RESUMO
Listeriosis, caused by Listeria monocytogenes (L.m.), poses a significant public health concern as one of the most severe foodborne diseases. The pathogenesis of L.m. involves critical steps such as phagosome rupture and escape upon internalization. Throughout infection, L.m. influences various host processes, including lipid metabolism pathways, yet the role of lipid droplets (LDs) remains unclear. Here, we reported a rapid, time-dependent increase in LD formation in macrophages induced by L.m. LD biogenesis was found to be dependent on L.m. viability and virulence genes, particularly on the activity of the pore-forming protein listeriolysin O (LLO). The prevention of LD formation by inhibiting diacylglycerol O-acyltransferase 1 (DGAT1) and cytosolic phospholipase A2 (cPLA2) significantly reduced intracellular bacterial survival, impaired prostaglandin E2 (PGE2) synthesis, and decreased IL-10 production. Additionally, inhibiting LD formation led to increased levels of TNF-α and IFN-ß. Collectively, our data suggest a role for LDs in promoting L.m. cell survival and evasion within macrophages.
RESUMO
Background & Aims: Lipid droplet (LD) accumulation in cells and tissues is understood to be an evolutionarily conserved tissue tolerance mechanism to prevent lipotoxicity caused by excess lipids; however, the presence of excess LDs has been associated with numerous diseases. Sepsis triggers the reprogramming of lipid metabolism and LD accumulation in cells and tissues, including the liver. The functions and consequences of sepsis-triggered liver LD accumulation are not well known. Methods: Experimental sepsis was induced by CLP (caecal ligation and puncture) in mice. Markers of hepatic steatosis, liver injury, hepatic oxidative stress, and inflammation were analysed using a combination of functional, imaging, lipidomic, protein expression and immune-enzymatic assays. To prevent LD formation, mice were treated orally with A922500, a pharmacological inhibitor of DGAT1. Results: We identified that liver LD overload correlates with liver injury and sepsis severity. Moreover, the progression of steatosis from 24 h to 48 h post-CLP occurs in parallel with increased cytokine expression, inflammatory cell recruitment and oxidative stress. Lipidomic analysis of purified LDs demonstrated that sepsis leads LDs to harbour increased amounts of unsaturated fatty acids, mostly 18:1 and 18:2. An increased content of lipoperoxides within LDs was also observed. Conversely, the impairment of LD formation by inhibition of the DGAT1 enzyme reduces levels of hepatic inflammation and lipid peroxidation markers and ameliorates sepsis-induced liver injury. Conclusions: Our results indicate that sepsis triggers lipid metabolism alterations that culminate in increased liver LD accumulation. Increased LDs are associated with disease severity and liver injury. Moreover, inhibition of LD accumulation decreased the production of inflammatory mediators and lipid peroxidation while improving tissue function, suggesting that LDs contribute to the pathogenesis of liver injury triggered by sepsis. Impact and Implications: Sepsis is a complex life-threatening syndrome caused by dysregulated inflammatory and metabolic host responses to infection. The observation that lipid droplets may contribute to sepsis-associated organ injury by amplifying lipid peroxidation and inflammation provides a rationale for therapeutically targeting lipid droplets and lipid metabolism in sepsis.