Dopamine modulates hemocyte phagocytosis via a D1-like receptor in the rice stem borer, Chilo suppressalis

Abstract

Dopamine (DA) is a signal moiety bridging the nervous and immune systems. DA dysregulation is linked to serious human diseases, including addiction, schizophrenia, and Parkinson’s disease. However, DA actions in the immune system remain incompletely understood. In this study, we found that DA modulates insect hemocyte phagocytosis using hemocytes prepared from the rice stem borer (RSB), Chilo suppressalis. We investigated whether insect hemocytes are capable of de novo DA production. Here we show that exposing hemocytes to lipopolysaccharide (LPS) led to induction of DA-generating enzymes. Exogenous DA induced rapid phosphorylation of extracellular signal-regulated kinase (ERK) in naïve hemocytes. Activation of ERK was inhibited by preincubating with a DOP1 receptor antagonist. Thus, DA signaling via the DOP1 receptor may contribute to early hemocyte activation. DA synthesized and released from hemocytes may act in an autocrine mechanism to stimulate or maintain phagocytic activity. Consistent with this hypothesis, we found that inhibition of DA synthesis with α-methyl-DL-tyrosine methyl ester hydrochloride or blockage of DOP1 receptor with antagonist SCH23390 impaired hemocyte phagocytosis. Topical DA application also significantly decreased RSB mortality following challenge with the insect pathogenic fungus, Beauveria bassiana. We infer that a DA-dependent signaling system operates in hemocytes to mediate phagocytotic functions.

Serotonin modulates insect hemocyte phagocytosis via two different serotonin receptors

“…The diluted hemolymph was added to 12-well tissue culture plates (Nunc, Roskilde, Denmark) at a density of 2× 10 6 cells per well. Hemocytes were treated with 100 ng/ml LPS ( Escherichia coli 0111:B4; Sigma Aldrich) for 15 min, 1 hr, 2 hr, and 4 hr ( Ngkelo et al, 2012 ; Wu et al, 2015 ). The hemocyte culture was collected and centrifugated.…”

Altered immunity in crowded Mythimna separata is mediated by octopamine and dopamine

“…5-HT mediates haemocyte phagocytosis through the receptors 5-HT1B and 5-HT2B 15 . The dopamine-dependent signalling system operates in haemocytes to mediate phagocytic functions 16 . N-β-alanyldopamine synthase was induced in the mealworm, Tenebrio molitor , and in the medfly, Ceratitis capitata , by infection with Escherichia coli 17 .…”

Identification and expression profiles of neuropeptides and their G protein-coupled receptors in the rice stem borer Chilo suppressalis

“…This insect causes serious crop losses every year, particularly in China because of the prevalence of rice cultivation and the popularization of hybrid varieties 6 . C. suppressalis is a lepidopteran pest that represents a diverse and important group of agricultural insect pests that cause widespread economic damage to food and fiber crop plants, fruit trees, forests, and stored grains 7 8 9 . Currently, chemical pesticides represent the primary method of controlling insect pests, and the excessive use of these chemicals in the field has led to the development of insecticide resistance 10 .…”