Multiple roles for protein kinase C in gastropod embryogenesis

c-Raf participates in adaptive immune response of Nile tilapia via regulating lymphocyte activation

RAF proto-oncogene serine/threonine-protein kinase (c-Raf) is a MAP kinase kinase kinase (MAPKKK) that participates in the Erk1/2 pathway and plays an important role in lymphocyte activation. However, the study on how c-Raf regulates adaptive immunity in non-mammal is still limited. In present study, based on analysis of sequence characteristics of c-Raf from Oreochromis niloticus (On-c-Raf), we investigated its regulation roles on teleost lymphocyte activation. The On-c-Raf was highly conserved during evolution, which was composed of a Raf-like Ras-binding domain (RBD), a protein kinase C conserved region 1 (C1) domain and a serine/threonine protein kinase catalytic (S_TKc) domain. Its mRNA showed a wide distribution in tissues of O. niloticus and with the highest expression in gill. After Aeromonas hydrophila infection, during the adaptive immune stage transcription level of On-c-Raf was significantly upregulated on day 8, but came back to original level on day 16 and 30, suggesting the potential involvement of On-c-Raf in primary response but not memory formation. Furthermore, On-c-Raf mRNA in leukocytes of Nile tilapias was obviously induced by in vitro stimulation of T cell mitogen PHA. More importantly, in vitro stimulation of lymphocytes agonist PMA augmented phosphorylation level of On-c-Raf in leukocytes detected by western-blot and immunofluorescent. Thus, c-Raf regulated lymphocyte activation of Nile tilapia on both mRNA and phosphorylation level. Together, our results revealed that the c-Raf from teleost Nile tilapia engaged in adaptive immune response by regulating lymphocytes activation. Since the regulatory mechanism of lymphocyte-mediated adaptive immunity is largely unknown in teleost, our study provided important evidences to understand teleost adaptive immunity, and also shed a novel perspective for the evolution of adaptive immune system.

Embryonic exposure to model naphthenic acids delays growth and hatching in the pond snail Lymnaea stagnalis

Naphthenic acids (NAs), a class of structurally diverse carboxylic acids with often complex ring structures and large aliphatic tail groups, are important by-products of many petrochemical processes including the oil sands mining activity of Northern Alberta. While it is evident that NAs have both acute and chronic harmful effects on many organisms, many aspects of their toxicity remain to be clarified. Particularly, while substantive data sets have been collected on NA toxicity in aquatic prokaryote and vertebrate model systems, to date, nothing is known about the toxic effects of these compounds on the embryonic development of aquatic invertebrate taxa, including freshwater mollusks. This study examines under laboratory conditions the toxicity of NAs extracted from oil sands process water (OSPW) and the low-molecular weight model NAs cyclohexylsuccinic acid (CHSA), cyclohexanebutyric acid (CHBA), and 4-tert-butylcyclohexane carboxylic acid (4-TBCA) on embryonic development of the snail Lymnaea stagnalis, a common freshwater gastropod with a broad Palearctic distribution. Evidence is provided for concentration-dependent teratogenic effects of both OSPW-derived and model NAs with remarkably similar nominal threshold concentrations between 15 and 20 mg/L and 28d EC₅₀ of 31 mg/L. In addition, the data provide evidence for substantial toxicokinetic differences between CHSA, CHBA and 4-TBCA. Together, our study introduces Lymnaea stagnalis embryonic development as an effective model to assay NA-toxicity and identifies molecular architecture as a potentially important toxicokinetic parameter in the toxicity of low-molecular weight NA in embryonic development of aquatic gastropods.

Effect of PMA-induced protein kinase C activation on development and apoptosis in early zebrafish embryos

Protein kinase C (PKC) isoforms have been implicated in several key steps during early development, but the consequences of xenobiotic-induced PKC activation during early embryogenesis are still unknown. In this study, zebrafish embryos were exposed to a range of phorbol 12-myristate 13-acetate (PMA) concentrations (0-200μg/L) at different time points after fertilization. Results showed that 200μgPMA/L caused development of yolk bags, cardiac edema, slow blood flow, pulsating blood flow, slow pulse, elongated heart, lack of tail fins, curved tail, and coagulation. PMA exposure decreased survival rate of the embryos starting within the first 24h and becoming more pronounced after prolonged exposure (96h). PMA increased the number of apoptotic cells in the brain region as demonstrated by acridine orange staining and caused up-regulation of caspase 9 (casp9) and p53 up-regulated modulator of apoptosis (puma) mRNA in whole embryos. PMA caused oxidative stress in the embryos as demonstrated by decreased mRNA expression of catalase and superoxide dismutase 2. Inhibition of Pkc with GF109203X improved overall survival rate, reduced apoptosis in the brain and decreased expression of casp9 and puma in the PMA-exposed embryos. However, Pkc inhibition neither prevented development of deformities nor reversed oxidative stress in the PMA-exposed embryos. These data suggest that direct over-activation of Pkc during early embryogenesis of zebrafish is associated with apoptosis and decreased survival rate of the embryos.