Bruijnzeel, A. W. | bioRxiv Science

bioRxiv2026

AB-Free Kava and its Kavalactones Suppress Cigarette Smoke- and Lipopolysaccharide-Induced Lung Inflammation: Efficacy and Mechanisms

Cigarette smoke-induced lung inflammation is a central driver of pulmonary diseases. The limited efficacy of current anti-inflammatory agents underscores the need for structurally novel therapeutics with distinct mechanisms. We recently demonstrated that AB-free kava, a flavokavains A/B-depleted formulation from Piper methysticum containing six major kavalactones, effectively suppresses cigarette smoke-induced lung inflammation in mice. This study aims to identify the bioactive constituent(s) and elucidate underlying mechanisms. These kavalactones revealed a clear structure-activity relationship in suppressing lipopolysaccharide (LPS)-stimulated prostaglandin E2 (PGE2) production in macrophages with desmethoxyyangonin (DMY) as the most potent kavalactone whereas dihydrokavain (DHK, a structurally similar analog) with minimal activity. DMY also effectively reduced LPS-induced interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-) production while DHK was ineffective. Mechanistically, DMY, but not DHK, attenuated COX-2 induction and reduced phosphorylation of cAMP response element-binding protein (CREB). Pharmacological inhibition of protein kinase A (PKA) similarly reduced p-CREB, COX-2 and PGE2, supporting a PKA-dependent CREB/COX-2 signaling in mediating PGE2 suppression while these effects were independent of nuclear factor kappa B (NF-{kappa}B) and activator protein 1 (AP-1) signaling. Similar results were observed for DMY and DHK in attenuating cigarette smoke condensate-induced proinflammatory pathways and PGE2 production. Consistently, DMY demonstrated significant in vivo efficacy in suppressing cigarette smoke-induced lung inflammation while DHK was not effective. Interestingly, dihydromethysticin (DHM) demonstrated the greatest in vivo anti-inflammatory efficacy, although it only exhibited moderate in vitro potency, likely due to its superior bioavailability over DMY. Concordantly, cigarette smoke exposure elevated p-CREB and COX-2 expressions in mouse lungs, which were attenuated by AB-free kava and its bioactive kavalactones with the extent of suppression correlating with their in vivo anti-inflammatory efficacy. DHM effectively suppressed LPS-induced neutrophil accumulation in mouse lungs as well. Collectively, these studies identify bioactive kavalactones in AB-free kava that suppress cigarette smoke- and LPS-induced lung inflammation through the modulation of the PKA/CREB/COX-2 signaling axis, providing a foundation for developing structurally distinct anti-inflammatory agents, particularly targeting smoke-induced inflammation and associated pulmonary diseases.

immunology↗

bioRxiv2026

AB-Free Kava Reduces Anxiety-Like Behavior Without Preventing Nicotine-Induced Exploration Suppression in Mice

Tobacco use is the leading preventable cause of death worldwide. Anxiety increases the risk for smoking, and smoking in turn increases the risk for anxiety disorders. There is therefore a need to identify interventions that reduce anxiety, in general and in the context of smoking, without producing sedation. Kava (Piper methysticum), a natural product with a long history of indigenous use, has been shown to have anxiolytic and calming effects and reduce nicotine withdrawal. The current study examined whether kava without the hepatotoxic flavokavains A and B (AB-free) could reduce anxiety-like behavior in mice repeatedly treated with nicotine. Male and female C57BL/6NCrl mice received either a control diet or an AB-free kava-supplemented diet and underwent two blocks of nicotine treatments. Mice underwent a first block of five every-other-day injections of nicotine (0.5 mg/kg) or saline, with open field testing after each injection, followed one week later by a nicotine challenge. A second block of injections was given using the same injection schedule, followed by a second challenge one week later, and two weeks afterward mice received a final challenge in a novel open field. During the first treatment block, AB-free kava significantly increased center time overall, an effect most pronounced in saline-treated animals, and increased locomotor activity, while nicotine decreased both measures. During the second challenge, nicotine reduced center time but not locomotor activity, and AB-free kava increased center time in saline-treated animals only. During the final challenge, nicotine reduced both measures, whereas AB-free kava increased center time regardless of nicotine treatment, and kava-treated animals also showed a near-significant increase in center entries. These results suggest that AB-free kava reduces anxiety-like behavior without inducing sedation but does not prevent nicotine-induced suppression of exploratory behavior.

pharmacology and toxicology↗