Supraphysiological Citrate Exposure Drives Nonmonotonic Immunometabolic Reprogramming and Proinflammatory Activation...

Patients receiving continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA) frequently experience systemic citrate accumulation, yet its immunometabolic consequences remain poorly understood. Here, we examined how supraphysiological citrate shapes macrophage inflammatory responses using isotope tracing, targeted metabolomics, and in vitro and in vivo inflammatory models. In LPS-stimulated THP-1 cells, U-¹³C-citrate was preferentially retained in proximal citrate-associated metabolite pools, with robust labeling of citrate, cis-aconitate, and itaconate, but minimal labeling of downstream tricarboxylic acid (TCA)-related or glycolytic intermediates. Citrate exposure also increased proximal citrate-related metabolite pools, while acetyl-CoA levels were more strongly increased at 1 mM than at 6 mM. U-¹³C-glucose tracing further showed that citrate exposure redistributed glucose-derived carbon, increasing its retention in glycolysis- and pentose phosphate pathway-related intermediates while reducing its relative contribution to proximal TCA-related metabolites. Consistent with this, citrate increased extracellular acidification rate and upregulated GLUT1 and PKM2. In THP-1 cells, PBMCs, and BMDMs, citrate amplified LPS-induced cytokine production in a nonmonotonic manner, with 1 mM generally producing a stronger proinflammatory effect than 6 mM. In vivo, citrate administration exacerbated hypercytokinemia and increased M1 macrophage polarization in LPS-treated mice. Moreover, citrate-induced proinflammatory responses were attenuated by inhibition of glycolysis, citrate-to-acetyl-CoA conversion, or histone acetylation. Collectively, supraphysiological citrate promotes monocyte/macrophage proinflammatory activation through metabolic and epigenetic reprogramming, with a nonlinear dose response. These findings suggest that systemic citrate accumulation during CRRT may aggravate inflammatory tissue or organ injury and should be considered carefully in inflammatory settings.