Protein Diet Affects Immune Adaptation and Reduces Inflammation in the Colon of Heterogeneous Nuclear Ribonucleoprotein (hnRNPI) Knockout Mice

Abstract Objectives This current study is aimed to investigate effects of protein diet on immune and inflammation responses in colon using an intestinal-epithelial-cells (IECs)-specific Heterogeneous Nuclear Ribonucleoprotein (hnRNPI) Knockout mouse model. We hypothesized that protein diet may be beneficial for the KO mice by maintaining their colon immune functions and reducing inflammation. Methods In this experiment, the wild-type (WT) group includes the hnRNPIflox/+ mice and the hnRNPIflox/flox mice, heterozygotes are the hnRNPIflox/+; VillinCre/+ mice, and the knockout (KO) mice are the hnRNPIflox/flox; VillinCre/+ mice, intestinal epithelial cells only. Both WT and KO mice in CON group were provided a control diet containing 12.57% kcal from protein, while the treatment group was provided with a protein diet containing 25.15% kcal from protein. Quantitative RT-PCR was performed to examine gene expressions, immunohistochemistry staining was performed to examine CD4 + cells and enzyme-linked immunosorbent assay was performed to examine TNF-α concentration in blood circulation. Results 1With protein diet, mRNA expression of pro-inflammatory cytokines and chemokines–IL-6, IL-1β, Cxcl1, and Ccl2–were significantly lowered in both male and female KO mice, comparing to CON. Expression of IL-10, an immunomodulatory cytokine, showed no significant difference among KO mice in male, however, was significantly increased by protein diet in female KO comparing to CON. Protein diet has no effect on expressions of PD1, PDL1, and PDL2 in male KO mice, but significantly decreased expression of PD1 and PDL1 in female KO mice comparing to CON. ELISA results suggest that both male and female KO mice fed with protein diet had significantly lowered the level of TNF-α comparing to those fed with CON diet in blood circulation. Both male and female KO mice fed with protein diet had significantly lowered CD4 positive cells stained comparing to CON. Conclusions In summary, this current study reports that protein diet provides beneficial effects to IECs-specific-hnRNPI knockout mice by downregulating expressions of pro-inflammatory markers in colon. It also regulates PD1 and PDL1 expression, however only in female. Funding Sources This project was supported by the USDA Cooperative State Research, Education and Extension Service, Hatch project numbers # ILLU-971-351 and ILLU-698-369.