Alleviation of lipopolysaccharide-induced heart inflammation in poultry treated with carnosic acid via the NF-κB and MAPK pathways.

In intensive poultry farming, environmental stress, pathogen infections, and noise can negatively impact growth or cause sudden death, leading to economic losses. The prevalent use of antibiotics as feed additives to prevent diseases in broilers has raised concerns about antibiotic resistance and highlighted the need for safer and more effective alternatives. Carnosic acid (CA), a bioactive compound derived from rosemary, exhibits notable pharmacological properties, including anti-inflammatory and antioxidant effects. This study investigates CA's efficacy in mitigating lipopolysaccharide (LPS)-induced heart inflammation in broilers. Broilers were pretreated with CA at varying doses (20, 40, and 80 mg/kg) for 7 days then exposed to LPS (200 mg/kg) for 24h to induce an inflammatory response. LPS treatment increased the levels of the cardiac damage markers creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) and inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and inducible nitric oxide synthase (iNOS), but these effects were markedly decreased in CA-pretreated poultry. Histopathological analysis indicated that CA mitigated myocardial fiber rupture and inflammatory cell infiltration. Immunohistochemistry showed that CA sustained high expression levels of the protective protein crystallin alpha B (CRYAB), the expression of which was reduced by LPS. Mechanistic studies demonstrated that CA regulates key inflammatory signaling pathways via inhibiting LPS-induced activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) by reducing the phosphorylation of p65 and inhibitor of nuclear factor kappa-B alpha (IκBα). Additionally, CA attenuated mitogen-activated protein kinase (MAPK) pathway activation, as evidenced by decreased phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 in the CA-treated groups compared to the LPS-only groups. These findings suggest that CA exerts a protective effect against LPS-induced cardiac inflammation by enhancing CRYAB expression and modulating the NF-κB and MAPK pathways. Importantly, the findings emphasize CA's potential as a natural feed additive to enhance cardiac health in poultry and present a promising alternative to conventional antibiotics in livestock management. Further research is needed to investigate its broader applications in animal health and other inflammatory conditions.