Recent studies draw attention to how excessive salt (NaCl) intake induces fibrotic alterations in the peritoneum through sodium accumulation and osmotic events. The aim of our study was to better understand the underlying mechanisms. The effects of additional NaCl were investigated on human primary mesothelial cells (HPMC), human primary peritoneal fibroblasts (HPF), endothelial cells (HUVEC), immune cells (PBMC), as well as ex vivo on peritoneal tissue samples. Our results showed that a high-salt environment and the consequently increased osmolarity increase the production of inflammatory cytokines, profibrotic growth factors, and components of the renin–angiotensin–aldosterone system, including IL1B, IL6, MCP1, TGFB1, PDGFB, CTGF, Renin and Ace both in vitro and ex vivo. We also demonstrated that high salt induces mesenchymal transition by decreasing the expression of epithelial marker CDH1 and increasing the expression of mesenchymal marker ACTA2 and SNAIL1 in HPMCs, HUVECs and peritoneal samples. Furthermore, high salt increased extracellular matrix production in HPFs. We demonstrated that excess Na⁺ and the consequently increased osmolarity induce a comprehensive profibrotic response in the peritoneal cells, thereby facilitating the development of peritoneal fibrosis.

Although sepsis-induced acute kidney injury (AKI) is associated with significant morbidity and mortality, its treatment remains unresolved. Oxidative stress and inflammation are key elements in the pathomechanism of AKI. Therefore, in the present study, we investigated the role of DJ-1 protein, known for its antioxidant and anti-inflammatory properties in an animal model of lipopolysaccharide (LPS)-induced AKI. The presence of DJ-1 was detected by immunofluorescence staining in mice kidney samples, human embryonic kidney cells (HEK-293), and peripheral blood mononuclear cells (PBMCs). To investigate DJ-1 functions, Compound-23, a specific DJ-1-binding and preserving compound (CAS: 724737-74-0), was used in vitro and in vivo. Compound-23 reduced the H₂O₂-induced reactive oxygen species (ROS) production of the HEK-293 cells, and their LPS- or H₂O₂-induced death, as well. In accordance, Compound-23 decreased the mRNA expression of the oxidative stress markers NAD(P)H quinone dehydrogenase 1 (NQO1) and glutamate-cysteine ligase (GCLC) in the LPS-treated, and NQO1 in the H₂O₂-treated cells. Moreover, Compound-23 reduced the H₂O₂- and LPS-induced mRNA expression of inflammatory cytokine interleukin 6 (IL6) in both HEK-293 and PBMCs. Using the mice model of LPS-induced AKI, we demonstrated that Compound-23 treatment improved the renal functions of the mice. In addition, Compound-23 decreased the renal mRNA expression of kidney injury molecule 1 (Kim1), neutrophil gelatinase-associated lipocalin (Ngal), Nqo1, Gclc, and Il6 in the LPS-treated mice. Our study revealed that compounds protecting DJ-1 functions may protect the kidney from LPS-induced damage, suggesting that DJ-1 could be a potential drug target for sepsis-induced AKI therapy.