Bioactive compounds in Layacha brown rice (Oryza sativa L.) improve immune responses in mice via activation of transcription factor Nrf2

Dysregulated or weak immunity is caused by ageing, chemo-radiotherapy, COVID-19, infections, steroids, pollutants and toxins. Bioactive foods are required for boosting immunity. In the present study, eight rice (Oryza sativa L.) varieties were selected from the repository of 23,250 Indian germplasm accessions. The immunomodulatory effects of these rice varieties were assessed in vitro and in vivo. Layacha-rice-methanolic-extract (Larimex) significantly enhanced innate (>20%) and adaptive (>10%) immune responses evinced from higher bacterial phagocytosis by macrophages, increased mitogen-induced T-cell proliferation (11%) and scavenged reactive oxygen species (ROS) (70–80%). Larimex activated transcription factor Nrf2 and its downstream genes NQO1, HO1 and Txnrd1 in immune cells. Larimex significantly improved immune responses (>20%) only in cells from wild type but not Nrf2 knock-out mice indicating its causal role in boosting immunity. Untargeted metabolomics of Layacha rice showed preponderance of metabolic pathways and bioactive compounds, which activate Nrf2 in mammalian cells. Layacha rice can be a suitable food for boosting immunity.