Chemoselective Esterification of Natural and Prebiotic 1,2-Amino Alcohol Amphiphiles in Water.

In cells, a vast number of membrane lipids are formed by the enzymatic O-acylation of polar head groups with acylating agents such as fatty acyl-CoAs. Although such ester-containing lipids appear to be a requirement for life on earth, it is unclear if similar types of lipids could have spontaneously formed in the absence of enzymatic machinery at the origin of life. There are few examples of enzyme-free esterification of amphiphiles in water and none that can occur in water at physiological pH using biochemically relevant acylating agents. Here we report the unexpected chemoselective O-acylation of 1,2-amino alcohol amphiphiles in water directed by Cu(II) and several other transition metal ions. In buffers containing Cu(II) ions, mixing biological 1,2-amino alcohol amphiphiles such as sphingosylphosphorylcholine with biochemically relevant acylating agents, namely, acyl adenylates and acyl-CoAs, leads to the formation of the O-acylation product with high selectivity. The resulting O-acylated sphingolipids self-assemble into vesicles with markedly different biophysical properties than those formed from their N-acyl counterparts. We also demonstrate that Cu(II) can direct the O-acylation of alternative 1,2-amino alcohols, including prebiotically relevant 1,2-amino alcohol amphiphiles, suggesting that simple mechanisms for aqueous esterification may have been prevalent on earth before the evolution of enzymes.

Selective C-H Iodination of (Hetero)arenes.

Iodoarenes are versatile intermediates and common synthetic targets in organic synthesis. Here, we present a strategy for selective C-H iodination of (hetero)arenes with a broad functional group tolerance. We demonstrate the utility and differentiation to other iodination methods of supposed sulfonyl hypoiodites for a set of carboarenes and heteroarenes.

Synthesis of Benzylic Alcohols by C-H Oxidation.

Selective methylene C-H oxidation for the synthesis of alcohols with a broad scope and functional group tolerance is challenging due to the high proclivity for further oxidation of alcohols to ketones. Here, we report the selective synthesis of benzylic alcohols employing bis(methanesulfonyl) peroxide as an oxidant. We attempt to provide a rationale for the selectivity for monooxygenation, which is distinct from previous work; a proton-coupled electron transfer mechanism (PCET) may account for the difference in reactivity. We envision that our method will be useful for applications in the discovery of drugs and agrochemicals.

Late-Stage Aromatic C-H Oxygenation.

Synthetic methods for oxidative aromatic C-O bond formation are sparse, despite their demand in metabolite synthesis for drug discovery and development. We report a novel methodology for late-stage C-O bond formation of arenes. The reaction proceeds with excellent functional group tolerance even for highly functionalized substrates. The resulting aryl mesylates provide access to potential human metabolites of pharmaceuticals, and may be used directly to install a C-F bond to block metabolic hotspots. A charge-transfer interaction between the reagent bis(methanesulfonyl) peroxide and the substrate arenes may be relevant for the chemoselective functionalization of arenes over other functional groups.

Chemopreventive effects of non-steroidal anti-inflammatory drugs in early neoplasm of experimental colorectal cancer: an apoptosome study.

PURPOSE: Apoptosis is a highly regulated mechanism of cell death where pro-apoptotic proteins and caspases play an important role. Activation of pro-caspases at a definite time is essential to control the whole caspase cascade. Mitochondrion contains some pro-apoptotic proteins, which need to come out in cytoplasm for apoptotic function such as Cytochrome c (Cyt c), while the Bcl-2 protein family works as the guard of mitochondrial membrane and prevents the escape of Cyt c. Once Cyt c is out in cytoplasm, it binds with Apaf-1 (another pro-apoptotic protein also essential for proper cell differentiation) and pro-caspase-9, forming the Apoptosome complex. In this study, the role of two non-steroidal anti-inflammatory drugs (NSAIDs), Diclofenac and Celecoxib, in experimentally induced early neoplasm of colon via apoptosome mechanism had been studied. It has been recognized that the prolonged use of NSAIDs has its effect on reducing the risk of colorectal cancer through apoptotic pathways. However, the role of NSAIDs in respect of apoptosome is not clear. METHODS: Western blotting and immunohistochemistry were performed, along with morphological and histological analysis. RESULTS: According to the expression levels of Cytochrome c, Apaf-1, Caspases, and Bcl-2, it was observed that NSAIDs do follow the mitochondrial or intrinsic pathway of apoptosis. CONCLUSION: The effects of Diclofenac and Celecoxib on the expression of pro- and anti-apoptotic proteins have been observed, which may constitute the mechanism by which the NSAIDs are efficient in controlling the proliferation of neoplasm in the colon.

The role of NF-κB and PPARγ in experimentally induced colorectal cancer and chemoprevention by cyclooxygenase-2 inhibitors.

Initiation of malignancy is dependent upon the basic ratio of cell proliferation and apoptosis. Many molecular proteins and pathways are responsible for the imbalance of proliferation and apoptosis ratio. For example, Akt is a key biomolecule which regulates the cell survival signals via various downstream pathways. One of those pathways is nuclear factor-κB activation which also regulates many downstream pathways that are essential for cell survival. Along with these anti-apoptotic pathways, cells do have a parallel mechanism to prevent malignancy with the help of the ligand-induced nuclear receptors, e.g., peroxisome proliferator-activated receptor gamma (PPARγ). PPARγ has been found to be expressed in many cancer cell types and reported to be a pro-apoptotic transcription factor. The study aimed to observe the ability of two cyclooxygenase-dependent non-steroidal anti-inflammatory drugs (NSAIDs) in the prevention of experimentally induced early neoplasm of colon via NF-κB and PPARγ pathways. Early stages of colorectal cancer were produced in rats with 1,2-dimethylhydrazine dihydrochloride. Western blotting and immunohistochemistry were performed along with morphological and histological analysis. According to the expression levels of NF-κB and PPARγ in the cell nuclei, it is observed that NSAIDs may prevent colorectal cancer in the early stages by a concomitant down-regulation of NF-κB and up-regulation of PPARγ. COX-independent mechanism of anti-carcinogenesis was observed by COX-dependent NSAIDs in colorectal cancer.

Chemopreventive role of etoricoxib (MK-0663) in experimental colon cancer: induction of mitochondrial proapoptotic factors.

This study explored the role of intrinsic mitochondrial membrane potential (DeltaPsiM) in etoricoxib-mediated apoptosis in 1,2-dimethylhydrazine dihydrochloride (DMH) induced colon cancer. Male Sprague--Dawley rats were divided into four groups: control, DMH, DMH+etoricoxib and etoricoxib. After 6 weeks of treatment period, animals were killed and colons were analyzed for morphological and histopathological features. Well-characterized preneoplastic aberrations such as multiple plaque lesions, hyperplasia and dysplasia were found in the DMH-treated group whereas these features were reduced with coadministration of etoricoxib and DMH. DeltaPsiM was assessed by 5,5',6,6'-tetrachloro-1,1',3,3' tetraethylbenzimidazol carbocyanine iodide (JC-1) fluorescent staining of the isolated colonocytes. DMH treatment led to a significant increase in DeltaPsiM which was found to be low in the DMH+etoricoxib group. The expression of important proapoptotic proteins, cytochrome C and Bax, were analyzed by western blot and immunohistochemistry. DMH treatment reduced the expression of Bax and cytochrome C whereas etoricoxib promoted the expression of the same. Protein expression of antiapoptotic protein Bcl-2 was also studied in colonic mucosa and was found high in the DMH-treated group and low in DMH+etoricoxib treated animals. Etoricoxib treatment may exert its chemopreventive action in colon carcinogenesis by modulating the DeltaPsiM.

Anti-proliferative and apoptotic effects of etoricoxib, a selective COX-2 inhibitor, on 1,2-dimethylhydrazine dihydrochloride-induced colon carcinogenesis.

In the present study, we assessed effects of etoricoxib, a non-steroidal anti-inflammatory drug, on proliferation and apoptosis in 1,2-dimethylhydrazine dihydrochloride (DMH) induced colon lesion development. Male SD rats were divided into four groups: Group 1 controls receiving the vehicle treatment; Group 2 administered DMH weekly (30 mg/kg body weight, subcutaneously) alone; Group 3, DMH weekly plus etoricoxib (0.64 mg/kg body weight, orally) daily; and Group 4, etoricoxib alone. After six weeks of treatment, animals were sacrificed and colons were analysed for morphological and histopathological features. Well characterized pre-neoplastic aberrations such as multiple plaque lesions, hyperplasia and dysplasia were found in the DMH treated group whereas these features were reduced with co-administration of etoricoxib. To study apoptosis, colonocytes were isolated by metal chelation from colonic sacs and studied by fluorescent staining and further confirmed by DNA fragmentation. The DMH treated animals had fewer apoptotic nuclei as compared to the controls, but numbers were higher with DMH+etoricoxib as well as etoricoxib alone. Expression of proliferative cell nuclear antigen (PCNA), assessed by Western blot analysis and immunohistochemistry, was found to be elevated by DMH treatment group and again reduced by etoricoxib. Results for bromodeoxyuridine incorporation (BrdU) were in agreement. It may be concluded that the drug, etoricoxib, has the potential to act as an anti-apoptotic and anti- proliferative agent in the colon.

Celecoxib administration exhibits tissue specific effect on 3H-benzo(a)pyrene-DNA adduct formation in cigarette smoke inhaling mice.

In the present study, cigarette smoke (CS) exposure significantly enhanced 3H-B(a)P-DNA adduct formation in both the pulmonary and hepatic tissues. Mice co-treated with CS and celecoxib (a specific COX-2 inhibitor) exhibited a significant decrease in hepatic carcinogen-DNA adduct formation in comparison to the smoke exposed group, however the lungs of the co-treated animals exhibited a significant increase in carcinogen-DNA adduct formation when compared to the control group and smoke exposed group. CS exposure enhanced the activity of carcinogen activation enzymes in both the tissues and decreased the activity of carcinogen detoxification enzymes in the hepatic tissue only, when compared to the control group. Celecoxib administration to CS inhaling mice modulated the carcinogen biotransformation considerably when compared to the CS exposed group. Celecoxib administration to CS inhaling mice produced a low index of carcinogenesis in the hepatic tissue but increased the index of carcinogenesis in the pulmonary tissue. These observations seem to be critical and tissue specific when related to carcinogenesis.

Chemoprevention of 1,2-dimethylhydrazine-induced colon carcinogenesis by a non-steroidal anti-inflammatory drug, etoricoxib, in rats: inhibition of nuclear factor kappaB.

Etoricoxib, a highly selective cyclooxygenase- 2 (COX-2) inhibitor (a non steroidal anti-inflammatory drug) used for the treatment of rheumatoid arthritis and osteoarthritis, has been newly marketed and studied for the chemopreventive response in the 1,2-dimethylhydrazine dihydrochloride (DMH) induced rat colon cancer model. Male Sprague-Dawley rats were divided into four groups. Group I served as the Control and received the vehicle treatment, while Groups 2 and 3 were administered freshly prepared DMH (30 mg/kg body weight, subcutaneously) in 1mM EDTA-saline (pH 7.0). Groups 3 and 4 received Etoricoxib (0.64 mg/kg body weight, orally) daily prepared in 0.5% carboxymethyl cellulose. After a 6 week treatment period, animals were sacrificed and the colons were subjected to macroscopic and histopathological studies. Well characterized pre-neoplastic features such as multiple plaque lesions (MPLs), aberrant crypts (ACs) and aberrant crypt foci (ACF) were found in the DMH group. The number was reduced in DMH + Etoricoxib group, while very few MPLs and ACFs were recorded in the Etoricoxib only group. Also, histologically well characterized dysplasia and hyperplasia were observed in DMH treated group. The simultaneous administration of DMH and Etoricoxib reduced these features. To study apoptosis, colonocytes were isolated by metal chelation from colonic sacs and studied by fluorescent staining. The DMH treated animals produced much less apoptotic nuclei as compared to the Control. The number of apoptotic nuclei was also found higher in the DMH + Etoricoxib group as well as in Etoricoxib only group. Studies of a nuclear transcription factor (NF-kB) and COX-2 by Western blot analysis and immunohistochemistry demonstrated expression of both to be elevated in the DMH treated group but reduced in the DMH + Etoricoxib group. Expression was also low in the Etoricoxib only group. It may be concluded that the drug, Etoricoxib, has the potential to reduce DMH induced colon cancer development.