey) · H₂ relevance: one of many candidate agents listed for TLR4/ROS pathway modulation
- Scope: TLR4 biology, environmental triggers (ozone, LPS, particulates, ionizing radiation), disease spectrum (asthma to neuropsychiatric), therapeutic agents including anti-LPS strategies, TLR4 antagonists, natural compounds, N-acetylcysteine, melatonin, molecular hydrogen
Abstract
Activation of the Toll-like receptor 4 (TLR4) complex, a receptor of the innate immune system, may underpin the pathophysiology of many human diseases, including asthma, cardiovascular disorder, diabetes, obesity, metabolic syndrome, autoimmune disorders, neuroinflammatory disorders, schizophrenia, bipolar disorder, autism, clinical depression, chronic fatigue syndrome, alcohol abuse, and toluene inhalation. TLRs are pattern recognition receptors that recognize damage-associated molecular patterns and pathogen-associated molecular patterns, including lipopolysaccharide (LPS) from gram-negative bacteria. Here we focus on the environmental factors, which are known to trigger TLR4, e.g., ozone, atmosphere particulate matter, long-lived reactive oxygen intermediate, pentachlorophenol, ionizing radiation, and toluene. Activation of the TLR4 pathways may cause chronic inflammation and increased production of reactive oxygen and nitrogen species (ROS/RNS) and oxidative and nitrosative stress and therefore TLR-related diseases. This implies that drugs or substances that modify these pathways may prevent or improve the abovementioned diseases. Here we review some of the most promising drugs and agents that have the potential to attenuate TLR-mediated inflammation, e.g., anti-LPS strategies that aim to neutralize LPS (synthetic anti-LPS peptides and recombinant factor C) and TLR4/MyD88 antagonists, including eritoran, CyP, EM-163, epigallocatechin-3-gallate, 6-shogaol, cinnamon extract, N-acetylcysteine, melatonin, and molecular hydrogen. The authors posit that activation of the TLR radical (ROS/RNS) cycle is a common pathway underpinning many "civilization" disorders and that targeting the TLR radical cycle may be an effective method to treat many inflammatory disorders.
Source & links
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