HRH1 and diabetic kidney disease: Histamine exerts pro-fibrotic and pro-inflammatory effects through these receptors during the development of DKD, wherein the inhibition of H1R can maintain the integrated morphology of podocytes (Veglia et al., 2016), whereas inhibition of H4R can attenuate the reabsorptive dysfunction in proximal tubules in STZ-induced DKD (Pini et al., 2018).