Indoxyl Sulfate Contributes to Progression of Renal Injury in the Postpartum Period Following Pregnancy-Related Acute Kidney Injury

Pregnancy-related acute kidney injury (PR-AKI) increases the risk of chronic kidney disease (CKD) in the postpartum period, yet mechanisms driving this transition remain unclear. Uremic toxins, including indoxyl sulfate (IS), are implicated in AKI-to-CKD progression. Using a rat model of PR-AKI induced by ischemia–reperfusion on gestational day (GD) 18, we assessed IS contributions to renal injury in the postpartum. A subset of rats received the oral adsorbent AST-120 in the postpartum period to reduce IS. Additional groups received IS during pregnancy with or without AST-120 treatment in the postpartum period. Renal function, blood pressure, circulating and urinary IS concentrations, and renal histopathology were evaluated. PR-AKI resulted in sustained postpartum elevations in circulating (p = 0.03) and urinary (p < 0.03) IS, reduced urine output (p = 0.03), increased proteinuria (p < 0.0001), increased serum albumin, and increased renal fibrosis (p = 0.008) compared to normal pregnant control rats. Absorption of indole, a precursor for IS, significantly reduced urinary IS (p = 0.03), reduced serum creatinine (p = 0.006), and attenuated renal fibrosis (p = 0.002) in treated PR-AKI rats. While not significant, indole absorption improved urine output (p = 0.06) and reduced proteinuria (p = 0.07) in treated PR-AKI rats. IS administration during pregnancy recapitulated key features of postpartum CKD. Elevated IS contributes to persistent renal injury following PR-AKI. Postpartum reduction in IS with AST-120 dampens the progression of renal injury. These findings highlight uremic toxins as mechanistic drivers and potential therapeutic targets in post partum CKD following PR-AKI.