Platelets, cellular mediators of thrombosis, are activated during sepsis and are increasingly recognized as mediators of the immune response. Platelet activation is significantly increased in sepsis patients compared to ICU control patients. Despite this correlation, the role of activated platelets in contributing to sepsis pathophysiology remains unclear. We previously demonstrated NOD-like receptor protein 3 inflammasome (NLRP3) inflammasome activation in sepsis-induced platelets from cecal-ligation puncture (CLP) rats. Activated platelets were associated with increased pulmonary edema and glomerular injury in CLP vs. SHAM controls. In this study, we investigated whether inhibition of platelet activation would attenuate NLRP3 activation and renal and pulmonary injury in response to CLP. CLP was performed in male and female Sprague Dawley (SD) rats (n = 10/group) to induce abdominal sepsis and SHAM rats served as controls. A subset of CLP animals was treated with Clopidogrel (10 mg/kg/day, CLP + CLOP) to inhibit platelet activation. At 72 h post-CLP, platelet activation and NLRP3 inflammasome assembly were evaluated, IL-1β and IL-18 were measured in plasma, and tissues, renal and pulmonary pathology, and renal function were assessed. Activated platelets were 7.8 ± 3.6% in Sham, 22 ± 6% in CLP and significantly decreased to 14.5 ± 0.6% in CLP + CLOP (n = 8–10/group, p < 0.05). NLRP3 inflammasome assembly was inhibited in platelets of CLP + CLOP animals vs. CLP. Significant increases in plasma and kidney IL-1β and IL-18 in response to CLP were decreased with Clopidogrel treatment. Renal injury, but not lung histology or renal function was improved in CLP + CLOP vs. CLP. These data provide evidence that activated platelets may contribute to sepsis-induced renal injury, possibly via NLRP3 activation in platelets. Platelets may be a therapeutic target to decrease renal injury in septic patients.

Preeclampsia (PE) is characterized by maternal hypertension, fetal growth restriction (FGR), and increased inflammation and populations of cytotoxic NK cells (cNKs) and inflammatory T-Helper 17 cells (TH17s). Both cytotoxic NK cells and TH17 cells are heavily influenced via IL-1β signaling. Caspase 1 activity leads to the release of the inflammatory cytokine IL-1β, which is increased in women with PE. Therefore, we tested the hypothesis that the inhibition of Caspase 1 with VX-765 in rats with reduced uterine perfusion pressure (RUPP) will attenuate PE pathophysiology. On gestation day (GD) 14, timed pregnant Sprague–Dawley rats underwent the RUPP or Sham procedure and were separated into groups that received either vehicle or VX-765 (50 mg/kg/day i.p.). On GD19, MAP was measured via carotid catheter and blood and tissues were collected. Bio-Plex and flow cytometry analysis were performed on placental tissues. Placental IL-1β was increased in the RUPP rats vs. the Sham rats and treatment with VX-765 reduced IL-1β in the RUPP rats. Caspase 1 inhibition reduced placental cNKs and TH17s in RUPP rats compared to vehicle-treated RUPP rats. Increased MAP was observed in RUPP rats compared with Sham rats and was reduced in RUPP + VX-765 rats. Placental reactive oxygen species (ROS) were elevated in RUPP rats compared to Sham rats. VX-765 administration reduced ROS in treated RUPP rats. Caspase 1 inhibition increased the number of live pups, yet had no effect on fetal weight or placental efficiency in the treated groups. In conclusion, Caspase 1 inhibition reduces placental IL-1β, inflammatory TH17 and cNK populations, and reduces MAP in RUPP rats. These data suggest that Caspase 1 is a key contributor to PE pathophysiology. This warrants further investigation of Caspase 1 as a potential therapeutic target to improve maternal outcomes in PE.

Recently, we reported that the early progression of proteinuria in the obese Dahl salt‐sensitive (SS ^LepR mutant) strain was associated with increased renal macrophage infiltration in the absence of hyperglycemia and elevations in arterial pressure. Macrophages (CD68 ⁺ ) can be divided into two distinct phenotypes: M1‐macrophages (pro‐inflammatory; CD68 ⁺ /iNOS ⁺ ), and M2‐macrophages (anti‐inflammatory; CD68 ⁺ /CD163 ⁺ ). M1‐macrophages induce renal inflammation and fibrosis, whereas M2‐macrophages reduce renal inflammation and fibrosis. Moreover, previous studies have demonstrated that interlukin‐25 (IL‐25) converts resting macrophages and M1‐macrophages into M2‐macrophagess. Therefore, the objective of the current study was to examine whether treatment with IL‐25 would reduce the early progression of renal injury in SS ^LepR mutant rats by increasing renal M2‐macrophages. We also investigated the impact of IL‐25 on M2‐macrophage subtypes: M2a (wound healing/anti‐inflammatory; CD68 ⁺ /CD163 ⁺ /TLR1 ^‐ ), M2b (immune mediated/pro‐inflammatory; CD68 ⁺ /iNOS ^‐ /CD86 ⁺ ), M2c (Regulatory/anti‐inflammatory; CD68+/CD163+/TLR1 ⁺ ), and M2d (tumor associated macrophage/pro‐angiogenic; CD68 ⁺ /VEGF ⁺ ). Four week‐old SS _WT and SS ^LepR mutant rats were treated with either vehicle (PBS) or IL‐25 (1µg/day, i.p., every other day) for 4 weeks. While the administration of IL‐25 did not change total renal macrophage infiltration in both SS _WT and SS ^LepR mutant rats, IL‐25 increased M2a‐macrophages by >50% and reduced M1‐macrophage by 60% in the kidneys of SS ^LepR mutant rats. Interestingly, IL‐25 significantly increased the insulin sensitivity without changing plasma glucose, triglyceride and total cholesterol levels in SS ^LepR mutant rats. IL‐25 administration had no effect on the progression of proteinuria or renal histopathology in SS _WT rats. However, in the SS ^LepR mutant strain, proteinuria was markedly reduced during the first 2 weeks of treatment (105±13 vs. 295±45 mg/day, respectively), which was further consistent after 4 weeks of treatment (314±57 vs. 467±55 mg/day, respectively). The kidneys from SS ^LepR mutant rats displayed glomerular injury with increased mesangial expansion and renal fibrosis versus SS _WT rats. Chronic treatment with IL‐25 significantly decreased glomerular injury and renal fibrosis in the SS ^LepR mutant strain. Overall, these data indicate that IL‐25 reduces the early progression of renal injury in SS ^LepR mutant rats by inducing M2a‐macrophages and suppressing M1‐macrophages. Therefore, IL‐25 may be considered a therapeutic target for renal disease associated with obesity.