Targeting Fatty Acid Binding Protein (FABP) Anandamide Transporters – A Novel Strategy for Development of Anti-Inflammatory and Anti-Nociceptive Drugs

Abstract

Fatty acid binding proteins (FABPs), in particular FABP5 and FABP7, have recently been identified by us as intracellular transporters for the endocannabinoid anandamide (AEA). Furthermore, animal studies by others have shown that elevated levels of endocannabinoids resulted in beneficial pharmacological effects on stress, pain and inflammation and also ameliorate the effects of drug withdrawal. Based on these observations, we hypothesized that FABP5 and FABP7 would provide excellent pharmacological targets. Thus, we performed a virtual screening of over one million compounds using DOCK and employed a novel footprint similarity scoring function to identify lead compounds with binding profiles similar to oleic acid, a natural FABP substrate. Forty-eight compounds were purchased based on their footprint similarity scores (FPS) and assayed for biological activity against purified human FABP5 employing a fluorescent displacement-binding assay. Four compounds were found to exhibit approximately 50% inhibition or greater at 10 µM, as good as or better inhibitors of FABP5 than BMS309403, a commercially available inhibitor. The most potent inhibitor, γ-truxillic acid 1-naphthyl ester (ChemDiv 8009-2334), was determined to have Ki value of 1.19±0.01 µM. Accordingly a novel α-truxillic acid 1-naphthyl mono-ester (SB-FI-26) was synthesized and assayed for its inhibitory activity against FABP5, wherein SB-FI-26 exhibited strong binding (Ki 0.93±0.08 µM). Additionally, we found SB-FI-26 to act as a potent anti-nociceptive agent with mild anti-inflammatory activity in mice, which strongly supports our hypothesis that the inhibition of FABPs and subsequent elevation of anandamide is a promising new approach to drug discovery. Truxillic acids and their derivatives were also shown by others to have anti-inflammatory and anti-nociceptive effects in mice and to be the active component of Chinese a herbal medicine (Incarvillea sinensis) used to treat rheumatism and pain in humans. Our results provide a likely mechanism by which these compounds exert their effects.

Fatty Acid-binding Proteins (FABPs) Are Intracellular Carriers for Δ9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD)

“…In agreement with previous studies, CBD inhibited both rat and mouse but not human FAAH (Fig. 3D), suggesting a species specificity that may underlie these effects (14,44). To further investigate this species specificity, we employed site-directed mutagenesis to interconvert key residues within the active site of human FAAH to the homologous residues found in rat FAAH.…”

“…HeLa cells are a suitable cell type to examine interactions of exogenous cannabinoids with FABPs and their effects upon endocannabinoid transport because these cells conveniently express a single FABP subtype, FABP5 (12,14), AEA uptake is coupled to its breakdown by FAAH (42,43). Therefore, HeLa cells, which lack FAAH (44), were transfected with human FAAH and AEA uptake was subsequently examined.…”

Fatty acid binding proteins

“…Interestingly, a biphasic expression of FABP5 was observed in this study, with an initial down-regulation as part of immune response initiation, followed by recovery of expression levels to aid attenuation of the inflammatory response, possibly in conjunction with increased expression of PPAR (39). A specific inhibitor of FABP5, namely AM404, was used to show that FABP5 enhances the action of Nacylethanolamine, a PPAR agonist, by increasing its uptake and nuclear translocation in Hela cells (38). Thus, several studies have shown that FABP5 interacts with the PPAR class of nuclear receptors and we speculate that these interactions are cell-and tissue-dependent, while probably also driven by substrate supply and the metabolic requirements of the specific cells.…”

“…FABP5 has been found at detectable levels in adipocytes, macrophages, endothelial cells, lung epithelium, neural tissues and breast tumour (1)(37) (38). The role of FABPs in regulating cell proliferation is also seen with FABP5, where levels are up-regulated in breast tumours, promoting proliferation and metastatis in cultured cells, most likely through interactions with PPAR (37).…”

Nuclear Factor Erythroid 2-Related Factor 2 Deficiency Results in Amplification of the Liver Fat-Lowering Effect of Estrogen

“…peroxisome proliferator-activated receptor, exhibiting properties of anti-inflammation and antioxidative stress (Berger et al, 2012;Gally et al, 2013). Overexpression of FABP5 in adipose tissue results in increased lipolysis, decreased fat mass, and potentiated insulin resistance (Hertzel et al, 2006).…”