Will climate change affect outbreak patterns of planthoppers in Bangladesh?

Recently, planthoppers outbreaks have intensified across Asia resulting in heavy rice yield losses. The problem has been widely reported as being induced by insecticides while other factors such as global warming that could be potential drivers have been neglected. Here, we speculate that global warming may increase outbreak risk of brown planthopper (Nilaparvata lugens Stål.). We present data that demonstrate the relationship between climate variables (air temperature and precipitation) and the abundance of brown planthopper (BPH) during 1998-2007. Data show that BPH has become significantly more abundant in April over the 10-year period, but our data do not indicate that this is due to a change in climate, as no significant time trends in temperature and precipitation could be demonstrated. The abundance of BPH varied considerably between months within a year which is attributed to seasonal factors, including the availability of suitable host plants. On the other hand, the variation within months is attributed to fluctuations in monthly temperature and precipitation among years. The effects of these weather variables on BPH abundance were analyzed statistically by a general linear model. The statistical model shows that the expected effect of increasing temperatures is ambiguous and interacts with the amount of rainfall. According to the model, months or areas characterized by a climate that is either cold and dry or hot and wet are likely to experience higher levels of BPH due to climate change, whereas other combinations of temperature and rainfall may reduce the abundance of BPH. The analysis indicates that global warming may have contributed to the recent outbreaks of BPH in some rice growing areas of Asia, and that the severity of such outbreaks is likely to increase if climate change exaggerates. Our study highlights the need to consider climate change when designing strategies to manage planthoppers outbreaks.

Central cholinergic activation of a vagus nerve-to-spleen circuit alleviates experimental colitis.

The cholinergic anti-inflammatory pathway is an efferent vagus nerve-based mechanism that regulates immune responses and cytokine production through α7 nicotinic acetylcholine receptor (α7nAChR) signaling. Decreased efferent vagus nerve activity is observed in inflammatory bowel disease. We determined whether central activation of this pathway alters inflammation in mice with colitis and the mediating role of a vagus nerve-to-spleen circuit and α7nAChR signaling. Two experimental models of colitis were used in C57BL/6 mice. Central cholinergic activation induced by the acetylcholinesterase inhibitor galantamine or a muscarinic acetylcholine receptor agonist treatments resulted in reduced mucosal inflammation associated with decreased major histocompatibility complex II level and pro-inflammatory cytokine secretion by splenic CD11c⁺ cells mediated by α7nAChR signaling. The cholinergic anti-inflammatory efficacy was abolished in mice with vagotomy, splenic neurectomy, or splenectomy. In conclusion, central cholinergic activation of a vagus nerve-to-spleen circuit controls intestinal inflammation and this regulation can be explored to develop novel therapeutic strategies.

Trichogramma zahiri (Hymenoptera: Trichogrammatidae) an egg parasitoid of the rice hispa Dicladispa armigera (Coleoptera: Chrysomelidae) in Bangladesh.

Trichogramma zahiri Polaszek sp. n. is described from Bangladesh. It has been collected at several localities from the major pest of rice Dicladispa armigera (Olivier) on which it has an important controlling impact. Trichogramma zahiri is compared with known Trichogramma species from the region, and diagnostic differences are presented. Data on developmental period, adult longevity, egg-laying frequency, host egg age preference and seasonal parasitism rate are presented and discussed. Other records of parasitoids of D. armigera are briefly reviewed and discussed.

Mycobacterium avium complex activates nuclear factor kappaB via induction of inflammatory cytokines.

A variety of microorganisms has been reported to directly induce NF-kappaB, a critical step in the regulation of genes involved in the cellular immune response. In this study, we demonstrate that proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha) produced upon activation by the Mycobacterium avium complex (MAC) preceed NF-kappaB activity in U937, a human monocytoid cell line. MAC induction of TNFalpha mRNA expression was detected within 15 min after MAC infection, whereas enhanced NF-kappaB binding activity was not detected until 90 to 120 min postinfection. Supershift analysis revealed increased p50 in the MAC-induced NF-kappaB binding complexes. Consistent with an autocrine mechanism, anti-TNFalpha antibody and dexamethasone, a known cytokine inhibitor, both completely suppressed the effect of MAC on the induction of NF-kappaB. Taken together, these findings suggest that exposure of monocyte cell membranes to MAC induces endogenous TNFalpha, which in turn enhances NF-kappaB binding activity. The rapid induction of TNFalpha may be important in the initial host response to MAC infection.

Interleukin-10 enhances tumor necrosis factor-alpha activation of HIV-1 transcription in latently infected T cells.

Interleukin-10 (IL-10) is elevated in HIV-1-infected individuals and has been implicated in disease progression. We previously reported that IL-10 cooperates with tumor necrosis factor-alpha (TNF-alpha) to activate HIV-1 expression synergistically in acutely infected monocyte-derived macrophages and the chronically infected U1 promonocytic cell line. To determine whether IL-10 also cooperates with TNF-alpha to activate latent HIV-I expression in lymphocytes, we examined the effects of IL-10 on proviral expression in the chronically infected T-cell line, ACH-2. Although IL-10 inhibited HIV-1 expression acting alone, in combination with suboptimal concentrations of TNF-alpha, IL-10 increased HIV-1 steady-state mRNA expression and p24 core antigen production in ACH-2 cells. Interestingly, IL-10 concentrations that synergistically induced virus also maximally stimulated endogenous TNF-alpha expression, suggesting that cell-derived TNF-alpha may contribute to cytokine synergy. Transfection studies in ACH-2 cells indicated that IL-10 combined with TNF-alpha to activate the HIV-1 long terminal repeat (LTR). IL-10 also cooperated with TNF-alpha to activate HIV-1 LTR in 1G5 cells, a Jurkat T-cell line stably transfected with an LTR-dependent luciferase reporter gene. Pyrrolidine dithiocarbamate, a potent transcriptional inhibitor of the viral LTR, abrogated the cytokine responses in both U1 and ACH-2 cells, suggesting a common TNF-alpha-mediated transcriptional mechanism in these cell types despite their different modes of provirus latency. Taken collectively, these data suggest that IL-10 enhances suboptimal TNF-alpha activation of HIV-1 transcription in chronically infected T-cells at least in part through induction of endogenous TNF-alpha expression.

The cAMP-dependent protein kinase A and protein kinase C-beta pathways synergistically interact to activate HIV-1 transcription in latently infected cells of monocyte/macrophage lineage.

The HIV-1 long terminal repeat (LTR) responds to a variety of cellular signal transduction pathways. We demonstrate that the cAMP-dependent protein kinase A (PKA) and protein kinase C (PKC) signaling pathways synergize to increase HIV-1 LTR-mediated transcription and viral replication in a latently infected promonocytic cell line (U1). The LTR-mediated synergy induced by cholera toxin (Ctx), a potent activator of the cAMP-dependent PKA pathway, and the PKC activator phorbol 12-myristate 13-acetate (PMA) was abrogated by a PKC-beta-specific inhibitor (LY333531). In contrast, the LTR-mediated synergy induced by Ctx and TNF alpha was not affected by LY333531. The synergy induced by Ctx and TNF alpha was also abrogated by mutation of the cAMP-responsive downstream sequence elements (DSE) in the 5' untranslated leader region, whereas the DSE mutations did not affect the synergy induced by Ctx and PMA. These distinctions indicate that Ctx cooperates differently with TNF alpha and PMA to activate the HIV-1 LTR. Ctx and PMA synergistically activated AP-1- and NF-kappa B-dependent transcription, even though no cooperative binding of AP-1 or NF-kappa B was observed in gel shift assays. An extensive mutational analysis of the HIV-1 LTR that included the NF-kappa B and AP-1 binding sites revealed no distinct cis-acting element or region within the HIV-1 LTR that was required for the transcriptional synergy. Ctx and PMA also synergistically interact to activate the HTLV-1 LTR. These results indicate that the transcriptional synergy elicited by Ctx and PMA targets multiple functional elements and promoters, requires a cooperative interaction between the PKA and PKC-beta pathways, and differs mechanistically from the transcriptional synergy induced by Ctx and TNF alpha.

TNFalpha cooperates with the protein kinase A pathway to synergistically increase HIV-1 LTR transcription via downstream TRE-like cAMP response elements.

Activating protein-1 (AP-1) binding TPA responsive elements (TRE) are located downstream of the transcription initiation site in the U5 region of the HIV-1 long terminal repeat (LTR). These downstream sequence elements, termed DSE, can bind both AP-1 and CREB/ATF transcription factors. Recently, we demonstrated that the DSE are also cAMP-responsive elements (CRE), since they mediated activation signals elicited by cholera toxin (Ctx), a potent activator of the cAMP-dependent protein kinase A (PKA) signal transduction pathway. In the present study, we demonstrate that the HIV-1 DSE can mediate the transcriptional synergy elicited by the combination of Ctx and TNFalpha. Ctx combined with TNFalpha or IL-1beta to produce a synergistic increase in p24 antigen production in U1 promonocytic cells. Transfection studies of LTR reporter constructs indicated that mutation of the DSE sites abrogated the LTR-mediated synergy induced by Ctx and TNFalpha, whereas the synergy induced by Ctx and IL-1beta was unaffected, suggesting TNFalpha and IL-1beta cooperate differently with the cAMP/PKA activation pathway to induce HIV-1 expression in U1 cells. Because the DSE are also TRE sites, we assessed the effect of the agonist combinations on AP-1-dependent transcription. TNFalpha as well as IL-1beta cooperated with Ctx to produce a synergistic activation of AP-1-mediated transcription. These data indicate that the TRE-like cAMP-responsive DSE sites within the 5'-untranslated leader can mediate the transcriptional cooperativity between TNFalpha and the cAMP/PKA pathway. Since the DSE and TRE sites cannot bind CREB/ATF homodimers, we propose a mechanism in which the HIV-1 DSE bind heterodimers composed of both AP-1 and CREB/ATF proteins.

Interleukin-10 inhibits interferon-gamma-induced intercellular adhesion molecule-1 gene transcription in human monocytes.

Interleukin-10 (IL-10) is a potent monocyte regulatory cytokine that inhibits gene expression of proinflammatory mediators. In this study, we investigated the mechanism by which IL-10 downregulates expression of intercellular adhesion molecule-1 (ICAM-1) on the cell surface of normal human monocytes activated with interferon-gamma (IFN-gamma). IL-10 inhibition of IFN-gamma-induced ICAM-1 expression was apparent as early as 3 hours and was blocked by an anti-IL-10 antibody but not by an isotype-matched control antibody. Northern blot analysis showed that IL-10 reduced the accumulation of ICAM-1 mRNA in IFN-gamma-stimulated monocytes. IL-10 inhibition of ICAM-1 steady-state mRNA was detected at 3 hours and remained at 24 hours. Nuclear run-on transcription assays showed that IL-10 inhibited the rate of IFN-gamma-induced transcription of the ICAM-1 gene, and mRNA stability studies showed that IL-10 did not alter the half-life of IFN-gamma-induced ICAM-1 message. Thus, IL-10 inhibits IFN-gamma-induced ICAM-1 expression in monocytes primarily at the level of gene transcription. Activation of IFN-gamma-responsive genes requires tyrosine phosphorylation of the transcriptional factor STAT-1alpha (signal transducer and activator of transcription-1alpha). However, IL-10 did not affect IFN-gamma-induced tyrosine phosphorylation of STAT-1alpha or alter STAT-1alpha binding to the IFN-gamma response element (IRE) in the ICAM-1 promoter. Instead, IL-10 prevented IFN-gamma-induced binding activity at the NF-kappaB site of the tumor necrosis factor alpha (TNF-alpha)-responsive NF-kappaB/C-EBP composite element in the ICAM-1 promoter. These data indicate that IL-10 inhibits IFN-gamma-induced transcription of the ICAM-1 gene by a regulatory mechanism that may involve NF-kappaB.

U5 region of the human immunodeficiency virus type 1 long terminal repeat contains TRE-like cAMP-responsive elements that bind both AP-1 and CREB/ATF proteins.

Activating protein-1 (AP-1) binding phorbol ester responsive elements (TRE) are located downstream of the transcription initiation site in the U5 region of the human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR). These downstream sequence elements, termed DSE, can bind cFos and junD and transmit protein kinase C (PKC) activation signals to the LTR. Further studies suggested the DSE might also bind AP-1-related proteins of the CREB/ATF family. Since enhanced HIV-1 expression is associated with activation of the cAMP-dependent protein kinase A (PKA) signaling pathway, we determined whether binding of CREB/ATF proteins to the DSE mediate cAMP/PKA activation of the HIV-1 LTR. In the present study. DSE binding complexes in nuclear protein extracta from colonic epithelial cells are shown to contain ATF-1, ATF-2, and CREB and transfection of either an ATF-2 or PKA expressing plasmid transactivated the DSE. Cholera toxin (Ctx), a potent activator of the cAMP/PKA pathway. Increased HIV-1 virus production from a latently infected promonocytic cell line, U1. Ctx increased LTR promoter activity and increased the CREB content of DSE binding complexes. Transfection of U1 cells with a series of mutant LTR reporter constructs demonstrated that the Ctx response was in large part mediated by the DSE. The Ctx response was also mediated by a heterologous promoter containing multiple TRE sites. Nuclear protein extracts from a T-cell line infected by HIV-1 contained higher levels of CREB/ATF proteins and manifested increased CREB/ATF binding activity. Collectively, these results indicate the DSE are TRE-like cAMP responsive elements that bind both AP-1 and CREB/ATF permitting induction of the HIV-1 LTR by both PKC and PKA activation signals.

HIV-1 Tat protein can transactivate a heterologous TATAA element independent of viral promoter sequences and the trans-activation response element.

OBJECTIVE: To determine whether the HIV-1 transactivator protein Tat acts as a DNA sequence-specific transcription factor and activates transcription from a heterologous TATAA element in the absence of the trans-activation response (TAR) element and other sequences in the HIV-1 long terminal repeat (LTR). DESIGN: Activating protein-1 (AP-1) and Tat-induced transcription were assessed using Jun and hybrid Tat/Jun-expression plasmids and reporter gene constructs which contained AP-1 binding sites upstream of the rat prolactin TATAA element or an HIV-1 LTR construct in which AP-1 binding sites replaced the TAR element. METHODS: Tat-induced transcription was determined following transient transfection of colon epithelial cell lines with reporter gene constructs and Tat/Jun-expression plasmids in which Tat was fused to the DNA binding domain of Jun. Activation of prolactin (PL) and LTR reporter genes was assessed by luciferase (LUC) or chloramphenicol acetyltransferase (CAT) activity in cellular extracts. RESULTS: Cotransfection of cells with Tat/Jun and the AP-1 PL LUC or LTR AP-1 CAT reporter plasmid resulted in a marked increase in reporter gene activity which was comparable with that induced by transfection of cells with several different AP-1 expression plasmids (e.g., JunD, JunB, c-Fos), or that elicited by stimulation of the cells transfected with LTR AP-1 CAT plasmids with phorbol ester or tumor necrosis factor-alpha. Tat-induced transcription was DNA-mediated since both a Jun DNA binding domain fused to Tat as well as AP-1 binding sites within the promoter were required for the induction of CAT expression. CONCLUSIONS: Tat-activated transcriptor can occur strictly through a heterologous TATAA element independent of TAR and Sp1 binding sites or other HIV-1 LTR sequences. Tat appears to increase transcription initiated through the TATAA element by mechanisms similar to that of DNA sequence-specific transcription factors.