Modifications of IL-6 by Hypochlorous Acids: Effects on Receptor Binding

Abstract

Interleukin-6 (IL-6) has been implicated in the pathogenesis of inflammatory events including those seen with COVID-19 patients. Positive clinical responses to monoclonal antibodies directed against IL-6 receptors (IL-6Rs) suggest that interference with IL-6-dependent activation of pro-inflammatory pathways offers a useful approach to therapy. We exposed IL-6 to hypochlorous acid (HOCl) in vitro at concentrations reported to develop in vivo . After HOCl treatment, binding of IL-6 to IL-6R was reduced in a dose-dependent manner using a bioassay with human cells engineered to provide a luminescence response to signal transduction upon receptor activation. Similar results followed the exposure of IL-6 to N -chlorotaurine (NCT) and hypobromous acid (HOBr), two other reactive species produced in vivo . SDS-PAGE analysis of HOCl-treated IL-6 showed little to no fragmentation or aggregation up to 1.75 mM HOCl, suggesting that the modifications induced at concentrations below 1.75 mM took place on the intact protein. Mass spectrometry of trypsin-digested fragments identified oxidative changes to two amino acid residues, methionine 161 and tryptophan 157, both of which have been implicated in receptor binding of the cytokine. Our findings suggest that exogenous HOCl and NCT might bring about beneficial effects in the treatment of COVID-19. Further studies on how HOCl and HOBr and their halogenated amine derivatives interact with IL-6 and related cytokines in vivo may open up alternative therapeutic interventions with these compounds in COVID-19 and other hyperinflammatory diseases.

Systemic Administration of Neutral Electrolyzed Saline as a Novel Treatment for Rheumatoid Arthritis Reduces Mechanical and Inflammatory Damage to the Joints: Preclinical Evaluation in Mice

“…In that sense, and according to the findings in the animal model of this study, the administration of NES was beneficial in modulating IL-6 levels, which correlated with a reduction in joint damage, especially for the group treated with the highest dose of NES (NES40). Furthermore, a recent in vitro report showed that hypochlorous acid (HOCl), one of the main components of NES, is capable of interacting with IL-6, blocking or reducing interaction with its receptors in a dose-dependent manner [ 29 ], although more studies are needed in this regard.…”

Antimicrobial efficacy, mode of action and in vivo use of hypochlorous acid (HOCl) for prevention or therapeutic support of infections

“…By inactivating interleukin 6 (IL6), HOCl possibly downregulates mediators of the ‘cytokine storm’ that characterizes clinical deterioration in specific diseases (e.g., COVID-19) [ 48 ], [ 52 ], [ 53 ]. Based on their in vitro studies on the deactivation of IL-6 by HOCl at concentrations reported to develop in vivo , Robins et al [ 54 ] suggest that exogenous HOCl and NCT might bring about beneficial effects in the treatment of COVID-19. Their results and further studies on how HOCl and HOBr and their halogenated amine derivates interact with IL-6 may open alternative therapeutic interventions in COVID-19 and other hyperinflammatory diseases.…”

Hypochlorous Acid: From Innate Immune Factor and Environmental Toxicant to Chemopreventive Agent Targeting Solar UV-Induced Skin Cancer

“…IL-6, IKK) and mediators of tissue remodeling (e.g. MMP7, TIMP-1), causing effects that are mostly consistent with modulation, attenuation, and resolution of inflammatory tissue responses (35,(80)(81)(82)(83)(84)(85)(86)(87)(88)(89). Specifically, inactivation of IKK (inhibitor of IkB kinase) through oxidation (Cys114/115) is thought to cause the hypochlorite-dependent attenuation of psoriasis observable upon topical application (35).…”

“…Importantly, N-chlorotaurine formation may cause the negative regulation of inflammatory processes by multiple distinct molecular mechanisms attenuating NF-kB and related cytokine signaling (88,116). Interestingly, taurine might not only attenuate direct chemical reactivity of HOCl through sacrificial quenching, but chloro-taurine may then act as a redox-directed signaling modulator of major inflammatory targets and pathways.…”

“…modification of inflammatory factors, such as IL-6 and NFkB. Indeed, N-chlorotaurine exposure of IL-6 causes oxidation of residues relevant to IL6R receptor-binding (Met161 and Trp157) (88). Negative modulation of NF-kB by N-chlorotaurine (and other chloramines such as glycine chloramine) is thought to originate from oxidation of Met45 in IkB (preventing its ubiquitination and proteasomal degradation) (116,117).…”