Protection against rotavirus diarrhoea in mice by trypsin inhibitor

To investigate the role of soyabean trypsin inhibitor (TI) during rotavirus (RV) diarrhoea, changes in enzyme activities of six relevant mucosal enzymes (lactase, sucrase, maltase, trehalase, glucoamylase and alkaline phosphatase) were assayed following inoculation of suckling mice with EB rotavirus (serotype 3) along with the TI and compared with the age-matched healthy control mice. The animals were divided into three groups i.e. group 1 (controls), group 2 (RV inoculated) and group 3 (RV + TI inoculated and sacrificed under light anaesthesia on 0, 1, 3, 5, 7 and 10 day post inoculation (dpi). Then intestines were excised and divided into two parts (jejunum and ileum). They were separately homogenized in 0.9% cold normal saline and activities of mucosal enzyme were measured. Alkaline phosphatase and disaccharidases were found to be decreased significantly in RV inoculated animals in both the anatomical portions of small intestine of mice. These enzyme levels were restored with the administration of TI i.e. in group 3 and became comparable to the controls in both intestinal portions. These studies suggest that activity of intestinal enzymes which are important in digestive absorptive functions of small intestine were restored with the addition of TI whengiven to infant mice showing its protective efficacy during rotavirus infection.     

Interaction of hematopoietic progenitor kinase 1 and c-Abl tyrosine kinase in response to genotoxic stress

The c-Abl protein tyrosine kinase is activated by certain DNA-damaging agents and regulates induction of the stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). The hematopoietic progenitor kinase 1 (HPK1) has also been shown to act upstream to the SAPK/JNK signaling pathway. We report here that exposure of hematopoietic Jurkat T cells to genotoxic agents is associated with activation of HPK1. The results demonstrate that exposure of Jurkat cells to DNA-damaging agents is associated with translocation of active c-Abl from nuclei to cytoplasm and binding of c-Abl to HPK1. Our findings also demonstrate that c-Abl phosphorylates HPK1 in cytoplasm and stimulates HPK1 activity. The functional significance of the c-Abl-HPK1 interaction is supported by the demonstration that this complex regulates SAPK/JNK activation. Overexpression of c-Abl(K-R) inhibits HPK1-induced activation of SAPK/JNK. Conversely, the dominant negative mutant of HPK1 blocks c-Abl-mediated induction of SAPK/JNK. These findings indicate that activation of HPK1 and formation of HPK1/c-Abl complexes are functionally important in the stress response of hematopoietic cells to genotoxic agents.     

Eicosanoids mediate nodulation reactions to bacterial infections in adults of two 17-year periodical cicadas,Magicicada septendecim and M. cassini

Nodulation is the first and quantitatively most important cellular defense reaction to bacterial infections in insects. Treating adults of the 17-year periodical cicadas, Magicicada septendecim and M. cassini, with eicosanoid biosynthesis inhibitors immediately prior to intrahemocoelic injections of the bacterium, Serratia marcescens, sharply reduced the nodulation response to bacterial challenges. Separate treatments with specific inhibitors of phospholipase A(2), cyclooxygenase, and lipoxygenase reduced nodulation, supporting our view that nodule formation is a multi-step process in which individual steps are separately mediated by lipoxygenase and cyclooxygenase products. The inhibitory influence of dexamethasone was apparent by 2 h after injection, and nodulation was significantly reduced, relative to control insects, over the following 14 h. The dexamethasone effects were reversed by treating bacteria-challenged insects with the eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. Low levels of arachidonic acid were detected in fat body phospholipids. These findings in adults of an exopterygote insect species with an unusual life history pattern broaden our hypothesis that eicosanoids mediate cellular immune reactions to bacterial infections in most, if not all, insects.     

Eicosanoids mediate nodulation reactions to bacterial infections in adults of the cricket,Gryllus assimilis

Nodulation is the temporally and quantitatively most important cellular defense reaction to bacterial infections in insects. Inhibition of eicosanoid biosynthesis in adults of the cricket, Gryllus assimilis, immediately prior to intrahemocoelic injections of the bacterium, Serratia marcescens, sharply reduced the nodulation response. Separate treatments with specific inhibitors of phospholipase A(2), cyclooxygenase, and lipoxygenase reduced nodulation, supporting our view that nodule formation is a complex process involving lipoxygenase and cyclooxygenase products. The inhibitory influence of dexamethasone was apparent within 2h of injection, and nodulation was significantly reduced, relative to control crickets, over 22h. The dexamethasone effects were reversed by treating bacteria-injected insects with the eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. Low levels of arachidonic acid were detected in fat body phospholipids, and fat body preparations were shown to be competent to biosynthesize eicosanoids from exogenous radioactive arachidonic acid. These findings in a hemimetabolous insect broaden our hypothesis that eicosanoids mediate cellular immune reactions to bacterial infections in most, if not all, insects.     

Androgen regulates follicle-stimulating hormone beta gene expression in an activin-dependent manner in immortalized gonadotropes

Little is known about the molecular mechanisms of androgen regulation of the FSHbeta gene; however, studies suggest that it consists of a complex feedback loop that involves multiple mechanisms acting at both the level of the hypothalamus and the pituitary. In the present study, we address androgen regulation of the FSHbeta gene in immortalized gonadotrope cells and investigate the roles of activin and GnRH in androgen action. Using transient transfection assays in the FSHbeta-expressing mouse gonadotrope cell line, LbetaT2, we demonstrate that androgens stimulate expression of an ovine FSHbeta reporter gene in a dose-dependent manner. Mutation of either of two conserved androgen response elements at -245/-231 and -153/-139 within the proximal region of the ovine FSHbeta gene promoter abolishes this stimulation, and androgen receptor binds directly to the -244 ARE in vitro. Androgen induction of the FSHbeta reporter gene is also dependent upon the activin autocrine loop present in the LbetaT2 cells, as well as an activin-response element at -138/-124 of the FSHbeta gene. However, activin regulation of other genes remains unaffected by androgens. In addition, androgens stimulate expression of a mouse GnRH receptor reporter gene, and thus may indirectly augment the response of the FSHbeta gene to GnRH. Taken together, these data demonstrate that, in mouse gonadotropes, androgens act directly on the ovine FSHbeta gene to stimulate expression by a mechanism that is dependent upon activin, as well as acting indirectly, potentially through a second mechanism that may be dependent upon induction of GnRH receptor.     

Resistance to oxidative stress in a freshwater fish Channa punctatus after exposure to inorganic arsenic

The biochemical toxicity of arsenic trioxide (As^III) in a freshwater edible fish Channa punctatus has been studied on exposures ranging from 7 to 90 d. The arsenic concentration increased exponentially in liver, kidney, gills, and muscles of fish up to 60 d of exposure to arsenic. However, arsenic concentration in these tissues declined at 90 d of exposure. This relationship between period of exposure and concentration of arsenic in selected tissues suggests an adaptive response of fish to arsenic. Furthermore, exposure to arsenic-induced lipid peroxidation in these organs increased initially at 7 d of exposure; however, it decreased up to 60 d of exposure but increased again at 90 d of treatment. Values of reduced glutathione (GSH) reflected the observations of lipid peroxidation. The role of GSH in this adaptive response has been discussed.     

Modulating HIV-1 replication by RNA interference directed against human transcription elongation factor SPT5

Background

Dendritic cell (DC) transmission of human immunodeficiency virus (HIV) to CD4+ T cells occurs across a point of cell-cell contact referred to as the infectious synapse. The relationship between the infectious synapse and the classically defined immunological synapse is not currently understood. We have recently demonstrated that human B cells expressing exogenous DC-SIGN, DC-specific intercellular adhesion molecule-3 (ICAM-3)-grabbing nonintegrin, efficiently transmit captured HIV type 1 (HIV-1) to CD4+ T cells. K562, another human cell line of hematopoietic origin that has been extensively used in functional analyses of DC-SIGN and related molecules, lacks the principal molecules involved in the formation of immunological synaptic junctions, namely major histocompatibility complex (MHC) class II molecules and leukocyte function-associated antigen-1 (LFA-1). We thus examined whether K562 erythroleukemic cells could recapitulate efficient DC-SIGN-mediated HIV-1 transmission (DMHT).

Results

Here we demonstrate that DMHT requires cell-cell contact. Despite similar expression of functional DC-SIGN, K562/DC-SIGN cells were inefficient in the transmission of HIV-1 to CD4+ T cells when compared with Raji/DC-SIGN cells. Expression of MHC class II molecules or LFA-1 on K562/DC-SIGN cells was insufficient to rescue HIV-1 transmission efficiency. Strikingly, we observed that co-culture of K562 cells with Raji/DC-SIGN cells impaired DMHT to CD4+ T cells. The K562 cell inhibition of transmission was not directly exerted on the CD4+ T cell targets and required contact between K562 and Raji/DC-SIGN cells.

Conclusions

DMHT is cell type dependent and requires cell-cell contact. We also find that the cellular milieu can negatively regulate DC-SIGN transmission of HIV-1 in trans.