Drug Discovery of New Anti-Inflammatory Compounds by Targeting Cyclooxygenases

Abstract

The goal of achieving anti-inflammatory efficacy with the fewest possible adverse effects through selective COX-2 inhibition is still being investigated in order to develop drugs with safe profiles. This work shows the efficacy and safety profile of two novel benzimidazole piperidine and phenoxy pyridine derivatives in reaching this goal, which would be considered a major achievement in inflammatory therapy. The compounds were evaluated by virtual screening campaign, in vitro cyclooxygenase 1 and 2 (COX-1 and COX-2) inhibition, in vivo carrageenan-induced rat paw edema assay, cytotoxicity against Raw264.7 cells, and histopathological examination of rat paw and stomach. Two new compounds, compound 1 ([(2-{[3-(4-methyl-1H-benzimidazol-2-yl)piperidin-1-yl]carbonyl}phenyl)amino]acetic acid) and compound 2 (ethyl 1-(5-cyano-2-hydroxyphenyl)-4-oxo-5-phenoxy-1,4-dihydropyridine-3-carboxylate) showed high selectivity against COX-2, favourable drug-likeness and ADME descriptors, a lack of cytotoxicity, relived paw edema, and inflammation without noticeable side effects on the stomach. These two compounds are promising new NSAIDs.

Keywords: cyclooxygenase; docking; drug discovery; lipoxygenase; non-steroidal anti-inflammatory drugs.

Figure 1

Compounds’ chemical names, structures, and IDs. The compounds were purchased from Chembridge (San Diego, CA, USA).

Figure 2

The docking site and ligand interactions of compounds 1–7. The ligand interaction of every compound is provided. Positively charged residues are in blue, while hydrophobic residues are in green. Salt bridges are depicted as double-colored lines in blue and red. Stacking interactions are represented by green lines.

Figure 3

Average rats paw edema size (cm). The control group was treated with 0.2 mL of 1% carrageenan. Compounds 1, 2, and 3 were given orally at a dose rate of 10 mg/kg. The control nontreated group received NaCMC. The rat paw size was evaluated for 5 h after treatment. Each column represents the mean ± SD. Mean values in each plot followed by a different lowercase letter (a, b, c, d, e and f) are significantly different at p ≤ 0.05.

Figure 4

The progress of rat paw edema (cm) for 5 h after compounds administration. The control group was treated with 0.2 mL of 1% carrageenan. Compounds 1, 2, and 3 were given orally at a dose rate of 10 mg/kg. The control nontreated group received NaCMC. The measurement was performed at 0, 30 min, 1, 2, 3, 4 and 5 h after administration of the drugs.

Figure 5

Histopathologic examination of rat paw stained by H&E. (A) Photomicrograph of control rat paw at 10× magnification showing normal epidermal layers (E), dermis (D), and muscle layer (M); notice the absence of any signs of an inflammatory reaction. (B) Photomicrograph of control rat paw at 40× magnification showing normal SC, stratum corneum; SGr, stratum granulosum; SS, stratum spinosum; and SG, stratum germinativum. (C) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group showing marked thickening of the dermal layer, inflammatory reaction in the deep dermis, and wide separation between fibers due to edema (Od). (D) Photomicrograph of rat paw at 40× magnification of carrageenan-treated group showing edema (Od). (E) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with compound 1 showing a significant decrease in the dermal thickness, inflammatory reaction in the deep dermis (black star), and moderate improvements in edema (Od). (F) Photomicrograph of rat paw at 40× magnification of carrageenan-treated group followed by treatment with compound 1 showing slight inflammatory reaction (black star) and edema (Od). (G) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with compound 2 showing a substantial decrease in both the inflammatory reaction (black star) and edema (Od). (H) Photomicrograph of rat paw at 40× magnification of carrageenan-treated group followed by treatment with compound 2 showing slight inflammatory reaction (black star) and edema (Od). (I) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with compound 3 showing a significant decrease in the degree of inflammatory reaction (black star) and a moderate decrease in edema (Od). (J) Photomicrograph of rat paw at 40× magnification of carrageenan-treated group followed by treatment with compound 3 showing moderate inflammatory reaction (black star) and edema (Od). (K) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with indomethacin showing a significant decrease in the degree of inflammatory reaction (black star) and a moderate decrease in edema (Od). (L) Photomicrograph of rat paw at 40× magnification of carrageenan-treated group followed by treatment with indomethacin showing slight inflammatory reaction (black star) and edema (Od).

Figure 6

Histopathologic examination of rat paw stained by Masson’s Trichrome stain. Collagen fibrils are stained blue-green. The double-headed arrow represents collagen fibrils thickness between epidermis and dermis. (A) Photomicrograph of control rat paw at 10× magnification showing normal collagen deposition. (B) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group showing intense collagen deposition. (C) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with compound 1 showing slight collagen deposition (D). Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with compound 2 showing slight collagen deposition. (E) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with compound 3 showing significant collagen deposition. (F) Photomicrograph of rat paw at 10× magnification of carrageenan-treated group followed by treatment with indomethacin showing slight collagen deposition.

Figure 7

Histopathologic examination of rat stomach stained by H&E. (A) Photomicrograph of control rat stomach at 10× magnification showing normal gastric layers. Blue arrow shows intact appearance of histological structure of the epithelium and mucosa layer; GM, Gastric Mucosa; GS, Gastric Submucosa. (B) Photomicrograph of control rat stomach at 40× magnification showing absence of any signs of an inflammatory reaction. (C) Photomicrograph of rat stomach at 10× magnification of treatment with compound 1 showing normal gastric layers. Blue arrow shows intact appearance of histological structure of the epithelium and mucosa layer; GM, Gastric Mucosa; GS, Gastric Submucosa. (D) Photomicrograph of rat stomach at 40× magnification of treatment with compound 1 showing absence of any signs of an inflammatory reaction. (E) Photomicrograph of rat stomach at 10× magnification of treatment with compound 2 showing normal gastric layers. Blue arrow shows intact appearance of histological structure of the epithelium and mucosa layer; GM, Gastric Mucosa; GS, Gastric Submucosa. (F) Photomicrograph of rat paw at 40× magnification of treatment with compound 2 showing absence of any signs of an inflammatory reaction. (G) Photomicrograph of rat stomach at 10× magnification of treatment with compound 3 showing slight degeneration of gastric layers. (H) Photomicrograph of rat paw at 40× magnification of treatment with compound 3 showing absence of any signs of an inflammatory reaction. (I) Photomicrograph of rat stomach at 10× magnification of treatment with indomethacin, showing slight degeneration of gastric layers. (J) Photomicrograph of rat paw at 40× magnification of treatment with indomethacin showing absence of any signs of an inflammatory reaction.

Figure 8

Histopathologic examination of rat stomach stained by Masson’s Trichrome. Collagen fibrils are stained blue-green. The double-headed arrow represents collagen fibrils thickness in the submucosa. (A) Photomicrograph of control rat stomach at 10× magnification showing normal collagen deposition. (B) Photomicrograph of rat stomach at 40× magnification of control group showing normal collagen deposition. (C) Photomicrograph of rat stomach at 10× magnification of treatment with compound 1 showing normal collagen deposition. (D) Photomicrograph of rat stomach at 40× magnification of treatment with compound 1 showing normal collagen deposition. (E) Photomicrograph of rat stomach at 10× magnification of treatment with compound 2 showing slight collagen deposition. (F) Photomicrograph of rat stomach at 40× magnification of treatment with compound 2 showing slight collagen deposition. (G) Photomicrograph of rat stomach at 10× magnification of treatment with compound 3 showing significant collagen deposition. (H) Photomicrograph of rat stomach at 40× magnification of treatment with compound 3 showing significant collagen deposition. (I) Photomicrograph of rat stomach at 10× magnification of treatment with indomethacin showing significant collagen deposition. (J) Photomicrograph of rat stomach at 40× magnification of treatment with indomethacin showing collagen deposition.