Plumbagin Protects Mice from Lethal Sepsis by Modulating Immunometabolism Upstream of PKM2

Abstract

Sepsis is characterized by dysregulated systemic inflammation with release of early (for example, interleukin (IL)-1β) and late (for example, HMGB1) proinflammatory mediators from macrophages. Plumbagin, a medicinal plant-derived naphthoquinone, has been reported to exhibit antiinflammatory activity, but the underling mechanisms remain unclear. Here, we have demonstrated that plumbagin inhibits the inflammatory response through interfering with the immunometabolism pathway in activated macrophages. Remarkably, plumbagin inhibited lipopolysaccharide (LPS)-induced aerobic glycolysis by downregulating the expression of pyruvate kinase M2 (PKM2), a protein kinase responsible for the final and rate-limiting reaction step of the glycolytic pathway. Moreover, the NADPH oxidase 4 (NOX4)-mediated oxidative stress was required for LPS-induced PKM2 expression, because pharmacologic or genetic inhibition of NOX4 by plumbagin or RNA interference limited LPS-induced PKM2 expression, lactate production and subsequent proinflammatory cytokine (IL-1β and HMGB1) release in macrophages. Finally, plumbagin protected mice from lethal endotoxemia and polymicrobial sepsis induced by cecal ligation and puncture. These findings identify a new approach for inhibiting the NOX4/PKM2-dependent immunometabolism pathway in the treatment of sepsis and inflammatory diseases.

SOCS1 is a negative regulator of metabolic reprogramming during sepsis

“…Consistent with this, Yang et al showed that pharmacological inhibition of PKM2 renders mice more resistant to lethal sepsis. This enhanced resistance was associated with reductions in both glycolysis and IL-1β production (22,76). These data, combined with our observations here, suggest that targeting aerobic glycolysis might represent a viable therapeutic strategy for treatment of inflammatory diseases.…”

Endogenous Hydrogen Sulfide Ameliorates NOX4 Induced Oxidative Stress in LPS-Stimulated Macrophages and Mice

“…Nox4 was constitutively active, the elevated Nox4 expression directly translated to increase ROS production [32]. Increasing evidences demonstrated that Nox4 played a detrimental role in process of inflammatory diseases, including sepsis [3,30,33]. Here, our results clearly showed that Nox4 was significantly increased in LPSinduced septic mice, which was accompanied by increased inflammatory mediators and inflammatory cytokines production.…”

“…The NADPH oxidases are a major source of intracellular ROS generation in macrophages [29]. Meanwhile, NADPH oxidase-dependent ROS played a detrimental role in lethal innate immune response in sepsis [4,30]. The role of oxidative stress in septic pathogenesis has been well appreciated [3,4]; however, the mechanisms by which oxidative stress contributed to pathogenesis were not well defined.…”

“…injected with LPS to dectect the CSE expression in main major orgens (A), H 2 S levels (B), lung injury by H&E staining (C), Nox4 expression (D), NADPH oxidase activity (E), ROS production in lungs (F), inflammatory cytokines IL-1β production in plasma (G) ; Data were shown means ± SEM; n=7, # p<0.05, compared with control mice; Cellular Physiology and Biochemistry Cellular Physiology and Biochemistry enhancement played a pivotal role in the regulation of inflammatory responses [30,34]. Pharmacologic or genetic inhibition of Nox4 limited inflammatory response and inflammatory cytokines release [30,35]. Accordingly, lentivirusmediated Nox4 knockdown showed significantly improved survival along with decreased production of inflammatory mediators in LPS-induced sepsis.…”

“…Numerous studies have demonstrated that NADPH oxidase-dependent ROS played a crucial role in the pathophysiology of sepsis by regulating immune cell activation and ending organ injury [29,30]. Previous findings have suggested that many negative effectors are induced by inflammatory stimuli, which then functioned as feedback loops to dampen inflammation or induce endotoxin tolerance [41,42].…”