A proline-rich polypeptide complex (PRP) influences inducible nitric oxide synthase in mice at the protein level

A proline-rich polypeptide complex (PRP) with immunoregulatory and procognitive properties showed a beneficial effect in Alzheimer’s disease (AD) when administered orally in the form of Colostrinin® tablets. The mechanism of action of PRP/Colostrinin in AD has not been yet clarified. It is known that oxidative stress enhances neurodegenerative processes. It was previously shown that the PRP regulates the secretion of cytokines and inhibits NO and O2− release in cell cultures. Since the results on isolated cells or cell lines frequently do not reflect events in vivo, the effect of PRP on NO release and iNOS protein synthesis in mice treated with LPS was studied. The PRP did not induce the production of NO. However, in the presence of PRP applied 6 h after LPS, about 40% inhibition of NO release was observed. This effect was accompanied by lower iNOS protein expression in peritoneal cells. In the liver sections of mice treated with PRP 6 h after LPS application, the number of iNOS-positive cells was significantly reduced. These results indicate that PRP can act as a regulator of inflammatory processes. The inhibition of iNOS activity/expression could be one of the mechanisms of the therapeutic effect of PRP/Colostrinin in AD.