Anti-tumorigenic action of 2-[piperidinoethoxyphenyl]-3-[4-hydroxyphenyl]-2H-benzo(b)pyran: evidence for involvement of GPR30/EGFR signaling pathway.

OBJECTIVE: The aim of the present study was to investigate the effect of non-steroidal, pure antiestrogenic benzopyran derivative i.e., 2-[piperidinoethoxyphenyl]-3-[4-hydroxyphenyl]-2H-benzo(b)pyran (K-1) on the growth of human endometrial cancer cells in vivo and in vitro and to elucidate its mechanism of action. METHODS: Cell proliferation was assayed by measuring the incorporation of 5'-bromo-2'-deoxyuridine in Ishikawa and primary endometrial cancer cells. The expression of proliferation and apoptotic markers was analyzed by immunoblotting. The effect of K-1 on GPR30-regulated proteins was analyzed by ELISA and by immunoblotting. Nude mice bearing subcutaneous implanted-Ishikawa tumors, were treated for 14days with K-1 (200µg/kg body weight/day/orally). The proliferation markers, GPR30-regulated proteins and apoptotic markers were analyzed by immunoblotting in tumor xenograft. The apoptotic effect of compound K-1 was determined by TUNEL assay. RESULTS: Compound K-1 inhibited proliferation of endometrial adenocarcinoma cells and decreased the expression of proliferation markers. It caused apoptosis by increasing the expression of apoptotic markers (NOXA, PUMAα) and reducing the expression of p-CREB and BclxL. Compound interfered with GPR30-regulated-EGFR activation, decreased p-ERK, p-c-jun, c-fos, cyclinD1 and c-myc expression. Treatment of tumor-bearing mice with K-1 resulted in a significant decrease in tumor volume and weight. Decreased expression of p-ERK and its downstream molecules and increased expression of apoptotic markers were observed in tumor in K-1 treated animals. CONCLUSION: Findings suggest the potent inhibitory effect of compound K-1 on endometrial cancer cellular growth (in-vitro) and on tumor size (in-vivo) which is mediated at least, in part, by interference with GPR30-signaling.

Lack of genetic association of promoter and structural variants of mannan-binding lectin (MBL2) gene with susceptibility to generalized vitiligo.

BACKGROUND: Vitiligo is a common depigmenting disorder resulting from the loss of functional melanocytes in the skin. It is hypothesized to be of autoimmune origin. Mannan-binding lectin (MBL) plays an important role in innate immunity. It helps in the clearance of apoptotic cells and in complement activation. Genetic variability due to structural and promoter polymorphisms in the MBL2 gene has been reported to be associated with increased risk for several autoimmune diseases including vitiligo. OBJECTIVES: The aim of this study was to explore whether MBL2 structural and promoter polymorphisms are associated with generalized vitiligo in Gujarat where the prevalence of vitiligo is alarmingly high. MATERIALS AND METHODS: We undertook a case-control study to investigate the association of MBL2 gene exon 1 polymorphisms - codon 52, codon 54 and codon 57 as well as promoter -221 polymorphism in 92 patients with generalized vitiligo and 94 unaffected age-matched controls by polymerase chain reaction-heteroduplex analysis. RESULTS: The genotype and allele frequencies of MBL2 structural and promoter polymorphisms did not differ significantly between the control and patient population (P-values: P < 0.019 for codon 52, P < 0.373 for codon 54, P < 0.855 for codon 57 and P < 0.889 for -221 promoter polymorphisms) after Bonferroni's correction for multiple testing, which suggests that there is no association of MBL2 structural and promoter polymorphisms with generalized vitiligo. CONCLUSIONS: Our results suggest that the well-documented structural and promoter polymorphisms of the MBL2 gene may not be associated with generalized vitiligo in the Gujarat population.

Synthesis and biological evaluation of 3,4,6-triaryl-2-pyranones as a potential new class of anti-breast cancer agents.

A series of 3,4,6-triaryl-2-pyranones, new class of anti-breast cancer agents, have been synthesized as a structural variants of cyclic triphenylethylenes by replacing the fused benzene ring with pendant phenyl ring to mimic the phenolic A ring of estradiol. Nine of these newly synthesized pyranones exhibited significant anti-proliferative activity in both ER+ve and ER-ve breast cancer cell lines. Four active non-cytotoxic compounds 5c, 5d, 5g and 5h showed specific and selective cytotoxicity and two compounds 5d and 5h induced significant DNA fragmentation in both MCF-7 and MDA-MB-231 cell lines. Based on RBA studies, the molecules probably act in an ER-independent mechanism. The involved pathway was observed as caspase-dependant apoptosis in MCF-7 cells. However, the particular caspases involved and the possible cellular target through which this series of compounds mediate cell death are not known.

Synthesis and biological evaluation of indolyl bisphosphonates as anti-bone resorptive and anti-leishmanial agents.

A series of indole conjugated bisphosphonate derivatives have been synthesized and evaluated for their in vitro anti-bone resorptive activity using bone marrow osteoclast culture. Two bisphosphonates 23 and 24 significantly inhibited osteoclastogenesis, 23 showed inhibition at 10 and 100 pM which was lower than the concentration of standard drug alendronate, and 24 inhibited osteoclastogenesis at 100 nM which was comparable to alendronate. Two other compounds 13 and 14 also showed inhibition comparable to alendronate, but were cytotoxic in the osteoblast cells. The two active bisphosphonates 23 and 24 induced significant osteoclast apoptosis at concentrations 100 nM for compound 24 and at 10 pM for compound 23 compared to alendronate. In vivo effect of active bisphosphonates 23 and 24 resulted in osteoclastogenesis of bone marrow cells (BMCs) to almost 40-50% (23 showing 8.4% decrease and 24 showing 9.0%) compared to 16.5% of the ovariectomized group. Further, screening of anti-leishmanial activity, four compounds 24-25 and 27-28 showed more than 80% inhibition against both the promastigote and amastigote stages of the Leishmania parasite.

Synthesis and structure guided evaluation of estrogen agonist and antagonist activities of some new tetrazolyl indole derivatives.

Several regioisomeric tetrazolyl indole derivatives with structurally modified alkyl substituents at the tetracyclic indole nitrogen containing N-ethyl amino tetrazole moiety have been synthesized and screened for their ER binding affinity, agonist (estrogenic), antagonist (antiestrogenic) and anti-implantation activities. N-2 regioisomers were found to be moderately antagonists and one compound showed 100% contraceptive efficacy at 10 mg/kg dose. Molecular docking studies carried out in comparison to estradiol and raloxifene showed different binding modes of the two regioisomers to the binding site.

New piperidine derivative DTPEP acts as dual-acting anti-breast cancer agent by targeting ERα and downregulating PI3K/Akt-PKCα leading to caspase-dependent apoptosis.

OBJECTIVES: In our ongoing studies to develop ER targeting agents, we screened for dual-acting molecules with a hypothesis that a single molecule can also target both ER positive and negative groups of breast cancer. MATERIALS AND METHODS: 1-(2-(4-(Dibenzo[b,f]thiepin-10-yl)phenoxy)ethyl)piperidine (DTPEP) was synthesized and screened in both MCF-7 (ER+ve) and MDA-MB-231 (ER-ve) cells. Assays for analysis of cell cycle, ROS, apoptosis and MMP loss were carried out using flow cytometry. Its target was investigated using western blot, transactivation assay and RT-PCR. In vivo efficacy of DTPEP was validated in LA-7 syngeneic rat mammary tumour model. RESULTS: Here, we report identification of dual-acting molecule DTPEP that downregualtes PI3K/Akt and PKCα expression, induces ROS and ROS-dependent apoptosis, loss of mitochondrial membrane potential, induces expression of caspase indicative of both intrinsic and extrinsic apoptosis in MCF-7 and MDA-MB-231 cells. In MCF-7 cells, DTPEP downregulates ERα expression and activation. In MDA-MB-231 cells, primary cellular target of DTPEP is not clearly known, but it downregualtes PI3K/Akt and PKCα expression. In vivo study showed regression of LA-7 syngeneic mammary tumour in SD rat. CONCLUSIONS: We identified a new dual-acting anti-breast cancer molecules as a proof of concept which is capable of targeting both ER-positive and ER-negative breast cancer.

Collectins and host defence.

The collectins are a small family of soluble oligomeric proteins containing collagenous regions and C-type lectin domains. They are related in structure and function to complement protein C1q, and to H-, L- and M-ficolins. In humans, the collectins mannose-binding lectin (MBL) and surfactant proteins A and D (SP-A, SP-D) have important roles in innate immunity. MBL occurs mainly in blood plasma and in the upper respiratory tract. It binds to neutral sugar arrays on microorganisms and acts as an opsonin either directly (by binding to cell-surface calreticulin) or indirectly by activating complement. MBL circulates in complex with any of three proteases, named MBL-associated serine proteases (MASPs)-1, -2 and -3. MBL-MASP-2 complexes activate complement, but the role of MBL-MASP-1 and MBL-MASP-3 complexes is not yet known. MBL deficiency occurs at high frequency, and is associated with susceptibility to infection, particularly in infants. SP-A and SP-D are most abundant in the lungs, and also bind to microorganisms and inhaled particulates, mainly by lectin-sugar interactions. They do not activate complement, but act as opsonins and agglutinators, and have additional effects on cellular regulation. Mice deficient in SP-A or SP-D are susceptible to lung infections, and SP-D-deficient mice develop an emphysema-like condition.

Development of a fluorescence assay for the detection of L-ficolin-MASP in serum or purified samples.

A fluorescence assay for the detection of L-ficolin-MASP in human serum or purified sample was developed by measuring the cleavage of fluorescent amide substrate by L-ficolin associated MASPs bound to the lipoteichoic acid (LTA). LTA (Staphylococcus aureus DSM 20233) was coated on NuncMaxisorp microtiter plates and serum or purified sample incubated overnight at 4 degrees C to allow the L-ficolin-MASP to bind LTA. Assay conditions for binding and complete cleavage of fluorescent amide substrate were standardized. The optimum temperature, incubation time and molarity of NaCl for LTA-ficolin binding were found to be 4 degrees C for 6 h at 1 M NaCl concentration. The optimum incubation time and pH for complete cleavage of fluorescent amide substrate by LTA bound L-ficolin associated MASP were found to be 2 h at pH 8.5. LTA-ficolin binding was found to be highly specific and was inhibited completely by LTA but not with mannose. A calibration curve was prepared by using the purified ficolin-MASP complex (1 to 12 mug/ml) and could be used to find concentration of ficolin-MASP complex in normal human serum.

Studies on metal induced conformation changes in a peripheral blood lymphocyte lectin.

A Ca2+ -dependent, glucose-specific lectin was isolated from goat peripheral blood lymphocytes by affinity chromatography on N-acetyl D-glucosamine agarose gel. Since the lectin binding to carbohydrate ligands was metal dependent, it was important to study the divalent metal ion-induced conformational changes in the lectin. The conformational changes were studied by absorption, fluorescence and circular dichroism spectroscopy techniques. Binding of Ca2+, Mn2+ or Mg2+ results in shift in ultraviolet absorption maxima from 281 to 298 nm (red shift). A major increase in absorbance at 245 nm is also exhibited. Binding of Ca2+ and Mn2+ resulted in decrease in intrinsic fluorescence emission maxima with shift from 355.2 nm to 342.4 nm (blue shift). These shifts could be reversed on addition of EDTA. A double reciprocal analysis of fluorescence quenching data suggest that Ca2+ and Mn2+ interact with a single class of binding site with an apparent kd of 1.50 +/- 0.37 microM and 1.25 +/- 0.25 microM, respectively. These data clearly indicate that occupancy of metal binding sites on goat peripheral blood lymphocyte lectin induces a gross conformational change sequestering aromatic amino acids into a hydrophobic environment. These findings were further supported by circular dichroism spectrum which showed a massive alteration in the presence of Ca2+.

Carbohydrate-induced modulation of cell membrane--III. Interaction of sialic acid and mannose with hamster splenic lymphocytes: a spin label study.

The role of different carbohydrates as ligands for adhesion molecules has been extensively studied. However, the physiological changes in the splenic lymphocytes on binding these ligands have never been studied. In this paper, we report that binding of sialic acid or mannose to hamster splenic lymphocytes restricts the mobility of membrane proteins and lipids as studied by EPR spectroscopy using spin probes. Binding of mucin and heparin totally restricts the mobility probably due to crosslinking of the surface lectins. Binding of these ligands also results in an increase in the viscosity of the cytoplasm.

Electron spin resonance study of the metal binding site of glucose specific peripheral blood lymphocyte lectin.

The electron spin resonance (ESR) spectrum of Mn2+ is highly responsive to changes in coordination symmetry. We have thus used ESR spectroscopy to study Mn2+ bound to goat peripheral blood lymphocyte lectin to delineate the nature of the metal binding site of the lectin. Our results suggest the presence of two metal binding sites on goat peripheral blood lymphocyte lectin, one a dissociable site which could bind Cu2+, Ca2+, Mg2+ and Ni2+ to displace bound Mn2+ and the other a non-dissociable site from which bound Mn2+ could not be displaced. Since no spectral changes are observed when D-glucose is bound, it is unlikely that Mn2+ participates directly in saccharide binding.

Synthesis of targeted dibenzo[b,f]thiepines and dibenzo[b,f]oxepines as potential lead molecules with promising anti-breast cancer activity.

A targeted library of substituted dibenzo[b,f]thiepines and dibenzo[b,f]oxepines (prototypes I, II and III), and structurally analogous to tamoxifen have been synthesized as a new class of anti-breast cancer agents. All the prototype molecules exhibited potential antiproliferative activity against ER + ve and ER-ve breast cancer cell lines. Dibenzo[b,f]thiepine prototypes were found to be more active. Of all the compound tested, 14b exhibited potent in-vitro antiproliferative activity at 1.33 µM and 5 µM concentration in MCF-7 and MDA-MB-231 cell lines and was devoid of any cytotoxicity in normal HEK cells even at 50 µM. Cell cycle analysis showed that the compound 14b inhibited cell proliferation due to G0/G1 arrest in MCF-7 cells. Annexin-V FITC and PI staining experiments confirmed that the cell inhibition was primarily due to apoptosis and not by necrosis, which was also supported by LDH release assay experiment. Molecular docking studies showed better binding interaction of the new dibenzo[b,f]thiepine analogue 14b with the estrogen receptor (ER) as compared to 4-hydroxy-tamoxifen and this enhanced binding might be responsible for its estrogen antagonistic activity that induces cell cycle arrest, apoptosis and inhibition of breast cancer cells.

Carbohydrate induced modulation of cell membrane: II. Spin label study of fluidity changes in peripheral blood lymphocyte membrane.

This paper reports for the first time, that binding of various mono-, di-, and trisaccharides to membrane lectins reduces the rotational motion of membrane proteins and lipids indicating a decrease in membrane fluidity as studied by EPR spectroscopy using spin probes. Interaction of polysaccharides with lymphocyte resulted in an extensive decrease in membrane fluidity making the membrane almost rigid. The decrease in fluidity was dose-dependent, dependent on the multivalency of the ligand used, and was sensitive to presence of EDTA and sodium azide. Binding of two different carbohydrate ligands on their respective surface lectins has a synergistic effect on the decrease in membrane fluidity.

ESR studies on the effect of ionic radii on displacement of Mn2+ bound to a soluble beta-galactoside binding hepatic lectin.

Binding of divalent metal ions to hepatic soluble beta-galactoside binding lectin was studied using electron spin resonance (ESR) spectroscopy. The Mn2+ bound to hepatic lectin could be displaced by Mg2+, Cu2+, Ni2+ and Ca2+ but not by Sr2+. As the ionic radii of Mg2+ (0.65 A), Cu2+ (0.73 A) and Ni2+ (0.72 A) are appreciably smaller than Ca2+ (0.99 A), it appears that the Mn2+ binding site is more accessible to Mg2+, Cu2+, and Ni2+ as compared to Ca2+, the ionic radius of Mn2+ being 0.80 A. Sr2+ with an ionic radius of 1.13 is thus unable to displace bound Mn2+. Surprisingly, the presence of specific sugars like alpha-lactose, or alpha-D-galactose facilitated the displacement of bound Mn2+ by metal ions whereas non-specific sugars, i.e. alpha-D-glucose, beta-D-fructose and alpha-D-ribose had no effect. It appears that minor perturbations in the saccharide binding site significantly affect the ability of the metal binding site to ligate bivalent metals.

Carbohydrate induced modulation of cell membrane. I. Interaction of sialic acid with peripheral blood lymphocytes: a spin label study.

Sialic acid is now known to serve as ligand for lymphocyte lectins known as selectins. Although its role as a ligand for adhesion molecules has been studied extensively, no studies have been performed to determine the physiological changes in lymphocytes after binding of sialic acid to lymphocyte lectin. We report for the first time that interaction of lymphocytes with sialic acid severely restricts the rotational mobility of the cell surface proteins as well as membrane lipids, as studied by EPR spectroscopy using spin probes. Binding of mucin totally immobilizes the lymphocyte membrane. Surprisingly the binding of sialic acid or mucin also immobilized the aqueous probe TEMPO, indicating an appreciable increase in cytoplasmic viscosity.

Carbohydrate induced modulation of cell membrane. VI. Binding of exogenous lectin induces susceptibility of erythrocytes to free radical damage: a spin label study.

The oxidation of erythrocyte membrane has been widely used as a model to study the damage of biomembranes by free radicals. Whether binding of lectin to erythrocytes has any effect on peroxidant injury has never been studied. This study reports for the first time that crosslinking of erythrocyte surface glycoprotein by an exogenous lectin significantly enhances the susceptibility to membrane damage by free radicals, as evidenced by the increase in membrane fluidity measured by EPR using spin label and the increase in the amount of oxyhemoglobin liberated due to cell lysis.

Carbohydrate induced modulation of cell membrane VII. Binding of exogenous lectin increases osmofragility of erythrocytes.

Due to their multivalent binding character, lectins when added exogenously will cross-link membrane surface receptors leading to lateral molecular reorganizations in the plane of the bilayer. This study reports for the first time that agglutination of rabbit erythrocytes by lentil lectin and concanavalin A increases their osmofragility. Increase in osmofragility was detected by measuring the hemolysis of erythrocytes in hypotonic as well as in isotonic solutions. It was also found that agglutination per se does not increase osmofragility but the binding of legume lectin is essential since human Rh+ cells agglutinated by a monoclonal antibody do not exhibit hemolysis.

Were lectins primitive Fc receptors?

Co-operation between humoral and cellular pathways occurs by the interaction of antibody antigen complexes with effector cells. This interaction is mediated by receptors for the Fc region of antibody, Fc receptors (FcR). Molecular characterisation of low-affinity receptors for IgE revealed an 123-amino-acid domain homologous with the carbohydrate-binding domain of the C-type animal lectins. Although IgE is heavily glycosylated, the binding of Fc epsilon RII to IgE was found to be independent of any "lectin-like" activity. The presence on lymphoid cells of a family of adhesion molecules containing a lectin-like domain, the ability of these lectin-like molecules and surface lectins to bind immunoglobulins, and subsequently the role of carbohydrates in the binding of immunoglobulins to such surface molecules imply that the ancestral carbohydrate. recognition domain of lectins held together by conserved cystein residues has evolved as FcR to recognise the constant region of immunoglobulins.

Binding of immunoglobulin G to peripheral blood lymphocytes.

The specific and saturable binding of FITC conjugate of aggregated goat IgG to goat peripheral blood lymphocytes was studied in PBS containing 1% BSA. The polar nature of the specific interaction of heterologous aggregated IgG, IgG monomer and its fragment F(ab'2) with the cells was studied by ELISA using the peroxidase conjugated F(ab'2) of anti-human IgG under different conditions of pH and ionic strength.

Studies on a glucose-binding lectin from peripheral blood lymphocytes.

Lectin-carbohydrate interactions have been found to be important in many of the steps of lymphocyte recirculation and inflammatory responses. A D-glucose-specific lectin was isolated from goat peripheral blood lymphocytes by affinity chromatography on N-acetyl-D-glucosamine agarose and gave a single band corresponding to 112 kDa in SDS-PAGE, irrespective of treatment with 2-mercaptoethanol. The lymphocyte lectin agglutinated rabbit and human ABO erythrocytes, the hemagglutinating activity being Ca2+ dependent. It appears to be a member of type C animal lectins.