Novel protein kinase C participates catecholamine biosynthesis and immunocompetence modulation in haemocytes of Litopenaeus vannamei

Ameliorative role of Syzygium aromaticum aqueous extract on synaptosomal tyrosine hydroxylase activity, oxidative stress parameters, and behavioral changes in lead-induced neurotoxicity in mice

This study reports the protective role of the aqueous extract of Syzygium aromaticum (ESA) against lead (Pb)-induced neurotoxicity in mice. Thirty male mice weighing between 18 g and 25 g were randomly divided into five groups. (1) Group 1 (control group), (2) group 2 (Pb-test group): was administered with a solution containing 0.1% (w/v) of lead acetate (PbAc), (3) group 3 (ESA + Pb100 group): was administered with 0.1% (w/v) of PbAc followed by 100 mg/kg of S. aromaticum extract by gavage, (4) group 4 (ESA + Pb200): was administered with 0.1% (w/v) of PbAc followed by 200 mg/kg of S. aromaticum extract, and (5) group 5 (ESA-group): was administered with 100 mg/kg of S. aromaticum. Level of lead was determined by atomic absorption spectroscopy. Cerebral cortex synaptosomes prepared from mice administered orally with lead-acetate shown a significantly increased (p < .05) in tyrosine hydroxylase and protein carbonyl level and significantly decreased (p < .05) superoxide dismutase, glutathione reductase, and glutathione transferase activities. Also, there was a significant increase in brain lead concentration level, however, it was observed that S. aromaticum significantly reduced (p < .05) the level of lead at all tested doses. S. aromaticum rescued cerebral cortex synaptosomes from lead-induced neurotoxicity by relieving oxidative stress and abating elevated tyrosine hydroxylase activity. Moreover, S. aromaticum at the different dose grade (100 mg and 200 mg) abrogated the loss of motor performance in mice groups induced with lead. Altogether, our findings showed that S. aromaticum possesses antioxidant and neuro-modulatory potential against lead-induced neuronal damage. PRACTICAL APPLICATIONS: Environmental pollution with heavy metals is a known public health concern and their incremental concentrations in soil and water have risen to an unprecedented degree. Lead is one of the top 10 contaminants on the WHO's list of substances of greatest public health concern that impact the brain. However, exogenous natural bioactive supplements molecules could be one of the remedies to reduce Pb-induced toxicity. Our findings indicate therefore that, S. aromaticum could be a good fit for lowering Pb neurotoxicity and could be suggested as a neuroprotective molecule against neurodegenerative diseases involving catecholaminergic dysfunction induced by metallic elements.

Transcriptomic analysis of gills in nitrite-tolerant and -sensitive families of Litopenaeus vannamei

Nitrite stress is a major environmental factor that limits aquatic animal growth, reproduction and survival. Even so, some shrimps still can withstand somewhat high concentrations of nitrite environment. However, few studies have been conducted about the tolerance molecular mechanism of Litopenaeus vannamei in the high concentration nitrite. To identify the genes and pathways involved in the regulation of nitrite tolerance, we performed comparative transcriptomic analysis in the L. vannamei nitrite-tolerant (NT) and nitrite-sensitive (NS) families, and untreated shrimps were used as the control group. After 24 h of nitrite exposure (NaNO₂, 112.5 mg/L), a total of 1521 and 868 differentially expressed genes (DEGs) were obtained from NT compared with NS and control group, respectively. Functional enrichment analysis revealed that most of these DEGs were involved in immune defense, energy metabolism processes and endoplasmic reticulum (ER) stress. During nitrite stress, energy metabolism in NT was significantly enhanced by activating the related genes expression of oxidative phosphorylation (OXPHOS) pathway and tricarboxylic acid (TCA) cycle. Meanwhile, some DEGs involved in innate immunity- related genes and pathways, and ER stress responses also were highly expressed in NT. Therefore, we speculate that accelerated energy metabolism, higher expression of immunity and ER related genes might be the important adaptive strategies for NT in relative to NS under nitrite stress. These results will provide new insights on the potential tolerant molecular mechanisms and the breeding of new varieties of nitrite tolerant L. vannamei.

In vivo study of a novel protein kinase C that mediates immunocompetence and catecholamine biosynthesis in hemocytes of Litopenaeus vannamei by using its potential competitive inhibitor, bisindolylmaleimide I

This study applied bisindolylmaleimide I (BSM), a pharmacological competitive inhibitor of protein kinase C (PKC) enzymatic activity, at 1.25 pmol shrimp^-1 for 60 min to investigate the potential involvement of PKC in signal transduction pathways in the hemocytes of Litopenaeus vannamei. A novel PKC in L. vannamei (LvnPKC) was identified and characterized and was determined to be involved in mediating the neuroendocrine-immune regulatory network. The hemocytes of L. vannamei that receive BSM exhibit significantly decreased PKC activity and LvnPKC gene and protein expression levels. Furthermore, the total hemocyte count, hyaline cells, and semigranular cells increased significantly along with significant decreases in granular cells, and meanwhile, the significantly increased phenoloxidase activity, respiratory bursts, superoxide dismutase (SOD) activity, phagocytic activity, and neutrophil extracellular trap were observed; however, phagocytic activity decreased significantly. In a molecular model, the gene expressions of lipopolysaccharide- and β-1,3-glucan-binding protein, peroxinectin, cytosolic manganese SOD, mitochondrial manganese SOD, and copper/zinc SOD in the hemocytes of L. vannamei that had received BSM decreased significantly, but prophenoloxidase I increased significantly. In catecholamine biosynthesis, tyrosine, dopamine, and norepinephrine decreased significantly in the hemocytes of L. vannamei that had received BSM, and l-dihydroxyphenylalanine increased. Moreover, tyrosine hydroxylase (TH) activity increased significantly, whereas TH and dihydroxyphenylalanine decarboxylase gene expression decreased significantly. These findings suggest that BSM inhibits PKC activity in hemocytes in which LvnPKC gene and protein expression are also inhibited. Additionally, the hemocytes' immunocompetence, including their prophenoloxidase and antioxidant systems, phagocytic activity, and catecholamine biosynthesis, was disrupted, confirming the roles of LvnPKC in mediating the neuroendocrine-immune regulatory network in hemocytes.

Role of novel protein kinase C in neuroendocrine-immune regulatory network in haemocytes of Litopenaeus vannamei: An in vitro approach

Shrimp lack adaptive immune systems and mainly rely on the cellular and humoral defences, involving the haemocytes (functionally analogous to vertebrate leukocytes) in non-self matter recognition, elimination, and in downstream coagulation. Furthermore, the linkage between stress-induced catecholamine (CA), a class of biogenic amines (BAs), releasing and immunological responses has been detected in shrimp. Varied isotypes of protein kinase C (PKC) regulate multiple cellular processes following their specific location and distribution within the cells, and a novel PKC identified in Litopenaeus vannamei (termed as LvnPKC) is proposed to mediate signaling transduction of immunocompetence and BA biosynthesis. In the present study, we analyzed the effects of the LvnPKC-silenced haemocytes by co-incubating with its dsRNA on the immune responses specific to prophenoloxidase (proPO) and antioxidant systems as well as phagocytic activity. In addition, the capability of haemocytes to produce BAs was assessed. The results revealed that LvnPKC-silenced haemocytes can induce interference in phenoloxidase and superoxide dismutase activities, respiratory bursts, and phagocytic activity; meanwhile, the disturbed gene expressions of proPO activating enzyme, proPOII, lipopolysaccharide- and β-1,3-glucan-binding protein, and cytosolic manganese superoxide dismutase were detected. The same deviated pattern was observed in tyrosine, dopamine, and norepinephrine levels, and in dopamine β-hydroxylase (DBH) activity and gene expressions of tyrosine hydroxylase, DOPA decarboxylase, and DBH involving in BA biosynthesis. Taken together, these results suggest that the immunocompetence and BA biosynthesis of haemocytes can be mediated via LvPKC signaling transduction, which proved the presence of a neuroendocrine-immune regulatory network in haemocytes.