Lactic Acid Suppresses IL-33–Mediated Mast Cell Inflammatory Responses via Hypoxia-Inducible Factor-1α–Dependent miR-155 Suppression

Abstract

Lactic acid (LA) is present in tumors, asthma, and wound healing, environments with elevated IL-33 and mast cell infiltration. While IL-33 is a potent mast cell activator, how LA affects IL-33-mediated mast cell function is unknown. To investigate this, mouse bone marrow-derived mast cells (BMMC) were cultured with or without LA and activated with IL-33. LA reduced IL-33-mediated cytokine and chemokine production. Using inhibitors for monocarboxylate transporters (MCT) or replacing LA with sodium lactate revealed that LA effects are MCT-1- and pH-dependent. LA selectively altered IL-33 signaling, suppressing TAK1, JNK, ERK, and NFκB phosphorylation, but not p38 phosphorylation. LA effects in other contexts have been linked to HIF-1α, which was enhanced in BMMC treated with LA. Since HIF-1α has been shown to regulate the microRNA miR-155 in other systems, LA effects on miR-155-5p and -3p species were measured. In fact, LA selectively suppressed miR-155-5p in a HIF-1α-dependent manner. Moreover, overexpressing miR-155-5p, but not miR-155-3p, abolished LA effects on IL-33-induced cytokine production. These in vitro effects of reducing cytokines were consistent in vivo, since LA injected intraperitoneally into C57BL/6 mice suppressed IL-33-induced plasma cytokine levels. Lastly, IL-33 effects on primary human mast cells were suppressed by LA in an MCT-dependent manner. Our data demonstrate that LA, present in inflammatory and malignant microenvironments, can alter mast cell behavior to suppress inflammation.

Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IL-33-induced cytokine production in primary mouse mast cells

“…Bone marrow derived mast cells (BMMC) were differentiated in IL-3-containing supernatant from WEHI-3 cells and SCF-containing supernatant from BHK-MKL cells as described to yield ≥ 90% FcεRI + and cKit + mast cells at 21 days [16]. Peritoneal lavage cells were cultured in complete RPMI containing 10% FBS and IL-3+SCF (10 ng/mL) for 7–10 days to yield ~85% FcεRI + and cKit + mast cells.…”

Mast cells signal their importance in health and disease

“…One can speculate that the balance between the proinflammatory and anti-inflammatory roles of mast cells might be regulated by additional microenvironmental cues, depending on the pathophysiologic situation. For example, production of lactic acid, 76 a byproduct of anaerobic glycolysis present in pathologic environments that promote IL-33 production (inflammation, wound healing, and tumors) and TGF-b1, 77 levels of which are increased in patients with chronic inflammatory conditions and certain allergic diseases, markedly reduced IL-33-mediated mast cell inflammatory responses.…”

Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IgE-mediated mast cell activation through attenuation of NFκB and AP-1 transcription

“…Most experiments were conducted using mouse bone marrow-derived mast cells (BMMC), which were derived by culture for at least 21 days in complete RPMI supplemented as previously described, with ≥90% FceRI + and cKit + mast cells present by day 21 [19–21]. Cultures were used for up to 8 weeks of age and age-matched in experiments.…”