p38 MAPK as a signal transduction component of heavy metals stress in Euglena gracilis

Abstract

Living organisms are subject to stress, and among these stressors, heavy metals exposure triggers accumulation of sulfur metabolites. Among these metabolites, glutathione and phytochelatins are found in several organisms, such as Euglena gracilis. Pre-exposing E. gracilis to low concentrations of Hg2+ generates a population with resistance to even 0.2 mM Cd2+, and this resistance relies partly on phytochelatins. p38 MAPK is stimulated by stress and is involved in apoptotic as well as survival mechanisms. In this study, we explored its participation in heavy metal-induced stress and its possible role in sulfur metabolite accumulation. We found that about 51% of the E. gracilis pretreated with Hg2+ becomes resistant to Cd2+ and proliferates despite the presence of this metal. The accumulation of the sulfur metabolites gamma-glu-cys, glutathione and phytochelatin 2 displayed cyclic patterns that were disturbed by a challenge with Cd2+. We observed a p38 MAPK-like activity that was stimulated by acute or chronic heavy metal exposure, and its inhibition by SB203580 slightly diminished the accumulation of sulfur compounds. p38 MAPK inhibition also affected basal levels of glutathione in either pretreated or control cells. Thus, it appears that p38 MAPK mediates redox stress component of the signal pathway induced by heavy metals.

Heavy Metals Content in Paraphilometroides nemipteri from South China Sea may Influence Level of Glutathione and P38 Protein Expression

“…According to Rios-Barrera et al (2008), heavy metals such as cadmium and mercury exhibited p38 MAPK activity that mediates redox stress of the MAPKK signal pathways in Euglena gracilis. P38 MAPK pathways was discovered to be associated with apoptosis, stress responses and immunity (Johnson & Lapadat 2002).…”

“…On the other hand, p38 MAPK acts as a signal transduction component of heavy metals stress that mediates redox stress component of signal induction pathway when exposed to heavy metals (Rios-Barrera et al 2008). A review by Ventura-Lima et al (2011), reported that arsenic in aquaporins could affect signalling pathways by activating proteins such as ERK2, p38 and JNK as demonstrated in mammals.…”