CYP11A1‑derived vitamin D hydroxyderivatives as candidates for therapy of basal and squamous cell carcinomas

Hydroxyderivatives of vitamin D3, including classical 1,25(OH)2D3 and novel CYP11A1‑derived hydroxyderivatives, exert their biological activity by acting as agonists on the vitamin D receptor (VDR) and inverse agonists on retinoid‑related orphan receptors (ROR)α and γ. The anticancer activities of CYP11A1‑derived hydroxyderivatives were tested using cell biology, tumor biology and molecular biology methods in human A431 and SCC13 squamous (SCC)‑ and murine ASZ001 basal (BCC)‑cell carcinomas, in comparison with classical 1,25(OH)2D3. Vitamin D3‑hydroxyderivatives with or without a C1α(OH) inhibited cell proliferation in a dose‑dependent manner. While all the compounds tested had similar effects on spheroid formation by A431 and SCC13 cells, those with a C1α(OH) group were more potent in inhibiting colony and spheroid formation in the BCC line. Potent anti‑tumorigenic activity against the BCC line was exerted by 1,25(OH)2D3, 1,20(OH)2D3, 1,20,23(OH)3D3, 1,20,24(OH)3D3, 1,20,25(OH)3D3 and 1,20,26(OH)3D3, with smaller effects seen for 25(OH)D3, 20(OH)D3 and 20,23(OH)2D3. 1,25(OH)2D3, 1,20(OH)2D3 and 20(OH)D3 inhibited the expression of GLI1 and β‑catenin in ASZ001 cells. In A431 cells, these compounds also decreased the expression of GLI1 and stimulated involucrin expression. VDR, RORγ, RORα and CYP27B1 were detected in A431, SCC13 and ASZ001 lines, however, with different expression patterns. Immunohistochemistry performed on human skin with SCC and BCC showed nuclear expression of all three of these receptors, as well as megalin (transmembrane receptor for vitamin D‑binding protein), the level of which was dependent on the type of cancer and antigen tested in comparison with normal epidermis. Classical and CYP11A1‑derived vitamin D3‑derivatives exhibited anticancer‑activities on skin cancer cell lines and inhibited GLI1 and β‑catenin signaling in a manner that was dependent on the position of hydroxyl groups. The observed expression of VDR, RORγ, RORα and megalin in human SCC and BCC suggested that they might provide targets for endogenously produced or exogenously applied vitamin D hydroxyderivatives and provide excellent candidates for anti‑cancer therapy.

New non-peptide endothelin-A receptor antagonists: synthesis, biological properties, and structure-activity relationships of 5-(dimethylamino)-N-pyridyl-,-N-pyrimidinyl-,-N-pyridazinyl-, and -N-pyrazinyl-1-naphthalenesulfonamides

Use of automated synthesis led to the discovery of several 6-membered nitrogen heterocycles as replacements for the N-isoxazolyl substituent present in the 1-naphthalenesulfonamides endothelin-A (ETA) antagonist 5-(dimethylamino)-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesu lfo namides (BMS 182874). In each of these heterocycles, a small substituent such as halogen para to the position of attachment to the sulfonamide nitrogen atom was found to be advantageous for ETA receptor affinity. Of these heterocycles, 2-pyrazines offered the greatest scope for improving receptor affinity. Optimization of the substituents at the 3- and 5-positions in the pyrazine ring led to potent, ETA-selective compounds such as 5-(dimethylamino)-N-(5-chloro-3-methoxy-2-pyrazinyl)-1- naphthalenesulfonamides (7m, ETA pIC50 8.1). When dosed orally at 10 mg/kg to conscious, normotensive rats infused with big ET-1, compounds such as 7m showed significant inhibition of the pressor response with a duration of effect lasting for the 5-h course of the experiment.

Cell-based assay for functional screening of compounds active at the human endothelin A receptor

We have developed a cell based assay for the functional screening of chemical libraries for novel chemical entities active at the human endothelin A (ET(A)) receptor. The assay is relatively inexpensive, suitable for dealing with large number of samples, and simple to operate; it generates results quickly. We achieved this by expressing the cDNA for the receptor in mammalian cell lines and determining whether coupling to pIA(A) occurred through the quantification of released radiolabeled arachidonic acid (AA) into the culture medium. Significant coupling was observed only when the receptor was expressed in the Chinese hamster ovary (CHO) line DG44. The assay could distinguish between ET(A)r agonists and antagonists, and the IC50 (the concentration that inhibits maximum response by 50%) values obtained were similar to those from other sources of receptor. The ET(B) receptor-selective agonist BQ3020 did not stimulate AA release, indicating that the assay can also discriminate between receptor subtypes.

Structural features of tracheal tube biofilm formed during prolonged mechanical ventilation

The dissemination of tracheal tube biofilm into the mechanically ventilated lung has been proposed as a contributory factor in the pathogenesis of ventilator-associated pneumonia. In the present study, conventional light microscopy, confocal laser scanning microscopy, and scanning electron microscopy were used to examine luminal tracheal tube biofilm in tubes from ten consecutive medical intensive care patients. Biofilms also were cultured. No tube contained a predominantly microbial aggregate. Microorganisms were either dispersed throughout the biofilm or restricted to the most superficial layer. Neutrophil polymorphonuclear cells were present in all biofilms in a pattern suggesting that a layering or stratification had taken place. The distribution of neutrophils and microorganisms was consistent with a progressive accretion of respiratory secretions, rather than formation of a predominantly microbial biofilm.

Cytoskeletal proteolysis during calcium-induced morphological transitions of human erythrocytes

An analysis was made of the rate, extent, and reversibility of the morphological transitions which were induced in human erythrocytes after loading with 150 microM or 1 mM Ca2+. The rate and extent of proteolytic cleavage of cytoskeletal proteins were monitored simultaneously, particularly those of the ankyrins and band 4.1, and were found not to reflect the rate of shape change. These observations were made when intact cells were incubated either in a buffer which supported glycolysis or in a simple isotonic Tris buffer without glucose. The composition of the buffer affected the initial morphology of the cells, the rate of morphological transition, the rate of proteolysis of cytoskeletal proteins, and the extent and kinetics of the reversal of morphology from the echinocyte to discocyte after removal of the ionophore A23187 and Ca2+. The morphology of cells transformed to spheroechinocytes by loading metabolically depleted cells for 15 min with 1 mM Ca2+, and which retained 50% band 2.1, was reversed in the presence of substrates for ATP synthesis to that of a mixture of 60% stage 1 echinocytes plus 25% discocytes, suggesting that ankyrin may not be essential for the maintenance of a disc-like morphology. Echinocytes which were depleted of greater than 50% band 4.1 were unable to undergo the transition back to discs.

Glucagon, vasopressin and angiotensin all elicit a rapid, transient increase in hepatocyte protein kinase C activity

Challenge of intact hepatocytes with one of the hormones vasopressin, angiotensin and glucagon or with the phorbol ester phorbol 12-myristate 13-acetate (PMA) led to a rapid increase in the activity of protein kinase C found in both cytosol and membrane fractions. Maximal activation by hormones occurred within 1-6 min of challenge of cells, after which activity declined. In membrane fractions protein kinase C activity return to basal levels some 15 min after exposure of cells to either angiotensin or glucagon. In cytosol fractions of cells challenged with hormones a second phase of activation ensued after about 10 min, with levels of protein kinase C activity remaining elevated above basal level 15 min afterwards. Activity changes elicited by PMA were rather different; it took about 15 min to achieve maximal activation of cytosolic protein kinase C activity. In membranes of cells challenged with PMA, an initial rapid and transient activation was followed by a sustained increase in activity occurring about 10 min after exposure of cells to this ligand. Only when hepatocytes were challenged with PMA was the translocation of protein kinase C from the cytosol to membrane fraction observed. The kinetics of PMA-induced translocation suggested that it accounted for the second phase of the increase in membrane protein kinase C activity which was unique to this ligand.

Identification of two cAMP-dependent phosphorylation sites on erythrocyte protein 4.1

In human erythrocytes, dibutyryl cyclic AMP induces the phosphorylation of protein 4.1 on sites within the adjacent 16 kDa and 10 kDa chymotryptic domains (Horne, W.C., Leto, T.L. and Marchesi, V.T. (1985) J. Biol. Chem. 260, 9073-9076). The 10 kDa domain also contains the spectrin/actin-binding site (Correas, I., Leto, T.L., Speicher, D.W. and Marchesi, V.T. (1986) J. Biol. Chem. 261, 3310-3315) and it has been shown that phosphorylation of protein 4.1 by cyclic AMP-dependent protein kinase inhibits the binding of protein 4.1 to spectrin and actin (Ling, E., Danilov, Y.N. and Cohen, C.M. (1988) J. Biol. Chem. 263, 2209-2216). In this study, we have identified two sites on protein 4.1 which account for 80% of the phosphate incorporated into protein 4.1 during metabolic labelling of erythrocytes in the presence of dibutyryl cyclic AMP. More than 95% of the 32P incorporated into protein 4.1 was in the form of phosphoserine. Reverse-phase HPLC of the peptides generated by digestion of the isolated protein with trypsin or endoproteinase lysine C produced two major radioactive peaks. The phosphorylation sites, identified by gas phase sequencing of the purified phosphopeptides and confirmed by determining the residues converted to S-ethylcysteine by reacting the phosphopeptides with ethanethiol under alkaline conditions, were Ser-331, in the 16 kDa domain and Ser-467, in the 10 kDa domain.

Metabolism of D-myo-inositol 1,3,4,5-tetrakisphosphate by rat liver, including the synthesis of a novel isomer of myo-inositol tetrakisphosphate

1. We have studied the metabolism of Ins(1,3,4,5)P4 (inositol 1,3,4,5-tetrakisphosphate) by rat liver homogenates incubated in a medium resembling intracellular ionic strength and pH. 2. Ins(1,3,4,5)P4 was dephosphorylated to a single inositol trisphosphate product, Ins(1,3,4)P3 (inositol 1,3,4-trisphosphate), the identity of which was confirmed by periodate degradation, followed by reduction and dephosphorylation to yield altritol. 3. The major InsP2 (inositol bisphosphate) product was inositol 3,4-bisphosphate [Shears, Storey, Morris, Cubitt, Parry, Michell & Kirk (1987) Biochem. J. 242, 393-402]. Small quantities of a second InsP2 product was also detected in some experiments, but its isomeric configuration was not identified. 4. The Ins(1,3,4,5)P4 5-phosphatase activity was primarily associated with plasma membranes. 5. ATP (5 mM) decreased the membrane-associated Ins(1,4,5)P3 5-phosphatase and Ins(1,3,4,5)P4 5-phosphatase activities by 40-50%. This inhibition was imitated by AMP, adenosine 5'-[beta gamma-imido]triphosphate, adenosine 5'-[gamma-thio]triphosphate or PPi, but not by adenosine or Pi. A decrease in [ATP] from 7 to 3 mM halved the inhibition of Ins(1,3,4,5)P4 5-phosphatase activity, but the extent of inhibition was not further decreased unless [ATP] less than 0.1 mM. 6. Ins(1,3,4,5)P4 5-phosphatase was insensitive to 50 mM-Li+, but was inhibited by 5 mM-2,3-bisphosphoglycerate. 7. The Ins(1,3,4,5)P4 5-phosphatase activity was unchanged by cyclic AMP, GTP, guanosine 5'-[beta gamma-imido]triphosphate or guanosine 5'-[gamma-thio]triphosphate, or by increasing [Ca2+] from 0.1 to 1 microM. 8. Ins(1,3,4)P3 was phosphorylated in an ATP-dependent manner to an isomer of InsP4 that was partially separable on h.p.l.c. from Ins(1,3,4,5)P4. The novel InsP4 appears to be Ins(1,3,4,6)P4. Its metabolic fate and function are not known.