Melanoma cases demonstrate increased carrier frequency of phenylketonuria/hyperphenylalanemia mutations

Identifying novel melanoma genetic risk factors informs screening and prevention efforts. Mutations in the phenylalanine hydroxylase gene (the causative gene in phenylketonuria) lead to reduced pigmentation in untreated phenylketonuria patients, and reduced pigmentation is associated with greater melanoma risk. Therefore, we sought to characterize the relationship between phenylketonuria carrier status and melanoma risk. Using National Newborn Screening Reports, we determined the United States phenylketonuria/hyperphenylalanemia carrier frequency in Caucasians to be 1.76%. We examined three publically available melanoma datasets for germline mutations in the phenylalanine hydroxylase gene associated with classic phenylketonuria and/or hyperphenylalanemia. Mutations were identified in 29/814 melanoma patients, with a carrier frequency of 3.56%. There was a twofold enrichment (p ‐value = 3.4 × 10^?5) compared to the Caucasian frequency of hyperphenylalanemia/phenylketonuria carriers. These data demonstrate a novel association between phenylalanine hydroxylase carrier status and melanoma risk. Further, functional investigation is warranted to determine the link between phenylalanine hydroxylase mutations and melanomagenesis.     

Intrinsic properties and regulation of Pannexin 1 channel

Pannexin 1 (Panx1) channels are generally represented as non-selective, large-pore channels that release ATP. Emerging roles have been described for Panx1 in mediating purinergic signaling in the normal nervous, cardiovascular, and immune systems, where they may be activated by mechanical stress, ionotropic and metabotropic receptor signaling, and via proteolytic cleavage of the Panx1 C-terminus. Panx1 channels are widely expressed in various cell types, and it is now thought that targeting these channels therapeutically may be beneficial in a number of pathophysiological contexts, such as asthma, atherosclerosis, hypertension, and ischemic-induced seizures. Even as interest in Panx1 channels is burgeoning, some of their basic properties, mechanisms of modulation, and proposed functions remain controversial, with recent reports challenging some long-held views regarding Panx1 channels. In this brief review, we summarize some well-established features of Panx1 channels; we then address some current confounding issues surrounding Panx1 channels, especially with respect to intrinsic channel properties, in order to raise awareness of these unsettled issues for future research.     

Alterations in the heart lysosomal stability in isoproterenol induced myocardial infarction in rats

The alterations in the heart lysosomal stability following isoproterenol induced myocardial infarction were studied in albino rats. The rate of release of beta-glucuronidase at various time intervals at 37 degrees C from lysosome rich fraction was taken as a measure of lysosomal stability. As compared to the control day one, three and five samples exhibited a significant increase in beta-glucuronidase activity at all the time intervals. The subcellular distribution of beta-glucuronidase was also studied and the soluble and total activities exhibited an increase at peak infarction stage and returned to normal during the recovery. The decrease in the lysosomal stability might be attributed to the increased beta-glucuronidase activity observed following myocardial infarction.     

Hepatoprotective effect of Rhodiola imbricata rhizome against paracetamol-induced liver toxicity in rats

Rhodiola imbricata is a perennial herb of the family Crassulaceae, which has significant traditional usage as medicine and is also known to biosynthesize phytochemicals such as flavonoids, coumarins and phenyl glycosides. The present investigation was aimed to estimate the hepatoprotective activity of R. imbricata rhizome acetone extract against paracetamol (2 g/kg) induced liver toxicity. Paracetamol was administered to induce hepatic damage in Wistar rats. 200 and 400 mg/kg doses of rhizome acetone extract and silymarin (25 mg/kg) were used as treatment groups. The blood samples were analyzed for biochemical markers of hepatic injury and tissue samples were subjected for estimation of liver antioxidants and histopathological studies. Analysis of the extract treated rats (400 mg/kg) showed an elevation of superoxide dismutase (0.326 units/min/mg protein), catalase (185.03 μmole of H₂O₂ consumed/min/mg protein), glutothione peroxidase (19.26 mg GSH consumed/min/mg protein) and reduced glutathione (16.2 μmole of GSH/mg protein). Moreover, the biochemical parameters in serum like alkaline phosphatase, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT) and lipid profiles were also improved in treated groups compared to the control. The oral administration of different doses of rhizome acetone extract significantly protected the hepatic cells from damage. The hematological and biochemical parameters were also normal in extract treated rats compared to the control and standard (silymarin) groups. The HPLC analysis revealed the presence of some important phenolic compounds which could be responsible for the hepatoprotective activity. This study proved that R. imbricata could be taken as a good natural source of the hepatoprotective agent.     

A requirement for lipid rafts in B cell receptor induced Ca(2+) flux

Although the major biochemical events triggered by ligation of the B-cell receptor (BCR) have been well defined [1] [2], little is known about the spatio-temporal organization of BCR signaling components within the cell membrane and the mechanisms by which signaling specificity is achieved. Partitioning of signaling complexes into specialized domains in the plasma membrane may provide a mechanism for channeling specific stimuli into distinct signaling pathways. Here, we report that multiple tyrosine-phosphorylated proteins accumulate transiently upon BCR activation in detergent-insoluble membrane microdomains known as lipid rafts. We found an activation-dependent translocation to the rafts of the BCR itself, as well as phospholipase Cgamma2 (PLCgamma2), an enzyme critical for BCR-induced Ca(2+) flux in B cells. An intact raft structure was required for BCR-induced tyrosine phosphorylation of PLCgamma2 and the induction of Ca(2+) flux. Taken together, these data provide a functional role for lipid rafts in BCR signaling.     

Regulation of the Src Homology 2 Domain-containing Inositol 5��-Phosphatase (SHIP1) by the Cyclic AMP-dependent Protein Kinase

Many agents that activate hematopoietic cells use phos pha tidyl ino si tol 3,4,5-trisphosphate (PtdIns 3,4,5-P₃) to initiate signaling cascades. The SH2 domain-containing inositol 5′ phosphatase, SHIP1, regulates hematopoietic cell function by opposing the action of phos pha tidyl ino si tol 3-kinase and reducing the levels of PtdIns 3,4,5-P₃. Activation of the cyclic AMP-de pend ent protein kinase (PKA) also opposes many of the pro-inflammatory responses of hematopoietic cells. We tested to see whether the activity of SHIP1 was regulated via phos pho ryl a tion with PKA. We prepared pure recombinant SHIP1 from HEK-293 cells and found it can be rapidly phos pho ryl a ted by PKA to a stoichiometry of 0.6 mol of PO₄/mol of SHIP1. In ³²P-labeled HEK-293 cells transfected with SHIP1, stimulation with Sp-adenosine 3′,5′-cyclic monophosphorothioate triethylammonium salt hydrate (Sp-cAMPS) or activation of the β-adrenergic receptor increased the phos pho ryl a tion state of SHIP1. Inhibition of protein phosphatase activity with okadaic acid also increased the phos pho ryl a tion of SHIP1. Phosphorylation of SHIP1 in vitro or in cells by PKA increased the 5′ phosphatase activity of SHIP1 by 2–3-fold. Elevation of Ca²⁺ in DT40 cells in response to B cell receptor cross-linking, an indicator of PtdIns 3,4,5-P₃ levels, was markedly blunted by pretreatment with Sp-cAMPS. This effect was absent in SHIP^−/− DT40 cells showing that the effect of Sp-cAMPS in DT40 cells is SHIP1-de pend ent. Sp-cAMPS also blunted the ability of the B cell receptor to increase the phos pho ryl a tion of Akt in DT40 and A20 cells. Overall, activation of G protein-coupled receptors that raise cyclic AMP cause SHIP1 to be phos pho ryl a ted and stimulate its inositol phosphatase activity. These results outline a novel mechanism of SHIP1 regulation.Activation of phosphatidylinositol 3-kinase (PtdIns 3-kinase)² is central to regulation of multiple cell functions including cell shape changes, cell migration, cell activation, and proliferation (1). PtdIns 3-kinase phosphorylates phosphatidylinositol 4,5-bisphosphate in the inner leaflet of the plasma membrane to generate phosphatidylinositol 3,4,5-trisphosphate (PtdIns 3,4,5-P₃) (2). PtdIns 3,4,5-P₃ then activates downstream signaling pathways by interacting with pleckstrin homology domain-containing proteins, such as phosphoinositide-dependent kinase 1 and the serine-threonine kinase Akt (3). The finding of abnormal activation of the PtdIns 3-kinase pathway in cancer cells has led to interest in the development of inhibitors for PtdIns 3-kinase (4).The level of PtdIns 3,4,5-P₃ is stimulated by multiple members of the PtdIns 3-kinase family (2) and is opposed by two phosphatidylinositol phosphatases: the Src homology 2 (SH2) domain-containing inositol 5′ phosphatase (SHIP) and the 3′ inositol phosphatase, phosphatase and tensin homolog (PTEN) (5). PTEN removes phosphate from the 3′ position in the inositol ring of PtdIns 3,4,5-P₃ and converts it to phosphatidylinositol 4,5-bisphosphate (6). PTEN has a C2 domain, a PDZ-binding motif, and a N-terminal phosphatidylinositol 4,5-bisphosphate binding motif essential for translocation to the membrane and interaction with other regulatory proteins (7). There are serine and threonine residues in PTEN that have been found to be phosphorylated, but their role in regulating the activity of the enzyme is not clear (8). Mutations in the PTEN protein have been observed in many tumors, suggesting a role for this enzyme in cancer (9).In contrast, SHIP dephosphorylates the 5′ position on the inositol ring and produces phosphatidylinositol 3,4-bisphosphate (10). There are three isoforms of SHIP: the 145-kDa hematopoietic cell restricted SHIP (also known as SHIP1); the 104-kDa stem cell-restricted SHIP, sSHIP; and the more widely expressed 150-kDa SHIP2 (11). SHIP1 is the major inositol phosphatase regulating PtdIns 3,4,5-P₃ in monocytes, macrophages, B cells, and T cells (11). SHIP1 has three known structural features: the N-terminal SH2 domain, the central inositol 5′ phosphatase domain, and two NPXY sequences in the C-terminal region. The currently accepted model for regulation of PtdIns 3,4,5-P₃ levels by SHIP1 envisions translocation of SHIP1 from the cytosol to the membrane. Upon stimulation by growth factors, cytokine receptors, or immunoreceptors, SHIP1 is recruited via its N-terminal SH2 domain to phosphorylated tyrosine residues in receptor kinases and degrades the elevated levels of PtdIns 3,4,5-P₃ near the activated receptor (12). During this translocation process, SHIP1 is not thought to change its 5′ phosphatase activity (13). Although it is known that SHIP1 can be phosphorylated on tyrosine residues by the lyn cytoplasmic kinase (12) or following the activation of the T cell receptor (14), neither event appears to influence the 5′ phosphatase activity. To date, direct regulation of SHIP1 activity by serine/threonine kinases has not been studied.Activation of G protein-coupled receptors that raise cAMP (i.e. β-adrenergic receptors or adenosine A_2a receptors) is known to blunt the pro-inflammatory responses generated by receptors that raise the level of PtdIns 3,4,5-P₃ (15). Therefore, we investigated the possibility that phosphorylation of SHIP1 by cyclic AMP-dependent protein kinase (PKA) might regulate the activity of SHIP1. We found that SHIP1 can be phosphorylated by PKA both in vitro and in cells leading to a stimulation of SHIP1 activity. Activation of PKA in DT40 and A20 cells blunted indicators of the PtdIns 3,4,5-P₃ response to B cell receptor stimulation. These results indicate that SHIP1 activity can be regulated both in vitro and in cells by activation of the cyclic AMP-dependent protein kinase and highlight a new mode of SHIP regulation by G protein-coupled receptors.     

Chikungunya: A Potentially Emerging Epidemic?

Chikungunya virus is a mosquito-borne emerging pathogen that has a major health impact in humans and causes fever disease, headache, rash, nausea, vomiting, myalgia, and arthralgia. Indigenous to tropical Africa, recent large outbreaks have been reported in parts of South East Asia and several of its neighboring islands in 2005–07 and in Europe in 2007. Furthermore, positive cases have been confirmed in the United States in travelers returning from known outbreak areas. Currently, there is no vaccine or antiviral treatment. With the threat of an emerging global pandemic, the peculiar problems associated with the more immediate and seasonal epidemics warrant the development of an effective vaccine. In this review, we summarize the evidence supporting these concepts.     

Novel semicarbazones based 2,5-disubstituted-1,3,4-oxadiazoles: One more step towards establishing four binding site pharmacophoric model hypothesis for anticonvulsant activity

A series of novel N¹-{5-[(naphthalene-2-yloxy)methyl]-1,3,4-oxadiazol-2-yl}-N⁴-(4-substitutedbenzaldehyde)-semicarbazone, N¹-{5-[(naphthalene-2-yloxy)methyl]-1,3,4-oxadiazol-2-yl}-N⁴-[1-(4-substitutedphenyl)ethanone]-semicarbazone and N¹-{5-[(naphthalene-2-yloxy)methyl]-1,3,4-oxadiazol-2-yl}-N⁴-[1-(4-substitutedphenyl) (phenyl) methanone]-semicarbazone were designed and synthesized on the basis of semicarbazone based pharmacophoric model to meet the structural requirements necessary for anticonvulsant activity. The anticonvulsant activities of the compounds were investigated using maximal electroshock seizure (MES), subcutaneous pentylenetrtrazole (scPTZ) and subcutaneous strychnine (scSTY) models. Some of the selected active compounds were subjected to GABA assay to confirm their mode of action. The efforts were also made to establish structure activity relationships among synthesized compounds. The results of the present studying validated that the pharmacophoric model with four binding sites is essential for anticonvulsant activity.