S63845 The p MAPK pathway activates AP to regulate

The p38 MAPK pathway activates AP1 to regulate transcription of TNF-α [32,33]. Our results show that EC inhibits the expression of total c-Jun and p-c-Jun in the lungs of LPS-challenged mice. This finding suggests that EC may inhibit TNF-α production in the lungs via the p38 MAPK–AP1 signaling pathway.
Introduction Plants have to face the threats of invasion from numerous types of stresses, including animal, herbivorous, and pathogen attacks. Herbivorous insects and pathogens not only cause mechanical tissue damages, but also affect the growth and reproduction of plants. Thus, plants develop complex defense systems, which enable them resist threats effectively. Because defense is costly, plants develop inducible mechanisms to activate or amplify the response to stresses. Under pathogen and herbivorous attacks, plants produce various defence-related hormones, including ethylene (ET), methyl jasmonate (MJ), salicylic acid, and peptide-hormones [1,2], to unlock the defence-related regulatory networks [3]. After defence-related regulatory networks are unlocked, multifarious molecules, including nitric oxide, cytosolic calcium (Ca2+), and reactive oxygen species [1,4,5], are induced by plants to activate defense-related and anti-microbial genes [6]. The defense-related proteins, including Arabidopsis defensin PDF1.2 [3], pathogenesis-related proteins PR [7], tomato proteinase inhibitors PI [8,9], and tobacco endochitinase [10], are used against pathogen attacks. The sweet potato carbohydrate-binding proteins Ipomoelin (IPO) [11] and Phenylalanine ammonia lyase (PAL) [12,13] can interfere with the growth of herbivorous insects and modulate secondary metabolites, respectively. Wounding created by mechanical damages or herbivore attacks influences the growth and reproduction of plants. Plants activate wound responses through the transduction of extracellular stimuli into plant S63845 [14,15]. Mitogen-activated protein kinases (MAPKs) are the intracellular signal transducers that transduce extracellular stimuli into plant cells through three layers of protein kinases, which are MAPK kinase kinases (MAPKKKs), MAPK kinases (MAPKKs), and MAPKs [16]. In response to stimulants, MAPKKKs phosphorylate and thus activate MAPKKs, which in turn phosphorylate MAPKs. Phosphorylated MAPKs translocate from the cytoplasm into the nucleus, and regulates gene expression [17]. In plants, MAPKs play essential roles mediating responses to various stress stimuli [18,19]. MAPKs are reportedly activated during wounding in plants. In Nicotiana attenuata, two MAPKs, wounding-induced protein kinase (NaWIPK) and salicylic acid-induced protein kinase (NaSIPK), are rapidly activated in response to wounding [20]. The overexpression of NaSIPK in tobacco increases the JA level and activates protease inhibitors [17,21]. In Lolium temulentum, p44 and p46 MAPKs are rapidly activated by wounding and are associated with long distance signal transduction [22]. In sweet potato, wounding induces the IbMEK1/IbMAPK cascade, which activates the expression of IPO [23,24]. In addition, tomato when treated with systemin, a peptide hormone that activates JA biosynthesis, shows rapid activation of tomato MAPK [25]. These findings suggest that MAPK pathways act as signal transducers that mediate the defense responses of plants upon wounding. P38 MAPK is a highly conserved serine-threonine protein kinase that plays an important role in response to environmental stresses [26,27]. It acts as a stress-activated protein kinase (SAPK) in a diverse range of eukaryotic organisms from yeasts to mammals [[28], [29], [30], [31]]. Studies of p38 MAPK are usually performed using highly specific antibodies against the phosphorylated p38 MAPK [32]. In the algae Dunaliella viridis, the amount of pp38-like MAPK is elevated to adapt to hyperosmotic, thermal, and UV stresses [33,34]. In wheat, pp38-like MAPK directs the reorganization of cytoskeleton under hyperosmotic stress [35]. In addition, the stress responsive roles of p38 MAPK are also reported in Vicia faba L [[36], [37], [38]] and tobacco [39]. Although the function of p38 MAPK is known as a stress response MAPK in yeast, flies, and animals, it has not been well studied in plants.