Baicalein Protects H9c2 Cardiomyoblasts Against LPS-Induced Inflammatory Injury by Modulating the NF-κB/NLRP3 Inflammasome Pathway and Mitochondrial ROS.

Background: Sepsis-related cardiomyopathy is mainly induced by uncontrolled inflammation and mitochondrial oxidative damage triggered by endotoxins, especially those of Gram-negative bacteria. Lipopolysaccharide (LPS), an endotoxin, activates the Toll-like receptor 4/nuclear factor kappa B (TLR4/NF-κB) signaling pathway and the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, which further activates caspase-1 to process the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18). Chronic activation of this signaling pathway is responsible for mitochondrial damage and loss of membrane potential. Baicalein, a flavonoid derived from the herbal plant Objectives: In this study, we assessed whether baicalein has a protective effect on H9c2 cardiomyoblasts against inflammatory and mitochondrial injury induced by LPS through regulation of inflammatory pathways involving NF-κB, the inflammasome, caspase-1 activity, cytokine expression, and oxidation. Methods: H9c2 cells were pre-exposed to different baicalein concentrations (5 - 20 µM) and, after 1 hour, exposed to 1 µg/mL of LPS. Analysis included cell viability measurements by MTT assay, lactate dehydrogenase (LDH) release, and microscopic evaluation by phase-contrast microscopy. Expression levels of premature Nlrp3, Il1B, Il18, and Casp1 (0 - 4 h) were analyzed by real-time polymerase chain reaction (PCR). Protein levels of inflammasome and NF-κB pathway proteins were evaluated by immunoblot analysis. Activity of caspase-1 and cytokine secretion of IL-1β and IL-18 were evaluated by colorimetry and enzyme-linked immunosorbent assay (ELISA), respectively. Mitochondrial membrane potential (ΔΨm) was evaluated by staining with JC1 dye, and reactive oxygen species (ROS) levels were evaluated by fluorescence with DCFH2DA; N-acetylcysteine (NAC) was used as an antioxidant positive control. Results: LPS strongly elevated the transcription of Nlrp3 and Il1b at 2 hours, in addition to enhancing protein expression of NLRP3, activity of caspase-1, and secretion of IL-1β and IL-18. Underlying these pro-inflammatory responses were mitochondrial depolarization, augmented ROS production, diminished cell survival, and cytotoxicity. Prior administration of baicalein mitigated NF-κB activation, diminished priming of the inflammasome response at both transcriptional and protein levels, and decreased caspase-1 activity and secretion of the cytokines. Moreover, baicalein maintained mitochondrial membrane potential and diminished ROS within the cells, comparable to NAC, and improved cellular viability and morphology. Conclusions: Baicalein confers substantial protection against LPS-induced inflammatory and oxidative damage in H9c2 cardiomyoblasts by concurrently suppressing NF-κB activation, mitigating NLRP3 inflammasome signaling, curbing caspase-1-driven cytokine maturation, and stabilizing mitochondrial function through reduction of ROS. These findings identify baicalein as a promising candidate for targeting the ROS-inflammasome axis in sepsis-associated cardiac dysfunction and related inflammatory cardiac disorders.