Phosphodiesterase in human colon carcinoma cell line CaCo-2 in culture

Caffeine and its main targets of colorectal cancer

Caffeine is a purine alkaloid and is widely consumed in coffee, soda, tea, chocolate and energy drinks. To date, a growing number of studies have indicated that caffeine is associated with many diseases including colorectal cancer. Caffeine exerts its biological activity through binding to adenosine receptors, inhibiting phosphodiesterases, sensitizing calcium channels, antagonizing gamma-aminobutyric acid receptors and stimulating adrenal hormones. Some studies have indicated that caffeine can interact with signaling pathways such as transforming growth factor β, phosphoinositide-3-kinase/AKT/mammalian target of rapamycin and mitogen-activated protein kinase pathways through which caffeine can play an important role in colorectal cancer pathogenesis, metastasis and prognosis. Moreover, caffeine can act as a general antioxidant that protects cells from oxidative stress and also as a regulatory factor of the cell cycle that modulates the DNA repair system. Additionally, as for intestinal homeostasis, through the interaction with receptors and cytokines, caffeine can modulate the immune system mediating its effects on T lymphocytes, B lymphocytes, natural killer cells and macrophages. Furthermore, caffeine can not only directly inhibit species in the gut microbiome, such as Escherichia coli and Candida albicans but also can indirectly exert inhibition by increasing the effects of other antimicrobial drugs. This review summarizes the association between colorectal cancer and caffeine that is being currently studied.

Bamifylline Similar to Theophylline and Caffeine is a Competitive Inhibitor of the Cyclic Nucleotide Phosphodiesterase V

Bamifylline was found to be a poor inhibitor of 3′,5′-cyclic GMP phosphodiesterase (PDE V) as other methylxanthines such as teophylline and caffeine. The IC50 was respectively 3.24, 2.91, 1.69 mM. Inhibition decreased at higher cGMP concentrations. Lineweaver-Burk plots were linear or nearly linear. Differences in the actions of these inhibitors presumably reflect differences in the molecular requirements for effective interaction at the catalytic site on phosphodiesterase.

Genotoxicity and mutagenicity of melanoidins isolated from a roasted glucose–glycine model in human lymphocyte cultures, intestinal Caco-2 cells and in the Salmonella typhimurium strains TA98 and TA102 applying the AMES test

Melanoidins are formed during household cooking procedures and are part of our daily diet, but data on their toxicological potential are still scarce. Therefore, the mutagenic, cytotoxic and genotoxic activity of the water soluble total fraction (sol A), the water soluble high molecular weight fraction (HMW; Molecular weight>12,400 Da) and the remaining water soluble low molecular weight fraction (LMW) isolated from a glucose-glycine model system roasted at 125 degrees C was comprehensively studied in human lymphocytes (genetic end point: sister chromatid exchange (SCE)), Caco-2 cells (SCE, cell viability, cell proliferation) and in the Salmonella typhimurium strains TA98 and TA102 (Ames test). Tests were performed in a dose- and time-dependent manner. The results indicate a significant increase in SCE formation in human lymphocytes after the exposure to 0.05% and 0.1% of the melanoidin fractions. In Caco-2 cells, only the exposure to LMW increased the SCE formation as a matter of concentration. Cell's proliferation and viability decreased significantly after exposure to melanoidins. In the AMES test, melanoidins did not show a mutagenic potential, neither using the TA98 nor the TA102 strain. These results show that melanoidins isolated from the glucose-glycine mixture exhibited modest but significant genotoxic effects in human lymphocytes and, in particular the LMW, in Caco-2 cells, but they induce neither in low nor in very high concentrations mutagenicity in bacteria strains.

Cyclic guanosine monophosphate phosphodiesterase activity in human gingival carcinoma

BACKGROUND

Cyclic guanosine monophosphate (cGMP) is an essential second messenger metabolized by phosphodiesterases (PDEs).

OBJECTIVES

We looked for a possible correlation of PDE activities in human oral squamous cell carcinoma (OSCC) with and without lymph node metastases.

MATERIALS AND METHODS

The analysis of phosphodiesterase activity and the cGMP assay were done by reverse-phase HPLC on samples of fresh or frozen gingival tissues. Analysis of cGMP was confirmed with the enzyme-linked immunoabsorption assay.

RESULTS AND CONCLUSIONS

cGMP PDE activity was 34.92 +/- 7.17 SD, 12.89 +/- 4.43 SD, and 35.88 +/- 8.76 SD (nmols/mg of protein), respectively, in controls, samples without lymph node involvement (N-), and specimens with lymph node metastases (N+). cGMP values were 1.97 +/- 0.63 SD, 3.30 +/- 1.47 SD, and 3.49 +/- 1.47 SD (nmols/mg of protein). Our data support the hypothesis of a role for cGMP and PDE in the progression of OSCC.

Differential expression and function of PACAP and VIP receptors in four human colonic adenocarcinoma cell lines

Human colonic adenocarcinoma cell lines have conserved several features of the native tissue. Among these is the expression of cell surface receptors for hormones and neurotransmitters that may be involved in the regulation of proliferation and differentiation processes in these cancer cells. Here, we confirm that high-affinity binding sites for the Vasoactive Intestinal Polypeptide (VIP) and for the VIP analogue Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP), were expressed in 4 human colonic adenocarcinoma cell lines, HT29, SW403, DLD-1 and Caco-2, that spontaneously displayed variable phenotypic properties in culture. We demonstrated that after long-term treatments, VIP and PACAP significantly reduced cell proliferation in the 4 cell lines and modulated intracellular cAMP and cGMP levels. Furthermore, conspicuous differences were observed from one cell type to another concerning expression of the receptor subsets or the effects of the neuropeptides on cell growth and on cyclic nucleotides production.