Perillyl alcohol attenuates rheumatoid arthritis via regulating TLR4/NF-κB and Keap1/Nrf2 signaling pathways: A comprehensive study onin-vitro and in-vivo experimental models.

BACKGROUND: Rheumatoid arthritis is a chronic and idiopathic autoimmune disorder. Perillyl alcohol (POH) is a monoterpene which can be extracted from widely available essential oils and is known for its strong anti-inflammatory and anti-oxidant properties. HYPOTHESIS/PURPOSE: Recent studies have been proven that inhibitors of farnesyltransferase enzyme showed significant anti-arthritic activity. POH is one such natural molecule having anti-inflammatory and anti-oxidant properties by inhibiting farnesyltransferase enzyme which further down regulates NF-κB and Nrf2 via Ras/Raf/MAPK pathway. Also, the effect of POH against rheumatoid arthritis is not known yet. Hence, the present research was intended to assess the anti-arthritic potential of POH in-vitro and in-vivo. METHODS: The in-vitro effects of POH on RAW 264.7 cells stimulated with LPS 1 µg/ml were investigated to its potential therapeutic effects. CFA 100 µl was intradermally administered to rats for the induction of arthritis. POH 100 mg/kg and 200 mg/kg administered topically from day 1 to day 28. Paw volumes measured, radiography analysis, anti-oxidant status, Gene expression studies, western blot analysis and histological analysis were performed to check the effects of POH. RESULTS: Our in-vitro findings suggested that POH inhibits inflammation by suppressing reactive oxygen species (ROS), NF-кB and Nrf2 signaling axis. Besides this, POH also rescinded the nitrate levels, pro-inflammatory cytokine levels like IL-1ß, IL-6 and TNF-α also PGE2 and COX-2 levels induced by LPS in murine macrophages. Additionally, our in-vivo results revealed that POH conscientiously alleviated CFA induced inflammation by restoring arthritis index, body weight, nitrosative, lipid peroxidation assays. Macroscopically through measuring paw volumes and X-ray, it was evidenced that POH has decreased inflammation and bone erosion. Not only in-vitro but also in-vivo, POH has abridged cytokine levels IL-1ß, IL-6, and TNF-α. Histopathological evaluation presented POH treatment alleviated joint inflammation, pannus formation, and bone erosion significantly. Moreover, POH suppressed the protein expression of NF-кB, COX-2, iNOS and improved Nrf2, and SOD2 levels in paw tissues estimated by western blotting. CONCLUSION: POH was effective in ameliorating LPS stimulation mediated oxidative stress and pro-inflammatory cytokines in RAW 264.7 cells in-vitro and FCA induced arthritis in rats in-vivo through its anti-inflammatory effects via regulating TLR4/NF-κB and Keap1/Nrf2 signaling pathways..

Perillyl alcohol inhibits keratinocyte proliferation and attenuates imiquimod-induced psoriasis like skin-inflammation by modulating NF-κB and STAT3 signaling pathways.

Psoriasis is a chronic inflammatory and proliferative skin disease characterized by pathological skin lesions which significantly impact the quality of life. Recent studies have been proven that inhibitors of farnesyltransferase enzyme showed significant anti-psoriatic activity. Perillyl alcohol (POH) is one such natural molecule having anti proliferative, anti-inflammatory and anti-oxidant properties by inhibiting farnesyltransferase enzyme which further down regulates NF-κB and STAT3 via Ras/Raf/MAPK pathway. Hence, in the current study we aimed to find the effect of POH on human keratinocytes (HaCat) cells in in-vitro and IMQ induced psoriatic like skin inflammation model in mice. POH significantly decreased the intracellular ROS levels and inhibited the phosphorylation of NF-κB and STAT3 in in-vitro. It was found that POH (200 mg/kg, topical application) has reduced the epidermal hyperplasia, psoriasis area and severity index (PASI) scoring; splenomegaly in imiquimod (IMQ) induced psoriatic mice. Further, POH treatment has decreased the pro-inflammatory serum cytokine levels such as IL-6, IL-12/23, TNF-α and IL-1ß and also reduced the expression levels of various inflammatory proteins, COX-2, iNOS, IL-17A, IL-22, NF-кB and STAT3 evidenced by Immunoblotting studies from skin samples. The levels of endogenous antioxidants like glutathione GSH, SOD, Nrf2 were restored to normal levels upon POH treatment. POH downregulated the proteins levels of TLR7, TLR8, CyclinD1 and mRNA expression of Bcl-2 in the skin samples when compared to the IMQ group. POH has ameliorated the hyper-keratosis and acanthosis which was evidenced by histopathology. Collectively, our results suggest that POH has a promising therapeutic application for ameliorating psoriasis-like skin inflammation.