Cyclic-AMP Mediated Regulation of ABCB mRNA Expression in Mussel Haemocytes

Abstract

BackgroundThe multixenobiotic resistance system (MXR) allows aquatic organisms to cope with their habitat despite high pollution levels by over-expressing membrane and intracellular transporters, including the P-glycoprotein (Pgp). In mammals transcription of the ABCB1 gene encoding Pgp is under cAMP/PKA-mediated regulation; whether this is true in mollusks is not fully clarified.Methodology/Principal FindingscAMP/PKA regulation and ABCB mRNA expression were assessed in haemocytes from Mediterranean mussels (Mytilus galloprovincialis) exposed in vivo for 1 week to 0.3 ng/L fluoxetine (FX) alone or in combination with 0.3 ng/L propranolol (PROP). FX significantly decreased cAMP levels and PKA activity, and induced ABCB mRNA down-regulation. FX effects were abolished in the presence of PROP. In vitro experiments using haemocytes treated with physiological agonists (noradrenaline and serotonin) and pharmacological modulators (PROP, forskolin, dbcAMP, and H89) of the cAMP/PKA system were performed to obtain clear evidence about the involvement of the signaling pathway in the transcriptional regulation of ABCB. Serotonin (5-HT) decreased cAMP levels, PKA activity and ABCB mRNA expression but increased the mRNA levels for a putative 5-HT1 receptor. Interestingly, 5-HT1 was also over-expressed after in vivo exposures to FX. 5-HT effects were counteracted by PROP. Forskolin and dbcAMP increased PKA activity as well as ABCB mRNA expression; the latter effect was abolished in the presence of the PKA inhibitor H89.ConclusionsThis study provides the first direct evidence for the cAMP/PKA-mediated regulation of ABCB transcription in mussels.

Neurotoxicological effects on marine mussel Mytilus galloprovincialis caged at petrochemical contaminated areas (eastern Sicily, Italy): 1H NMR and immunohistochemical assays

“…As expected, in mussels caged at the petrochemical site of Priolo AChE immunopositivity was reduced, and limited almost solely to hemocytes. In marine mussels, hemocytes possess a complex cell signaling network with high homology with that of vertebrates, that allows them to modulate their own functions (Humphries and Yoshino, 2003;Franzellitti and Fabbri, 2013). However, little it is known on the physiological roles of these signaling pathways in mussel hemocytes.…”

Renal nerve stimulation leads to the activation of the Na+/H+exchanger isoform 3 via angiotensin II type I receptor

“…We measured urinary angiotensinogen (AGT) using an ELISA (Rat Total Angiotensinogen Assay Kit, Clontech Laboratories) according to the manufacturer's instructions and plasma AGT via immunoblotting. Urinary cAMP was measured by using an ELISA kit (DetectXTM direct cAMP enzyme immunoassay kit, Arbor Assays) according to the manufacturer's instructions (21).…”

Human pharmaceuticals in the marine environment: Focus on exposure and biological effects in animal species

“…Nevertheless, the increases in cAMP levels and PKA activities in the mantle/gonads of propranolol‐exposed mussels observed in same study support an indirect stimulation of propranolol by acting as a 5‐HT1 receptor antagonist. It is worth noting that transcripts encoding 5‐HT1 receptors have been detected in several mussel tissues, including mantle/gonads . Furthermore, Garnerot et al showed that serotoninergic fibers are apparently absent or scarce in bivalve digestive gland, whereas a high concentration of these fibers is detected in gonads.…”

“…As recently reviewed , the cAMP‐dependent pathway is well known for regulating several functions in mollusks and, among others, the nucleotide modulates the availability of mantle glycogen as fuel for gonad maturation. Furthermore, recent investigations have suggested a role of cAMP in the control of key cytoprotective mechanisms providing an adaptive advantage for marine bivalves to cope with environmental challenges . Therefore, conservation of therapeutic effects of pharmaceuticals targeting cell‐signaling mediators may impair the ability of organisms to cope with environmental stressors, thus potentially undermining their fitness.…”