Role of Nrf2-antioxidant in radioprotection by root extract of Inula racemosa.

Purpose:Inula racemosa, a Trans-Himalayan plant is an important medicinal herb. In this study, the radio-modulatory efficacy of aqueous root extract of I. racemosa was investigated. Materials and methods: Normal Kidney Epithelium cells were treated with extract (50-200 µg/ml) and exposed to 3 Gy of γ-radiation, while C57BL/6 mice were administered with extract (300-600 mg/kg BW) intraperitoneally prior to exposure to 7.5 Gy of γ-radiation to assess radiation modulatory efficacy. Results: The administration of extract (30 min and 1 h) prior to radiation exposure improved the survival of NKE cells (as measured by proliferation), restored MMP and ROS levels as compared to radiation-exposed alone cells. These cells showed up-regulated Nrf2 protein levels at 7 h and increased expression of HO-1 and NOQ1 protein at 24 h In mice, the 30 days whole body survival study demonstrated that extract pre-treatment increases survival or delays the onset of radiation-induced mortality as against 70% mortality of 7.5 Gy of γ-radiation. Conclusions: The aqueous extract of roots of I. racemosa enhanced the survival of irradiated NKE cells and rescued C57BL/6 mice against WBI-induced mortality. The radiation modulation efficacy was mediated through cumulative activation of HO-1 and NQO1 downstream of Nrf2 translocation in NKE cells. Abbreviations: ARE: Antioxidant Response Element; FITC: Fluorescein isothiocyanate; GCS: Glutamylcysteine synthase; HO-1: Heme oxygenase-1; LPS: Lipopolysacharide; MRP: Multidrug Resistance-Associated Proteins; NQO1: NAD(P)H Quinone Dehydrogenase 1; NRH: Quinone Oxidoreductase 2 (NQO2); PBS: Phosphate Buffer Saline; PKA: Protein Kinase A; PKC: Protein Kinase C; PI3-kinase: Phosphatidylinositol 3-Kinase; SRB: Sulforhodamine B; UV: Ultra-Violet radiation.

Crosstalk of toll-like receptors signaling and Nrf2 pathway for regulation of inflammation.

Inflammation as a second line of defense of innate immunity plays a crucial role in eliminating invading pathogens (bacteria, viruses, fungi as well as other parasites). The inflammatory response may also activate adaptive immune system involving lymphocytes to mount either antibody dependent or cell-mediated immune responses to clear pathogenic insult. However, if continued, the inflammatory processes may become uncontrolled culminating in cellular injury and tissue destruction, thereby manifesting itself in chronic form. The chronic inflammation has been associated with numerous human pathological conditions like allergies and autoimmune diseases, atherosclerosis, arthritis, Alzheimer's disease, cancer, obesity, type 2 diabetes, schizophrenia, neuro-degenerative diseases and numerous others. The dysregulated inflammatory process is associated with overproduction of free radicals leading to oxidative stress and activation of different cell signaling pathways. The regulation of inflammation by TLR signaling as well as Nrf2 pathways separately is widely documented. Since both these major signaling pathways modulate inflammation, they may crosstalk to bring about coordinated inflammatory responses. The linkage between TLR signaling and Nrf2-Keap1 pathway may serve as a bridge between immune regulation and oxidative stress responses through regulation of inflammation. Also, inflammation is reportedly responsible for the plethora of diseased conditions; a study of its regulation by targeting the TLR-Nrf2 cross-talks may also be beneficial for the development of therapeutic therapies or prophylactic treatments. Hence, present review focuses on the crosstalk between TLR signaling and Nrf2 pathway with respect to their role in modulation of inflammation in normal as well as pathologic conditions.

Phytochemical analysis and differential in vitro cytotoxicity assessment of root extracts of Inula racemosa.

The root of Inula racemosa is known for its antifungal, hypolipdemic and antimicrobial properties in traditional Indian Ayurvedic and Chinese system of medicine. The biological efficacy of Inula species is mainly due to the presence sesquiterpene lactone (Isoalantolactone and Alantolactone), which are reported to be inducers of Nrf2 antioxidant pathway. The investigation of properties and efficacy of root extracts of I. racemosa and their comparison was done with a view to find most efficacious extract for use at cellular level (both normal and transformed). In the present study different extracts of root of I. racemosa (aqueous, ethanolic, and 50% aqueous-ethanolic) were prepared and compared for their antioxidant potential, reducing capacity, polyphenol content and flavonoid content. Our investigations suggested that the aqueous extract possess highest antioxidant capacity and reducing potential. The polyphenol content was found to be highest in aqueous extract in comparison with other two extracts. However, all the three extracts showed less flavonoid content. Further, the preliminary phytochemical screening of all the extracts revealed the presence of terpenoids, phytosterols and glycosides. The TLC profile of ethanolic and 50% aqueous-ethanolic extracts showed the presence of alantolactone while aqueous extracts did not exhibit its strong presence. This warrants the need of more stringent techniques for characterization of aqueous extract in future. The in vitro cell based toxicity assays revealed that the aqueous extract was less toxic to kidneys cells while ethanolic extract was toxic to cells even at low concentrations. Hence, the current investigations showed better efficacy of the aqueous extract with respect to other extracts and found to be promising for its future application at in vitro levels.