Canonical Pathway of NF-κB which represents the pro-inflammatory response, and Keap-Nrf2-ARE Pathway which represents anti-inflammatory response. Both pathways may potentially affected by OPP for attenuating neuroinflammation. ⊕: activate or stimulate; ⊗: inhibit; ARE: antioxidant response element; CD40L: CD 40 ligand; COX-2: cyclooxygenase-2; E-Box: Enhancer Box; iNOS: inducible nitric oxide synthase; IL-1: Interleukin-1; I κKα, β, ɣ: IκB Kinase α, β, ɣ; KEAP1: Kelch-like ECH-associated protein 1; LPS: Lipopolysaccharide; Maf: Maf proteins; NF- κB: Nuclear Factor kappa-light-chain-enhancer of activated B cells; Nrf2: nuclear factor erythroid 2-related factor 2; RNS: reactive nitrogen species; ROS: reactive oxygen species; TNF-α: Tumour Necrosis Factor Alpha. This figure is modified from Shih et al. [101] and Weinberg et al. [56].