Inhibition of TNF-α, and NF-κB and JNK pathways accounts for the prophylactic action of the natural phenolic, allylpyrocatechol against indomethacin gastropathy.

BACKGROUND: The gastro-intestinal disorders, induced by the NSAIDs including indomethacin (IND) remain unresolved medical problems. Herein, we disclose allylpyrocatechol (APC) as a potential agent against IND-gastropathy and rationalize its action mechanistically. METHODS: Mice were pre-treated with APC for 1h followed by IND (18mgkg(-1)) administration, and the ulcer-prevention capacity of APC was evaluated on the 3rd day by histology. Its effect on the inflammatory (MPO, cytokines, adhesion molecules), ulcer-healing (COX, prostaglandins, growth factors and their receptors) and signaling parameters (NF-κB and MAPKs) were assessed by immunoblots/mRNA, and ELISA at the time points of their maximal changes due to IND administration. RESULTS: IND induced oxidative stress, triggering mucosal TNF-α that activated NF-κB and JNK MAPK signaling in mice. These increased the pro-inflammatory biochemical parameters, but reduced the healing factors. APC reversed all the adverse effects to prevent gastric ulceration. APC (5mgkg(-1)), trolox (50mgkg(-1)) and NAC (250mgkg(-1)) showed similar protection that was better than that by misoprostol (5µgkg(-1)) and omeprazole (3mgkg(-1)). CONCLUSIONS: The anti-ulcer effect of APC can be primarily attributed to its antioxidant action that helped in controlling various inflammatory parameters and augmenting angiogenesis. GENERAL SIGNIFICANCE: Given that APC is an effective, non-toxic antioxidant with appreciable natural abundance, further evaluation of its pharmacokinetics and dynamics would help in promoting it as a new anti-inflammatory agent.

Molecular mechanism of indomethacin-induced gastropathy.

The probable cross talk among large numbers of inflammatory and angiogenic parameters in indomethacin (IND)-induced gastropathy and the associated signaling mechanism were studied in a mouse model. A single dose of IND (18 mg/kg, po) produced robust gastric ulceration in mice without any mortality, which peaked on the third day, but started healing from the fifth day onward. The ulceration was associated with increased myeloperoxidase activity and expression of proinflammatory (TNF-α, adhesion molecules, COX-2) and antiangiogenic (endostatin) parameters. The levels of proangiogenic factors such as COX-1, prostaglandin E, VEGF, and von Willebrand factor VIII were downregulated by IND. Our results revealed that although the maximal and minimal levels of these parameters were attained sequentially at different time points, TNF-α upregulation was the primary event to initiate and induce gastric ulceration. IND also activated NF-κB and all the MAP kinases, but only the inhibitors of TNF-α, NF-κB, and JNK MAP kinase could abrogate the IND-induced damages. Further TNF-α inhibition also reduced the IND-mediated activation of NF-κB and JNK MAP kinase. All this evidence strongly suggests that mitigation of TNF-α may offer a potential solution to IND-mediated gastropathy.

Role of the COX-independent pathways in the ulcer-healing action of epigallocatechin gallate.

The modulation of the cyclooxygenase-independent pathway by the green tea-derived polyphenol, epigallocatechin gallate (EGCG) during its healing action against indomethacin (IND)-induced stomach ulceration in mice was investigated. On the 3rd day of its administration, IND (18 mg kg(-1)) induced maximum stomach ulceration which was associated with increased myeloperoxidase (MPO) activity (2.1-fold, p < 0.001), and inducible nitric oxide synthase (iNOS) expression (2.5-fold, p < 0.001), along with augmented levels of serum nitrite (1.3-fold, p < 0.001), selectins and cell adhesion molecules (CAMs), as well as reduced endothelial nitric oxide synthase (eNOS) expression (53%, p < 0.001). Treatment with EGCG (2 mg kg(-1)) and omeprazole (3 mg kg(-1)) for 3 days reversed these parameters, and provided excellent (76-77%) ulcer healing.

Epigallocatechin gallate accelerates healing of indomethacin-induced stomach ulcers in mice.

Management of the gastric toxicity of non-steroidal anti-inflammatory drugs (NSAIDs) remains a crucial problem because the commercially available drugs have side effects and are often expensive. Therefore, we examined the potential of the green tea-derived polyphenol epigallocatechin gallate (EGCG) to treat indomethacin-induced stomach ulcers in mice. Administration of indomethacin (18 mg/kg, po) to mice induced ulceration in the glandular portion of the gastric mucosa, accompanied by increased lipid peroxidation (LPO) and protein oxidation and reductions in thiol defense, mucin, cyclooxygenase (COX) expression and prostaglandin (PG) synthesis in the gastric tissues. Daily oral administration of EGCG (2 mg/kg) or omeprazole (3 mg/kg) for 3 days produced similar (≈ 72-75%, p < 0.001) beneficial effects on the acute gastric ulceration. Treatment with the test samples partially reversed all the adverse oxidative effects of indomethacin. In addition, EGCG, but not omeprazole, enhanced expression of the COX isoforms and PG synthesis. The results suggest that the non-toxic and inexpensive tea polyphenol EGCG may be an excellent candidate for further evaluation as a potent anti-ulcer drug.

Black tea and theaflavins suppress various inflammatory modulators and i-NOS mediated nitric oxide synthesis during gastric ulcer healing.

The modulation of the cyclooxygenase-independent pathway by black tea (BT) and its constituent theaflavins (TFs) during their healing action against indomethacin-induced stomach ulceration in mice was investigated. On the 3(rd) day of its administration, indomethacin (18 mg/kg) induced maximum stomach ulceration, which was associated with increased myeloperoxidase (MPO) activity (93.3%, p<0.001), and inducible nitric oxide synthase (iNOS) expression (1.6-fold, p<0.001), along with augmented levels of serum nitrite (1.5-fold, p<0.001), selectins and cell adhesion molecules (CAMs), as well as reduced endothelial nitric oxide synthase (eNOS) expression (60%, p<0.001). Treatment with BT (40 mg/kg) and TF (1 mg/kg) for 3 days reversed these parameters and provided excellent (78-81%) ulcer healing. However, alterations of NOS expressions and levels of selectins and CAMs were only partially responsible for the excellent healing capacity (∼80%) of omeprazole (3 mg/kg × 3 days).

Black tea and theaflavins assist healing of indomethacin-induced gastric ulceration in mice by antioxidative action.

The healing activities of black tea (BT) and the theaflavins (TF) against the indomethacin-induced stomach ulceration were studied in a mouse model. Indomethacin (18 mg/kg, p.o.) administration induced maximum ulceration in the glandular portion of the gastric mucosa on the 3rd day, accompanied by increased lipid peroxidation and protein oxidation, depletion of thiol-defense and mucin, as well as reduced expressions of cyclooxygenases (COX) and prostaglandin (PG) E synthesis in the gastric tissues, and plasma total antioxidant status of mice. Treatment with BT (40 mg/kg), TF (1 mg/kg), and omeprazole (3 mg/kg) produced similar (74%-76%) ulcer healing, as revealed from the histopathological studies. Treatment with all the above samples reversed the adverse oxidative effects of indomethacin significantly. BT and TF also enhanced the PGE synthesis by augmenting the expressions of COX 1 and 2, but did not modulate acid secretion.

The gastric ulcer-healing action of allylpyrocatechol is mediated by modulation of arginase metabolism and shift of cytokine balance.

The role of the ariginine-metabolism in the healing action of the Piper betle phenol, allylpyrocatechol (APC) and omeprazole against indomethacin-induced stomach ulceration in mouse was investigated. Indomethacin (18 mg/kg) was found to induce maximum stomach ulceration in Swiss albino mice on the 3rd day of its administration, which was associated with reduced arginase activity (21.6%, P<0.05), endothelial nitric oxide synthase (eNOS) expression (72%, P<0.001), and IL-4 and TGF-beta levels, along with increased inducible nitric oxide synthase (iNOS) (9.3 folds, P<0.001) expression, nitrite (2.29 folds, P<0.001), IL-1beta and IL-6 generation. Besides providing comparable healing as omeprazole (3 mg/kg x 3 days), APC (5 mg/kg x 3 days) shifted the iNOS/NO axis to the arginase/polyamine axis as revealed from the increased arginase activity (73.1%, P<0.001), eNOS expression (67.8%, P<0.001), and reduced iNOS expression (65.6%, P<0.001) and nitrite level (53.2%, P<0.001). These can be attributed to a favourable anti-/pro-inflammatory cytokines ratio, generated by APC. The healing by omeprazole was however, not significantly associated with those parameters.