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The involvement of calcium and calcium-activated calmodulin (Ca 2ϩ -CaM) in heat shock (HS) signal transduction in wheat (Triticum aestivum) was investigated. Using Fluo-3/acetoxymethyl esters and laser scanning confocal microscopy, it was found that the increase of intracellular free calcium ion concentration started within 1 min after a 37°C HS. The levels of CaM mRNA and protein increased during HS at 37°C in the presence of Ca 2ϩ . The expression of hsp26 and hsp70 genes was up-regulated by the addition of CaCl 2 and down-regulated by the calcium ion chelator EGTA, the calcium ion channel blockers LaCl 3 and verapamil, or the CaM antagonists N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and chlorpromazine. Treatment with Ca 2ϩ also increased, and with EGTA, verapamil, chlorpromazine, or trifluoperazine decreased, synthesis of HS proteins. The temporal expression of the CaM1-2 gene and the hsp26 and hsp70 genes demonstrated that up-regulation of the CaM1-2 gene occurred at 10 min after HS at 37°C, whereas that of hsp26 and hsp70 appeared at 20 min after HS. A 5-min HS induced expression of hsp26 after a period of recovery at 22°C after HS at 37°C. Taken together, these results indicate that Ca 2ϩ -CaM is directly involved in the HS signal transduction pathway. A working hypothesis about the relationship between upstream and downstream of HS signal transduction is presented.Organisms have developed a diverse array of mechanisms for adapting to environmental changes. One of the best characterized responses is the induction of heat shock proteins (HSPs). The heat shock (HS) response has been found in almost every organism studied to date. The HSPs are synthesized by cells in response to elevated temperature but are also induced by other environmental stresses (Noven et al., 1992; Kilstrup et al., 1997) and play an important role in the thermotolerance of plants (Queitsch et al., 2000; Burke, 2001). A connection between HS response and oxidative stress has been observed (Gong et al., 1997a;Lee et al., 2000;Larkindale and Knight, 2002; Panchuk et al., 2002). The HSPs are divided into several families based on their molecular mass, and most have molecular chaperones functions (for review, see Boston et al., 1996;Miernyk, 1999). Angiosperms synthesize more small HSPs (smHSPs) than other organisms. These smHSPs are likely critical for survival of heat stress and for specific developmental processes in plants (Waters et al., 1996).The changes in cytoplasmic calcium levels act as a ubiquitous signal in eukaryotic cells. HS induced a large increase in intracellular free calcium ion concentration ([Ca 2ϩ ] i ) in Chinese hamster (Cricetulus barabensis) HA-1 fibroblasts (Calderwood et al., 1988). In plants, Gong et al. (1998) observed that HS caused a transient increase in [Ca 2ϩ ] i . The change in [Ca 2ϩ ] i is also involved in regulating the binding activity of the HS transcription factor (HSF) to the HS element (Mosser et al., 1990), the synthesis of HSPs (Kiang et al., 1994;Kuznetsov et al., 1998), and...

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SUMMARYAn increased concentration of cytosolic calcium ions (Ca 2+ ) is an early response by plant cells to heat shock.However, the molecular mechanism underlying the heat-induced initial Ca 2+ response in plants is unclear. In this study, we identified and characterized a heat-activated Ca 2+-permeable channel in the plasma membrane of Arabidopsis thaliana root protoplasts using reverse genetic analysis and the whole-cell patch-clamp technique. The results indicated that A. thaliana cyclic nucleotide-gated ion channel 6 (CNGC6) mediates heatinduced Ca 2+ influx and facilitates expression of heat shock protein (HSP) genes and the acquisition of thermotolerance. GUS and GFP reporter assays showed that CNGC6 expression is ubiquitous in A. thaliana, and the protein is localized to the plasma membrane of cells. Furthermore, it was found that the level of cytosolic cAMP was increased by a mild heat shock, that CNGC6 was activated by cytosolic cAMP, and that exogenous cAMP promoted the expression of HSP genes. The results reveal the role of cAMP in transduction of heat shock signals in plants. The correlation of an increased level of cytosolic cAMP in a heat-shocked plant with activation of the Ca 2+ channels and downstream expression of HSP genes sheds some light on how plants transduce a heat stimulus into a signal cascade that leads to a heat shock response.

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Psoriasis is characterized by resistance to infections, which is regulated by antimicrobial proteins. Whether antimicrobial proteins play a pathogenic role in psoriasis remains unclear. In this study, we aimed to elucidate the role of lipocalin-2 (Lcn2), an antimicrobial protein, in the pathogenesis of psoriasis. Our results showed that Lcn2 was highly expressed in the lesional skin of psoriatic patients. The neutralization of Lcn2 alleviated epidermal hyperplasia, inflammation, and especially neutrophil infiltration in an imiquimod-induced psoriasis-like murine model. In vitro, Lcn2 stimulated human neutrophils to produce vital proinflammatory mediators, such as IL-6, IL-8, tumor necrosis factor-α, and IL-1α via a specific receptor, 24p3R, on neutrophils, which consequently activated the downstream extracellular signal-regulated kinase-1/2 and p38-mitogen-activated protein kinase signaling pathways. Moreover, Lcn2-induced neutrophil chemotaxis was concentration dependent and mediated by the extracellular signal-regulated kinase-1/2 and p38-mitogen-activated protein kinase signaling pathways in vitro. Furthermore, we demonstrated that both keratinocytes and neutrophils were the sources of Lcn2 in the lesional skin of psoriatic patients. Taken together, these results suggest that Lcn2 is involved in the pathogenesis of psoriasis by modulating neutrophil function, and that it could serve as a potential target for treating psoriasis.

BackgroundWe report the concentrations and distributions of urinary arsenic (As) metabolites in 233 residents exposed to 20, 90, or 160 μg/L inorganic arsenic (iAs) in drinking water from three villages in Hohhot, Inner Mongolia, China, that formed one control and two exposed groups.MethodsWe used hydride generation-atomic absorption spectrometry (HGAAS) to determine iAs, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA).ResultsThe concentrations of each urinary As species in the two exposed groups were significantly higher than in the control group for both children and adults. Both children and adults in exposed groups had higher percent iAs and MMA and lower percent DMA, and low primary and secondary methylation indices (PMI and SMI, respectively) than those in the control group. However, children showed significant increases in percent DMA and the SMI as well as decreases in the percent MMA when the iAs exposure level increased from 90 to 160 μg/L. In addition, children in the two exposed groups showed lower percent MMA but higher percent DMA and higher SMI than adults in the same exposed group. No significant differences in As metabolite concentrations and distributions were found between males and females in each group. A significant correlation was also found in the SMI between 11 pairs of children and their mothers from the 160-μg/L–exposed group.ConclusionsChildren had higher a capacity for secondary methylation of As than adults when exposed to the same concentrations of iAs in drinking water. Exposure to As may increase the capacity for methylation in children to some extent.

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