Sulforaphane Pre-Treatment Improves Alveolar Macrophage Killing After Alcohol-Induced Phagocytic Dysfunction In Vitro and in Galleria mellonella Larvae

Background: Alcohol is associated with increased mortality and morbidity globally. Pulmonary infections with opportunistic pathogens can occur in healthy humans; however, binge alcohol intoxication (≥0.08% BAC) is a major risk factor. We have previously shown that a single dose of alcohol comparable to binge alcohol intoxication increases infection by reducing alveolar macrophage function in vivo. Sulforaphane (SFN), a phytonutrient, is a potent inducer of antioxidant production through the induction of nuclear factor erythroid 2-related factor 2 (Nrf2) and inhibition of the nuclear factor kappa-light-chain-enhancer (NF-kB) pathway. The aim of this study was to test the therapeutic potential of SFN given as a pretreatment to prevent alcohol-induced phagocytic dysfunction. Methods: Intracellular phagocytic killing was measured via colony-forming units (CFU) and cytokine expression via ELISA. G. mellonella survival was used to determine the therapeutic potential of SFN in vivo. Results: Dose–response curves indicated that SFN concentrations of less than 20 µM were not cytotoxic in either MH-S (murine) or THP-1 (human) cells. Live infection assay results showed that MH-S and THP-1 cells pretreated with SFN (5 µM) and challenged with 0.2% (v/v) alcohol for 3 or 8 h prior to live B. thailandensis or S. epidermidis infection improved intracellular pathogen killing between 12- and 20-fold compared to macrophages treated with alcohol alone. ELISA analysis indicated that SFN significantly reduced levels of Tumor necrosis factor-alpha (TNF-α) expression at 3 and 8 h compared to controls. Additionally, a Galleria mellonella larvae model demonstrated greater survivability in the prophylaxis group compared to larvae exposed to either Gram-positive or Gram-negative pathogens, as well as in groups that received alcohol prior to pathogen inoculation. Conclusions: Taken together, SFN-induced cytoprotection was extended beyond in vitro cell culture to include an in vivo G. mellonella model demonstrating protection against Gram-positive and negative opportunistic pathogens. These data demonstrate that SFN may be an effective pretreatment option to prevent alcohol-mediated innate immune dysfunction and restore macrophage phagocytic killing.