Celecoxib prevents colitis associated colon carcinogenesis: an upregulation of apoptosis.

BACKGROUND: Uncontrolled cell proliferation and suppressed apoptosis are the critical events transforming a normal cell to a cancerous one wherein the inflammatory microenvironment supports this oncogenic transformation. The process of colon carcinogenesis may be aggravated in chronic inflammatory conditions such as ulcerative colitis where non-steroidal anti-inflammatory drugs (NSAIDs) may effectively prevent the cellular and molecular events. METHODS: Western blots and immunofluorescent analysis of DNA mismatch repair enzymes, cell cycle regulators and pro- and anti-apoptotic proteins were performed in dextran sulfate sodium (DSS)-induced ulcerative colitis and 1,2-dimethyl benz(a)anthracene (DMH)-induced colon cancer. Also, apoptotic studies were done in isolated colonocytes using fluorescent staining and in paraffin sections using TUNEL assay. RESULTS: An upregulation of cell cycle regulators: cyclin D1/cdk4 and cyclin E/cdk2 and anti-apoptotic Bcl-2, along with the suppression of DNA repair enzymes: MLH1 and MSH2; tumour suppressors: p53, p21and Rb and pro-apoptotic proteins: Bax and Bad were observed in the DSS, DMH and DSS+DMH groups. Proliferating cell nuclear antigen (PCNA) was also overexpressed in these groups. The ultimate executioner of the apoptotic pathway; caspase-3, was suppressed in these groups. Apoptotic studies in colonocytes and paraffin sections revealed suppressed apoptosis in these groups. These effects were corrected with the administration of a second generation NSAID, celecoxib along with the treatment of DSS and DMH. CONCLUSION: The chemopreventive action of celecoxib in colitis mediated colon carcinogenesis may include the regulation of DNA mismatch repair enzymes, cell cycle check points, cell proliferation and apoptosis.

Up-regulation of p53 and mitochondrial signaling pathway in apoptosis by a combination of COX-2 inhibitor, Celecoxib and Dolastatin 15, a marine mollusk linear peptide in experimental colon carcinogenesis.

Programmed cell death, also known as apoptosis, is an active process occurring in eukaryotic cells and it depends on various sets of pro and anti-apoptotic proteins. Chemoprevention of colorectal cancer can be achieved by inducing apoptosis using synthetic compound, Celecoxib and natural peptide, Dolastatin 15 in an effective manner. But the apoptotic signaling by these two drugs remain unclear. The present study was thus focused on the role of Bcl2 family of proteins and their interplay with p53 in rats during the chemoprevention by these two drugs. After treatment for 6 wk with 1, 2-dimethylhydrazine (DMH), animals showed a marked occurrence of multiple plaque lesions. However, a simultaneous treatment with Celecoxib and Dolastatin 15 decreases such number to a significant level. DMH treatment also decreases the number of apoptotic cells in the colonic enterocytes which were corrected to the normal level by Celecoxib and Dolastatin 15. An increased expression of Bcl2 while other proteins like Bax, Apaf-1, cyt c, and caspases in the apoptotic pathway, and the tumor suppressor proteins, p53 and p21 get down-regulated after DMH treatment which were reverted back to normal with Celecoxib and Dolastatin 15. Also, cells having high mitochondrial membrane potential had been seen to increase to significant levels which were reduced after the administration of these anti-inflammatory drugs. In silico molecular docking studies also showed that Dolastatin 15 and Celecoxib may bind to the active site pocket of Bcl2 , thus revealing the direct target of Dolastatin 15 and Celecoxib apart from binding to COX-2.

Upregulation of intrinsic apoptotic pathway in NSAIDs mediated chemoprevention of experimental lung carcinogenesis.

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) act by inhibition of cyclooxygenase-2 (COX-2), which is overexpressed in cancer. The role of COX-2 and apoptosis were evaluated in 9,10-dimethylbenz(a)anthracene (DMBA)-induced lung cancer in rat and chemoprevention with indomethacin, a traditional NSAID and etoricoxib, a selective COX-2 inhibitor. METHODS: The animals were divided into Control, DMBA, DMBA+ indomethacin and DMBA+ etoricoxib groups. They received a single intratracheal instillation of DMBA while NSAIDs were given orally daily for 32 weeks. Besides morphology and histology of lungs, RT-PCR, western blots and immunohistochemistry were performed for the expression of apoptotic proteins and COX enzymes. Apoptosis was studied by DNA fragmentation and fluorescent staining. RESULTS: The occurrence of tumors and lesions was noted in the DMBA animals, besides constricted alveolar spaces and hyperplasia. COX-1 was found to be uniformly expressed while COX-2 level was raised significantly in DMBA group. The apoptotic proteins, apaf-1, caspase-9 and caspase-3 were highly diminished in DMBA group but restored to normal level in NSAIDs groups. Also, apoptosis was suppressed in carcinogen group by DNA fragmentation analysis and fluorescent staining of the lung cells while co-administration of NSAIDs along with DMBA led to the restoration of apoptosis. CONCLUSION: DMBA administration to the rats led to tumorigenesis in the lungs, had no effects on COX-1 expression, while elevating the COX-2 levels and suppressing apoptosis. The treatment with NSAIDs led to the amelioration of these effects. However, etoricoxib which is a COX-2 specific inhibitor, was found to be more effective than the traditional NSAID, indomethacin.

Chemopreventive effects of NSAIDs on cytokines and transcription factors during the early stages of colorectal cancer.

The earliest stages of colorectal cancer have been linked to inflammatory responses caused by carcinogens, but the molecular signaling of various pro- and anti-inflammatory cytokines and transcription factors in colorectal cancer remains unknown. The higher expression and secretion of various pro-inflammatory cytokines and their autocrine and paracrine functions play an important role in the activation of transcription factors, which in turn promote tumorigenesis. NF-κB serves as a vital biomolecule that transcribes a number of pro-inflammatory cytokines and anti-apoptotic proteins. Pro-inflammatory cytokines can also activate Jak3/Stat3 signaling pathways, thereby increasing inflammation and cell survival. In the present study, the expression of IL-1ß, IL-2, IL-4, IFNγ, TNF-α, iNOS, COX-2, Jak3, Stat3 and NF-κB were increased in the early stages of experimental colorectal cancer. The increased expression of these inflammatory molecules was reversed by the simultaneous administration of non-steroidal anti-inflammatory drugs (NSAIDs; sulindac and celecoxib). The anti-inflammatory activity of the NSAIDs was found to be mediated by the inhibition of NF-κB (p65) DNA-binding activity. The anti-neoplastic end effect of the NSAIDs in the isolated colonocytes was demonstrated by an increased level of apoptosis. This study suggests that NSAIDs inhibit NF-κB and Jak3/Stat3 signaling and down-regulate pro-inflammatory cytokines to a level that inhibits inflammation and carcinogenesis.

Antioxidative effects of nonsteroidal anti-inflammatory drugs during the initiation stages of experimental colon carcinogenesis in rats.

The role of nonsteroidal anti-inflammatory drugs (NSAIDs) was studied on the antioxidant defense system and nitric oxide-derived damage in a 1,2-dimethylhydrazine (DMH)-induced rat colon carcinogenesis. Early precancerous lesions were established in the proximal and distal regions of the colon by morphological and histopathological examinations that were greatly regressed by the simultaneous treatment of the three NSAIDs, such as aspirin, celecoxib, and etoricoxib, along with the procarcinogen DMH. The intestinal brush border membrane (BBM) was isolated from the two regions and the colon-specific marker enzyme cysteine-sensitive alkaline phosphatase was assayed, which showed considerable elevation by DMH but reverted back to normal level by all the three NSAIDs. DMH also caused a higher level of lipid peroxidation as measured by malonyldialdehyde production, which was also found to be corrected by the NSAIDs, in both the region of the colonic tissue. The antioxidant activities were further established by a higher level of superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase in the NSAID treatment as compared to the DMH. The nonenzyme tripeptide, glutathione content was also recovered similarly as an antioxidant defense mechanism. To elucidate whether nitric oxide (NO) also plays an important role in the pathophysiology of colon cancer, the NO and citrulline levels were measured. The results show that the NO was lowered in DMH treatment and elevated by the administration of the NSAIDs while the citrulline level could not be recovered back. The findings of the present investigation indicate the chemopreventive modalities of the NSAIDs, particularly the COX-2 inhibitors.

Chemopreventive effects of nonsteroidal anti-inflammatory drugs in the membrane lipid composition and fluidity parameters of the 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, celecoxib, and etoricoxib are reported to act as chemopreventive agents in experimental colon cancer induced by 1,2-dimethylhydrazine (DMH) as they are known cyclooxygenase (COX) enzyme inhibitors. To determine whether NSAIDs can also effectively modulate the membrane lipid compositions and the fluidity parameters of colonic brush border membrane, rats were injected subcutaneously (s.c.) with DMH 30 mg/kg body weight per week for 6 weeks. The animals were simultaneously treated with NSAIDs orally at the dose of aspirin, 60 mg/kg body weight; celecoxib, 6 mg/kg body weight; and etoricoxib, 0.6 mg/kg body weight. The animals were sacrificed after 6 weeks of treatments. Brush border membrane was isolated from proximal and distal portions of the colon. Membrane lipids were extracted and analyzed while the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. Colonic mucosal changes in DMH alone and DMH+NSAID treated animals were assessed histologically. The results demonstrate that (a) there is a distinct occurrence of premalignant alterations in DMH-induced colon in the form of multiple plaque lesions (MPLs), which were greatly reduced by the NSAIDs used, (b) the membrane lipid changes in DMH-induced colon were completely restored back, (c) the alterations in membrane fluorescence polarization and the fluidity parameters are partially recovered, particularly with etoricoxib, and (d) the pyrene excimer formation process was completely restored. It may be concluded that the NSAIDs, particularly the coxib group of the drugs (COX-2 selective), are effective in chemoprevention in the DMH-induced colon carcinogenesis and membrane alterations.

Effect of monensin, a Na+-specific carboxylic ionophore on the oxidative defense system in rat testis.

The effect of monensin, a Na+-specific ionophore on the oxidative defense system in rat testis was studied. Monensin mixed in the animal diet was administered at the dose levels of 2.5, 5 and 10 mg/kg b.w. to Wistar rats for a period of 67 days. A marked inhibition in the activities of different oxidative defense enzymes such as catalase, glutathione peroxidase, glutathione-S-transferase, superoxide dismutase and glutathione reductase was noticed, which indicates the possible involvement of free radicals in the antispermatogenic effects of monensin in rat testis. This was further substantiated by a significant increase in the generation of lipid peroxides along with the depletion of reduced glutathione. The drug treatment resulted in a significant change in apoptotic cell death as seen by an elevated fragmentation in the testicular genomic DNA. Monensin treatment also resulted in marked degenerative changes in the histoarchitecture of testis, such as depletion of different germ cell populations, vacuole formation and disorganization of seminiferous tubules. The results are indicative of the potential antispermatogenic effects of monensin in the rat.

Thermotropic lipid phase transition and the behavior of hydrolytic enzymes in the kidney cortex brush border membrane.

Functional interactions of lipids and proteins were examined in brush-border membranes isolated from the kidney cortex by studying the temperature dependence of the hydrolytic enzyme activities. A close relationship was observed for the membrane proteins and the thermotropic lipid phase transitions. Three lines of evidences were provided for such dependence: a) Arrhenius relationship of the membrane-bound enzyme activities, and the effect of temperature in native and partially delipidated membranes, b) differential scanning calorimetric study of the membrane lipid phase transitions in the native and delipidated membranes, multilamellar vesicles prepared from the membrane extracted lipids, and in vesicles from dimyristoyl phosphatidylcholine, and c) the excimer (dimer)-formation studies of the membrane extrinsic fluorescent probe, pyrene, and the resultant membrane microviscosity. The brush-border membranes were partially delipidated with BuOH and 2,2,2-trifluoroethanol. The functional interactions of the delipidated membranes, which were greatly lost on lipid removal, were largely restored by the addition of exogenous lipids in the reconstitution process, which indicate the critical dependence of the membrane integral proteins on the neighboring lipid molecules in the bulk lipid phase.

Use of phospholipid transfer protein as a probe to study the lipid dynamics and alkaline phosphatase activity in the brush border membrane of human term placenta.

Incubation of placental brush border membrane (BBM) along with sonicated vesicles of exogenous lipids (egg yolk PC) in the presence of phospholipid-transfer protein (PL-TP) showed a decrease in the alkaline phosphatase activity due to the change in the membrane micro-environment, such as fluidity. Effect of substrate concentration was tested by Lineweaver-Burk plot, which showed decreased V(max) and K(M). The effect of temperature was probed by the Arrhenius plot, which showed no change in transition temperature, but a decline in the energy of activation both below and above the transition temperature. The protein-catalyzed transfer of phospholipid from the donor unilamellar vesicles resulted in a substantial increase in the BBM phospholipid and a net decrease in cholesterol/phospholipid molar ratio. The change in membrane fluidity was assessed by translational as well as rotational diffusion of membrane extrinsic fluorescent probes, pyrene and diphenyl-hexatriene. An increased lateral mobility was recorded by the increased pyrene excimer formation. A decrease in fluorescent polarization of diphenyl-hexatriene was observed, which led to the decrease in fluorescence anisotropy and order parameter, and therefore, an increase in membrane fluidity (rotational diffusion). Mean anisotropy parameter was also decreased in the presence of PL-TP. Thus, the placental BBM alkaline phosphatase activity showed a distinct lipid dependence which may have important physiological consequences.

Effect of two non-steroidal anti-inflammatory drugs, aspirin and nimesulide on the D-glucose transport and disaccharide hydrolases in the intestinal brush border membrane.

The present study was designed to evaluate the effect of two commonly prescribed non-steroidal anti-inflammatory drugs (NSAIDs) with varying cyclooxygenase-2 (Cox-2) selectivities on enzyme activities and transport properties of rat intestinal brush border membrane (BBM). Female Wistar rats were divided into three different groups, viz: Group I (Control), Group II (aspirin-treated, 50 mg/kg) and Group III (nimesulide-treated, 10 mg/kg). At the end of 28 days of treatment, membranes were isolated from different intestinal segments of all the groups and changes in BBM-associated enzymes such as sucrase, lactase, maltase, alkaline phosphatase and the transport properties of D-glucose and its kinetics were studied. The results indicated a significant decrease in the activities of enzymes and transport of glucose in both the treatment groups as compared to the controls. Changes in Michaelis-Menten parameters, viz:--Km and Vmax and the thermodynamic parameters T(c) and E(a) were also seen which are indicative of adverse effects of these two NSAIDs in the intestinal membrane such as the membrane integrity.