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Additional file 1: Figure S1. Intraperitoneal administration of famotidine did not significantly alter IL-1β or CXCL1 levels at 2.5 or 6 h post LPS exposure. A–D Male C57BL/6 mice, 8–12 weeks of age, were injected with LPS (7 mg/kg) with or without famotidine (FM, 0.4 or 4 mg/kg, in 100 µl volume), intraperitoneally 30 min before LPS injection. Mice were euthanized 2.5 h after LPS or FM administration. Serum and spleen IL-1β and CXCL1 were measured (N = 10 mice per group), as well as serum IL-6 (N = 5 mice per group). E–H Mice received an IP injection of famotidine or vehicle (0.04 or 0.4 mg/kg, in 5 µl volume) 30 min before LPS injection. LPS was administered IP at 7 mg/kg. Mice were euthanized 6 h post-LPS injection. N = 5 for normal group. N = 13–14 for others. Figure S2. Effects of other histamine 2 receptor antagonists. A–D Male C57BL/6 mice had ICV injection of PBS or tiotidine (0.04 or 0.4 mg/kg in 5 µl volume) 30 min before LPS. LPS was administered IP at 7 mg/kg. Mice were euthanized 2.5 h post-LPS injection and levels of serum and spleen TNF and IL-6 were measured. N = 5 for normal group. N = 4 for tiotidine 4 mg/kg group and N = 8 for other groups. *P

Additional file 1: Figure S1. ChAT administration decreases SBP and DBP. A Change in normalized SBP in the 3 h period after ChAT administration. SBP is normalized to the 30-min period before ChAT or vehicle administration. After normalization, area under the curve is calculated from a baseline of 100%. Negative values correspond to decrease in SBP. n = 7–11. *p

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The cytokine macrophage migration inhibitory factor (MIF) possesses unique tautomerase enzymatic activity, which contributes to the biological functional activity of MIF. In this study, we investigated the effects of blocking the hydrophobic active site of thet automerase activity of MIF in the pathogenesis of lung cancer. To address this, we initially established a Lewis lung carcinoma (LLC) murine model in Mif-KO and wild-type (WT) mice and compared tumor growth in a knock-in mouse model expressing a mutant MIF lacking enzymatic activity (Mif P1G). Primary tumor growth was significantly attenuated in both Mif-KO and Mif P1G mice compared with WT mice. We subsequently undertook a structure-based, virtual screen to identify putative small molecular weight inhibitors specific for the tautomerase enzymatic active site of MIF. From primary and secondary screens, the inhibitor SCD-19 was identified, which significantly attenuated the tautomerase enzymatic activity of MIF in vitro and in biological functional screens.In the LLC murine model, SCD-19, given intraperitoneally at the time of tumor inoculation, was found to significantly reduce primary tumor volume by 90% (p < 0.001) compared with the control treatment. To better replicate the human disease scenario,SCD-19 was given when the tumor was palpable (at d 7 after tumor inoculation) and, again, treatment was found to significantly reduce tumor volume by 81% (p < 0.001) compared with the control treatment. In this report, we identify a novel inhibitor that blocks the hydrophobic pocket of MIF, which houses its specific tautomerase enzymatic activity, and demonstrate that target ingthis unique active site significantly attenuates lung cancer growth in in vitro and in vivo systems. Refereed/Peer-reviewed

Background. Severe COVID-19 is characterized by pro-inflammatory cytokine release syndrome (cytokine storm) which causes high morbidity and mortality. Recent observational and clinical studies suggest famotidine, a histamine 2 receptor (H2R) antagonist widely used to treat gastroesophageal reflux disease , attenuates the clinical course of COVID-19. Because evidence is lacking for a direct antiviral activity of famotidine, a proposed mechanism of action is blocking the effects of histamine released by mast cells. Here we hypothesized that famotidine activates the inflammatory reflex, a brain-integrated vagus nerve mechanism which inhibits inflammation via alpha 7 nicotinic acetylcholine receptor ( α7nAChR ) signal transduction, to prevent cytokine storm. Methods. The potential anti-inflammatory effects of famotidine and other H2R antagonists was assessed in mice exposed to lipopolysaccharide (LPS)-induced cytokine storm. As the inflammatory reflex is integrated and can be stimulated in the brain, and H2R antagonists penetrate the blood brain barrier poorly, famotidine was administered by intracerebroventricular (ICV) or intraperitoneal (IP) routes. Results. Famotidine administered IP significantly reduced serum and splenic LPS-stimulated tumor necrosis factor α and interleukin-6 concentrations, significantly improving survival. The effects of ICV famotidine were significantly more potent as compared to the peripheral route. Mice lacking mast cells by genetic deletion also responded to famotidine, indicating the anti-inflammatory effects are not mast cell dependent. Either bilateral sub-diaphragmatic vagotomy or genetic knock-out of α7nAChR abolished the anti-inflammatory effects of famotidine, indicating the inflammatory reflex as famotidine's mechanism of action. While the structurally similar H2R antagonist tiotidine displayed equivalent anti-inflammatory activity, the H2R antagonists cimetidine or ranitidine were ineffective even at very high dosages. Conclusions. These observations reveal a previously unidentified vagus nerve-dependent anti-inflammatory effect of famotidine in the setting of cytokine storm which is not replicated by high dosages of other H2R antagonists in clinical use. Because famotidine is more potent when administered intrathecally, these findings are also consistent with a primarily central nervous system mechanism of action.