Effect of p-cresyl sulfate in cardiorenal axis in mice

Abstract BACKGROUND AND AIMS Uremic toxins (UT) are extremely relevant for the understanding of pathologies of the cardiovascular system once kidney and heart have a close relationship and share different functions. UT are divided into three groups according to physicochemical characteristics: small water-soluble compounds, medium compounds, and protein-bound uremic toxins (PBUT). The PBUT are cytotoxic molecules that have shown deleterious effects in various tissues, including the cardiovascular system. P-Cresyl (PCS), a toxin derived from tyrosine, is one of most important UT once it has a strong affinity for serum proteins, which makes their removal by dialysis difficult. Although some deleterious effects of PCS are known, systematic studies that address the cellular and molecular mechanisms of action of PCS, in the kidney and heart, are still scarce [1, 2]. Moreover, many works in the literature diverge as to the experimental model and the dose of PCS to be used. In this sense, the present study aimed define the dose of PCS capable of leading to renal impairment in mice and also evaluate the effect of PCS alone (without renal injury installed) in kidney and heart. METHODS C57BL/6J male mice 6–8 weeks old (22–28 g) were obtained from the Animal Facility of Federal University of ABC (SP, Brazil). All procedures and protocols were approved by the Ethics Committee on Animal Use of the Federal University of ABC (no. 6 548 291 020). A dose response curve was performed, and the mice were divided into four groups and treated for 21 days, i.p.: Vehicle (saline), PCS 60 mg/L, PCS 40 mg/L and 20 mg/L. Doses were based on uremic maximum concentration available on EUTox-European Uremic Toxins Work Group [3]. After treatment, kidneys, heart, blood, tibia were collected to morphometric and biochemical analysis. Gene expression was evaluated using real-time PCR. RESULTS The EUTox suggested that ∼40 mg/L is the maximum uremic dose for humans. However, the dose–response curve showed that only PCS 20 mg/L was able to increase the mRNA levels of renal injury markers such as Cystatin (3x), KIM-1 (6x) and Vimentin (12x) in relation to control animals (P < .05). Besides, it was possible to observe a decrease on mRNA gene expression of IL-1β levels in kidney (40%, P < .05) when compared with control group. No alterations were observed in MCP-1 levels. In relation to cardiac changes, heart weight/tibia length ratio, showed a cardiac atrophy about 13% after PCS treatment. The OAT 1 and 3 expression did not alter after different doses of PCS treatment. CONCLUSION The results indicated that lowest dose of PCS was able to promote renal injury and cardiac remodeling, despite the changes in OAT1 and OAT3 in kidney and heart. In addition, the establishment of critical dose in mice model is very important since the use of knockout mice models could help to understand the role of UT in organ–organ crosstalk. Finally, this study indicates that the PCS has an impact in kidney/heart axis independent of previous renal injury. The molecular mechanisms involved in cardiac atrophy and inflammatory status are being investigated by our group.