Pivotal role of AKR1B1 in pathogenesis of colitis associated colorectal carcinogenesis

Identifying the target linking inflammation and oxidative stress to aggravate the disease progression will help to prevent colitis associated carcinogenesis. Since AKR1B1 overexpression is observed in inflammatory diseases and various cancers, we have investigated the role of AKR1B1 in colitis-associated colon carcinogenesis with the aid of epalrestat and its potent analogue NARI-29 (investigational molecule) as pharmacological probes. A TNF-α inducible NF-κB reporter cell line (GloResponse™ NF-κB-RE-luc2P HEK293) and dextran sodium sulfate (DSS) and 1,2 dimethyl hydrazine (DMH))-induced mouse model was used to investigate our hypothesis in vitro and in vivo. Clinically, an increased expression of AKR1B1 was observed in patients with ulcerative colitis. Our in vitro and in vivo findings suggest that the AKR1B1 modulated inflammation and ROS generation for the progression of colitis to colon cancer. AKR1B1 overexpression was observed in DSS + DMH-treated mice colons. Moreover, we could observe histopathological changes like immune cell infiltration, aberrant crypt foci, and tumour formation in DC groups. Mechanistically, we have witnessed modulation of the IKK/IκB/NF-κB and Akt/FOXO-3a/DR axis, increased inflammatory cytokines, increased expression of proliferative markers, Ki-67 and PCNA, and accumulation of β-catenin in the colon epithelium. However, pharmacological inhibition of AKR1B1 using NARI-29 or EPS has reversed the clinical, histopathological, and molecular alterations induced by DSS + DMH, confirming the obvious role of AKR1B1 in the promotion of colitis-associated carcinogenesis. In conclusion, our findings suggest that AKR1B1 targeted therapy could be a promising strategy for preventing CA-CRC and NARI-29 could be developed as a potent AKR1B1 inhibitor.

The role of FAS, FAS-L, BAX, and BCL-2 gene polymorphisms in determining susceptibility to unexplained recurrent pregnancy loss

PURPOSE

Idiopathic recurrent pregnancy loss (RPL) is a multifactorial reproductive disorder where an impaired control of apoptosis is likely involved. Triggering the cell death mechanism occurs in a spatiotemporal manner and is strongly related to a healthy pregnancy. Single nucleotide polymorphisms (SNPs) at the regulatory regions of genes are known to influence the expression patterns of apoptosis-related molecules.

METHODS

A total of 296 unrelated female Brazilian patients were evaluated for clinical-demographic variables and genetic factors: 140 women who had experienced an unexplained RPL (with at least two consecutive abortions) and 156 healthy multiparous women. In all patients, six SNPs were evaluated in genes of apoptosis-related pathways: FAS (rs2234767, rs1800682), FAS-L (rs763110, rs5030772), BAX (rs4645878), and BCL-2 (rs2279115) by PCR followed by a restriction fragment length polymorphism (RFLP)-based analysis.

RESULTS

The BAX-248GA genotype is independently associated with idiopathic RPL [adjusted OR = 0.30, 95% CI 0.13-0.70, P = 0.005] susceptibility. In the same multivariate model, the variables ethnicity, smoking, and alcohol consumption were statistically associated with RPL susceptibility (P < 0.05). No association with RPL susceptibility was reported for the remaining SNPs.

CONCLUSION

Our study is the first to evaluate the role of the main SNPs from both the extrinsic and intrinsic apoptosis pathways in RPL susceptibility. The association of BAX-248G/A with RPL susceptibility suggests that maternal predisposition for RPL has an essential contribution from genes involved in the delicate balance of endometrium cell turnover (cell death/proliferation). Therefore, apoptotic genes may represent promising targets for future studies on healthy pregnancies and the spectrum of pregnancy disorders.

Paraquat induces extrinsic pathway of apoptosis in A549 cells by induction of DR5 and repression of anti-apoptotic proteins, DDX3 and GSK3 expression

Paraquat (PQ) is a bipyridyl derivative herbicide known to cause lung toxicity partly through induction of apoptosis. Here we demonstrated that PQ caused apoptosis in A549 cells. PQ increased cleavage of caspase-8 and Bid, indicating caspase-8 activation and truncated Bid, the two key mediators of extrinsic apoptosis. Additionally, PQ treatment caused an increase in DR5 (death receptor-5) and caspase-8 interaction, indicating formation of DISC (death-inducing signaling complex). These results indicate that PQ induces apoptosis through extrinsic pathway in A549 cells. Moreover, PQ drastically increased DR5 expression and membrane localization. Furthermore, PQ caused prominent concentration dependent reductions of DDX3 (the DEAD box protein-3) and GSK3 (glycogen synthase kinase-3) which can associate with DR5 and prevent DISC formation. Additionally, PQ decreased DR5-DDX3 interaction, suggesting a reduction of DDX3/GSK3 anti-apoptotic complex. Inhibition of GSK3, which is known to promote extrinsic apoptosis by its pharmacological inhibitor, BIO accentuated PQ-induced apoptosis. Moreover, GSK3 inhibition caused a further decrease in PQ-reduced DR5-DDX3 interaction. Taken together, these results suggest that PQ may induce extrinsic pathway of apoptosis in A549 cells through upregulation of DR5 and repression of anti-apoptotic proteins, DDX3/GSK3 leading to reduction of anti-apoptotic complex.

Activation of Fas death receptor pathway and Bid in hepatocytes is involved in saikosaponin D induction of hepatotoxicity

Drug-induced liver injury can lead to acute liver failure. Saikosaponin D (SSD) is a major component isolated from the medicinal herb Bupleurum falcatum, which has been linked to hepatotoxicity. We previously reported that SSD disrupted PDGF-βR pathway leading to mitochondrial apoptosis in human LO2 hepatocytes. The present study was aimed at further exploring the underlying mechanisms in vitro and in vivo. We initially determined the concentration range of SSD at up to 2μM for subsequent apoptosis examinations. SSD significantly upregulated Fas expression, promoted caspase-8 cleavage and activated the pro-apoptotic protein Bid in LO2 cells. Moreover, SSD reduced the abundance of cytochrome c in mitochondria and increased the cleaved-caspase-3 in LO2 cells, but did not apparently affect PI3K/AKT, ERK and STAT3 pathways that are involved in cell fate regulation. Experiments in vivo showed that one-week treatment with SSD at 300 mg/kg significantly elevated the liver/body weight ratio and caused histological injury in mouse liver. Furthermore, SSD treatment induced massive hepatocyte apoptosis, and significantly downregulated Bcl-2 but upregulated Bax in mouse liver. Taken together, these results revealed a specific mechanism of activation of extrinsic apoptosis pathway and Bid by SSD, which was involved in SSD-induced mitochondrial apoptosis in hepatocytes and potential hepatotoxicity.

Downstream modulation of extrinsic apoptotic pathway in streptozotocin-induced Alzheimer's dementia in rats: Erythropoietin versus curcumin

Erythropoietin and curcumin showed promising neuroprotective effects in various models of Alzheimer's dementia. This study was designed to compare the beneficial effects of erythropoietin and/or curcumin in intracerebro-ventricular (ICV) streptozotocin-induced Alzheimer's like disease in rats. Rats received ICV injection of either saline (control, n=8 rats), or streptozotocin. Three weeks following surgery, streptozotocin-injected rats were assigned into 4 groups (8 rats each); vehicle, curcumin (80mg/kg/day, orally), erythropoietin (500 IU/kg every other day, intraperitoneally) and combined (curcumin and erythropoietin)-treated groups. After 3 months of treatment, rats were subjected to neurobehavioral testing, and then killed for biochemical and histological assessment of hippocampus. Fas ligand protein and caspase-8 activity as mediators of extrinsic apoptotic pathway, oxidative stress markers (malondialdehyde and reduced glutathione) and β-amyloid (1-40 and 1-42) peptides were measured. The results showed that administration of erythropoietin suppressed extrinsic apoptosis better than curcumin, while curcumin was more effective in combating oxidative stress in ICV-streptozotocin injected rats. Both erythropoietin and curcumin treatments (individually or combined) equally reduced the hippocampal β-amyloid accumulation and improved cognitive impairment in Morris water maze and passive avoidance tasks. The combined treatment was the most effective in ameliorating apoptosis and oxidative stress rather than behavioral responses or β-amyloid burden. In conclusion, ICV-streptozotocin-induced Alzheimer's dementia activates hippocampal Fas ligand-mediated apoptosis, which could be reduced by erythropoietin and/or curcumin treatment. Curcumin supplementation alone could ameliorate cognitive deficits and reverse biochemical alterations in ICV-streptozotocin Alzheimer's rat model without the hazardous polycythemic effect of long-term erythropoietin injection.

Apoptosis induced by Fas signaling does not alter hepatic hepcidin expression

AIM: To determine the regulation of human hepcidin (HAMP) and mouse hepcidin (hepcidin-1 and hepcidin-2) gene expression in the liver by apoptosis using in vivo and in vitro experimental models.

METHODS: For the induction of the extrinsic apoptotic pathway, HepG2 cells were treated with various concentrations of CH11, an activating antibody for human Fas receptor, for 12 h. Male C57BL/6NCR and C57BL/6J strains of mice were injected intraperitoneally with sublethal doses of an activating antibody for mouse Fas receptor, Jo2. The mice were anesthetized and sacrificed 1 or 6 h after the injection. The level of apoptosis was quantified by caspase-3 activity assay. Liver injury was assessed by measuring the levels of ALT/AST enzymes in the serum. The acute phase reaction in the liver was examined by determining the expression levels of IL-6 and SAA3 genes by SYBR green quantitative real-time PCR (qPCR). The phosphorylation of transcription factors, Stat3, Smad4 and NF-κB was determined by western blotting. Hepcidin gene expression was determined by Taqman qPCR. The binding of transcription factors to hepcidin-1 promoter was studied using chromatin immunoprecipitation (ChIP) assays.

RESULTS: The treatment of HepG2 cells with CH11 induced apoptosis, as shown by the significant activation of caspase-3 (P < 0.001), but did not cause any significant changes in HAMP expression. Short-term (1 h) Jo2 treatment (0.2 μg/g b.w.) neither induced apoptosis and acute phase reaction nor altered mRNA expression of mouse hepcidin-1 in the livers of C57BL/6NCR mice. In contrast, 6 h after Jo2 injection, the livers of C57BL/6NCR mice exhibited a significant level of apoptosis (P < 0.001) and an increase in SAA3 (P < 0.023) and IL-6 (P < 0.005) expression in the liver. However, mRNA expression of hepcidin-1 in the liver was not significantly altered. Despite the Jo2-induced phosphorylation of Stat3, no occupancy of hepcidin-1 promoter by Stat3 was observed, as shown by ChIP assays. Compared to C57BL/6NCR mice, Jo2 treatment (0.2 μg/g b.w.) of C57BL/6J strain mice for 6 h induced a more prominent activation of apoptosis, liver injury and acute phase reaction. Similar to C57BL/6NCR mice, the level of liver hepcidin-1 mRNA expression in the livers of C57BL/6J mice injected with a sublethal dose of Jo2 (0.2 μg/g b.w.) remained unchanged. The injection of C57BL/6J mice with a higher dose of Jo2 (0.32 μg/g b.w.) did not also alter hepatic hepcidin expression.

CONCLUSION: Our findings suggest that human or mouse hepcidin gene expression is not regulated by apoptosis induced via Fas receptor activation in the liver.

Caspase-8 mutations in head and neck cancer confer resistance to death receptor-mediated apoptosis and enhance migration, invasion, and tumor growth

Little is known regarding molecular markers in head and neck squamous cell carcinoma (HNSCC) that predict responsiveness to different therapeutic regimens or predict HNSCC progression. Mutations in procaspase-8 occur in 9% of HNSCC primary tumors, but the functional consequences of these mutations are poorly understood. In this study, we examined the impact of four, representative, HNSCC-associated procaspase-8 mutations on activation of the extrinsic apoptosis pathway, as well as cellular migration and invasion, and in vivo tumor growth. All four mutant proteins acted to potently inhibit activation of apoptosis following treatment with TRAIL or agonistic anti-Fas. In contrast to wild-type procaspase-8, the mutant proteins were not recruited to FADD following treatment with TRAIL or anti-Fas, but may be constitutively bound by FADD. Three of the four procaspase-8 mutants promoted enhanced cellular migration and invasion through matrigel, relative to that seen with the wild-type procaspase-8 protein. Procaspase-8 mutation also stimulated the growth of HNSCC xenograft tumors. These findings indicate that HNSCC-associated procaspase-8 mutations inhibit activation of the extrinsic apoptosis pathway and are likely to represent markers for resistance to therapeutic regimens incorporating death receptor activators. Moreover, procaspase-8 mutations may serve as markers of HNSCC tumor progression, as exemplified by enhanced migration, invasion, and tumor growth.

Involvement of extrinsic and intrinsic apoptotic pathways together with endoplasmic reticulum stress in cell death induced by naphthylchalcones in a leukemic cell line: advantages of multi-target action

Chalcones, naturally occurring open-chain flavonoids abundant in plants, have demonstrated anticancer activity in multiple tumor cells. In a previous work, the potential anticancer activity of three naphthylchalcones named R7, R13 and R15 was shown. In this study, the mechanism of actions of these chalcones was originally shown. The chalcones presented concentration and time-dependent cytotoxicity. To determine the type of cell death induced by chalcones, we assessed a series of assays including measurements of the caspase-8, -9 and -12 activities, expression of important apoptosis-related genes and proteins, changes in the cell calcium concentration and cytochrome c release. The activities of caspase-8, -9 and -12 increased after the treatment of L1210 cells with the three compounds. Chalcones R7 and R13 induced an increase of pro-apoptotic proteins Bax, Bid and Bak (only chalcone R13), as well as a decrease in anti-apoptotic Bcl-2 expression. These chalcones also induced an increase in Fas and a decrease in p21 and p53 expression. Chalcone R15 seems to act by a different mechanism to promote cell death, as it did not change the mitochondrion-related proteins, nor did it induce the cytochrome c release. All compounds induced an increase in cell calcium concentration and an increase in CHOP expression, which together with an increase in caspase-12 activity, suggest that chalcones could induce an endoplasmic reticulum (ER) stress. Taken together, these results suggest that chalcones induce apoptosis by different pathways, being an interesting strategy to suggest for cancer therapy.