The Summarized Assessment of Endothelin A Receptor Expression in Renal Transplant Compartments Associated with Antibody-Mediated Rejection

The occurrence of anti-endothelin A receptor antibodies may be useful in diagnosis of transplant damage. We noticed that the presence of the endothelin A receptor (ETA receptor) in biopsy compartments is yet to be defined. We decided therefore to analysed the presence and relevance of the ETA receptor in biopsy to define the cause. Our study aims to evaluate the expression of ETA receptors in renal recipients after a biopsy due to the worsening of transplant function. Methods: The expression of ETA receptors was analyzed in renal transplant biopsies using the immunohistochemical method. The evaluation of ETA receptors was performed on paraffin sections. ETA receptor expression was analyzed in four compartments of renal transplant biopsies: glomeruli; vessels; tubular epithelium; and interstitium. The assessment was presented using a three-step scale (0: lack of expression; 1: mild to moderate immunoreactivity; 2: high expression). The results of each compartment from a single biopsy were summarized and assessed in the context of antibody-mediated rejection (AMR). Results: We analyzed 156 patients who had a renal allograft biopsy after renal transplantation. For each patient, we created a summarized ETA receptor expression score. The summarized ETA receptor expression score analysis showed statistically significant differences in patients with and without AMR. In addition, we noticed that patients with AMR had a significantly higher mean summarized expression of ETA receptor score of 3.28 ± 1.56 compared to patients who had a biopsy for other reasons with a mean summarized ETA receptor expression score of 1.47 ± 1.35 (p < 0.000001). ROC analysis of the ETA receptor expression score for detecting AMR status showed that the most appropriate cut-off for the test of the chosen binary classifier is between 2 and 3 of the summarized ETA receptor expression score. Conclusions: The expression of endothelin A receptors in renal transplant compartments may be associated with antibody-mediated rejection. The positive ETA receptor staining might be a vital feature in the diagnosis of damage in AMR. The summarized ETA receptor expression score seems to be an exciting diagnostic tool in transplant injury assessment.

FC 088DUAL BLOCKADE OF ENDOTHELIN A RECEPTOR (ETA) AND SODIUM-GLUCOSE COTRANSPORTER 2 (SGLT2) TO PREVENT DIABETIC KIDNEY DISEASE PROGRESSION ON A TYPE 2 MURINE MODEL

Background and Aims Sodium-glucose cotransporter 2 inhibitors (SGLT2i) and endothelin A receptor (ETA) antagonist have shown nephroprotective effects in diabetic kidney disease (DKD) through blood pressure and urinary albumin loss reduction. The protective impact and the pathways through which they exert this protection have not yet been elucidated. This study aimed to investigate the effects of the add-on therapy of SGLT2i and ETA antagonists on a type 2 diabetes murine model. Method 12 weeks-old db/db mice were treated for 8 weeks with different combinations of empagliflozin 10 mg/Kg/day (SGLT2i), atrasentan 7 mg/Kg/day (ETA antagonist) or ramipril 8 mg/Kg/day. A group of non-diabetic mice (db/m) was included as negative control. In vivo variables were recorded during treatment, including transdermal measured glomerular filtration rate (GFR) and urinary albumin-to-creatinine ratio (UACR). After treatment kidneys were preserved for histopathological studies. Results After 8 weeks of treatment empagliflozin decreased fasting blood glucose alone or in combination with atrasentan or ramipril (234.2 mg/dL mean reduction in three treated groups when compared to db/db). Ramipril decreased blood pressure (BP) in monotherapy or in add-on therapy. Empagliflozin or atrasentan alone did not have any effect on blood pressure, but combination of atrasentan and ramipril had a synergistic effect and reduced both systolic (9.0 mmHg, CI 95%: -16.3 to -1.1; P=0.028) and diastolic BP (11.9 mmHg, CI 95%: -17.7 to -3.1; P=0.005) when compared to ramipril alone. The combination of atrasentan and ramipril significantly reduced UACR (1002 ug/mg, CI 95%: -2312.0 to -32.4; P=0.043). Empagliflozin treatment alone or in combination also reduced UACR (686.0 ug/mg mean reduction in three treated groups), although this reduction was not statistically significant. In the kidney, empagliflozin in monotherapy or combination reduced glomerular mesangial matrix expansion (4.85% mean mesangial reduction in three treated groups). Treatments with atrasentan and ramipril also reduced measangial matrix expansion. Conclusion Both empagliflozin and atrasentan demonstrated possible beneficial effects in DKD by reducing BP, UACR, and mesangial matrix expansion. The add-on therapy did not show greater protective effects in the analysed variables. Further studies are needed to characterize these protective effects and pathways involved.

Treatment With Endothelin-A Receptor Antagonist BQ123 Attenuates Acute Inflammation in Mice Through T-Cell-Dependent Polymorphonuclear Myeloid-Derived Suppressor Cell Activation

The endothelin-A receptor antagonist BQ123 is an effective treatment agent for hypertension and obese cardiomyopathy. However, the role of BQ123 in controlling acute inflammatory diseases and its underlying mechanisms are not well understood. Here, we showed that BQ123 activated polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in mice and that the IL13/STAT6/Arg1 signaling pathway is involved in this process. Importantly, both treatment with BQ123 and the transfer of BQ123-induced PMN-MDSCs (BQ123-MDSCs) were effective in relieving inflammation, including dextran sulfate sodium (DSS)-induced colitis, papain-induced pneumonia, and concanavalin A (ConA)-induced hepatitis, in mice. The treatment effects were mediated by the attenuation of the inflammation associated with the accumulation of PMN-MDSCs in the colon, lung, and liver. However, concurrent injection of Gr1 agonistic antibody with BQ123 induced PMN-MDSC aggravated the observed acute inflammation. Interestingly, no remission of inflammation was observed in Rag2 knockout mice administered BQ123-MDSCs, but co-injection with CD3+ T cells significantly relieved acute inflammation. In summary, BQ123-induced PMN-MDSCs attenuated acute inflammation in a T cell-dependent manner, providing a novel potential strategy to prevent the occurrence of acute inflammation.

Endothelin A Receptors Expressed in Glomeruli of Renal Transplant Patients May Be Associated with Antibody-Mediated Rejection

Background: Non-human leukocyte antigen (HLA) anti-endothelin A receptor antibodies are presented as being potentially important, but the expression of the endothelin A receptor in glomeruli (ETA receptor (g+)) has not yet been described. We decided to evaluate the presence and relevance of the ETA receptor in for-cause renal transplant biopsies. The aim of our study was to evaluate the immunoreactivity of the ETA receptor and its significance in patients who underwent a renal transplant biopsy due to the deterioration of transplant function, with detailed characterization of staining in glomeruli. Methods: The immunohistochemical expression of ETA receptor (ETAR) was analyzed in renal transplant biopsies. Microscopic evaluation was performed on paraffin sections in glomeruli. The analysis was performed using a two-step scale (0: lack of ETAR expression; 1: the presence of ETAR expression—mild to moderate immunoreactivity). Results: We analyzed 149 patients who underwent renal allograft biopsy after renal transplantation. Positive staining of ETA receptors in glomeruli (ETA receptor (g+)) was noticed in 13/149 (8.7%) patients. Five of these 13 (38.5%) patients with ETA receptor (g+) developed antibody-mediated rejection (AMR), while 13 of the remaining 136 (9.5%) ETA receptor (g-) patients developed AMR (p = 0.0022). Graft loss was noticed in all but one ETA receptor (g+) patient with AMR (4/5; 80%), but only in 2/13 (15%) ETA receptor (g-) patients with AMR (p = 0.009) during the first year after biopsy. Conclusions: The expression of endothelin A receptors in glomeruli seems to be a potentially important feature in the diagnosis of damage during antibody-mediated rejection. It may help to identify patients at a higher risk of allograft rejection and injury.