Significance of DopEcR, a G-protein coupled dopamine/ecdysteroid receptor, in physiological and behavioral response to stressors

Organisms respond to various environmental stressors by modulating physiology and behavior to maintain homeostasis. Steroids and catecholamines are involved in the highly conserved signaling pathways crucial for mounting molecular and cellular events that ensure immediate or long-term survival under stress conditions. The insect dopamine/ecdysteroid receptor (DopEcR) is a dual G-protein coupled receptor for the catecholamine dopamine and the steroid hormone ecdysone. DopEcR acts in a ligand-dependent manner, mediating dopaminergic signaling and unconventional "nongenomic" ecdysteroid actions through various intracellular signaling pathways. This unique feature of DopEcR raises the interesting possibility that DopEcR may serve as an integrative hub for complex molecular cascades activated under stress conditions. Here, we review previously published studies of Drosophila DopEcR in the context of stress response and also present newly discovered DopEcR loss-of-function phenotypes under different stress conditions. These findings provide corroborating evidence that DopEcR plays vital roles in responses to various stressors, including heat, starvation, alcohol, courtship rejection, and repeated neuronal stimulation in Drosophila. We further discuss what is known about DopEcR in other insects and DopEcR orthologs in mammals, implicating their roles in stress responses. Overall, this review highlights the importance of dual GPCRs for catecholamines and steroids in modulating physiology and behavior under stress conditions. Further multidisciplinary studies of Drosophila DopEcR will contribute to our basic understanding of the functional roles and underlying mechanisms of this class of GPCRs.

Factors that Differentially Affect Daytime and Nighttime Sleep in Drosophila melanogaster

Rest in the fruit fly Drosophila melanogaster has key characteristics of mammalian sleep and is thus considered as a fly version of sleep. Drosophila sleep has been studied extensively, with the aim of gaining fundamental insights into the evolutionarily conserved functions of sleep as well as the mechanisms that regulate it. An interesting question that has not yet been addressed is whether fly sleep can be classified into distinct sleep types, each having particular biological roles – like rapid eye movement (REM) and non-REM sleep in birds and mammals. Typically, Drosophila sleep displays a bimodal pattern, consisting of distinct daytime and nighttime components. Notably, daytime and nighttime sleep differ with respect to several qualities, such as sleep-bout lengths and arousal thresholds. In this short review, we describe several genetic and environmental factors that differentially affect daytime and nighttime sleep, highlighting the observations suggesting the notion that these temporally distinct components of Drosophila sleep may have unique biological functions and be regulated by different homeostatic regulatory mechanisms.

Targeting adenosine monophosphate-activated protein kinase (AMPK) in preclinical models reveals a potential mechanism for the treatment of neuropathic pain

Neuropathic pain is a debilitating clinical condition with few efficacious treatments, warranting development of novel therapeutics. We hypothesized that dysregulated translation regulation pathways may underlie neuropathic pain. Peripheral nerve injury induced reorganization of translation machinery in the peripheral nervous system of rats and mice, including enhanced mTOR and ERK activity, increased phosphorylation of mTOR and ERK downstream targets, augmented eIF4F complex formation and enhanced nascent protein synthesis. The AMP activated protein kinase (AMPK) activators, metformin and A769662, inhibited translation regulation signaling pathways, eIF4F complex formation, nascent protein synthesis in injured nerves and sodium channel-dependent excitability of sensory neurons resulting in a resolution of neuropathic allodynia. Therefore, injury-induced dysregulation of translation control underlies pathology leading to neuropathic pain and reveals AMPK as a novel therapeutic target for the potential treatment of neuropathic pain.

Does occupational exposure to brown coal dust cause a decline in lung function?

OBJECTIVES

To determine if the rate of change in forced expiratory volume in one second (FEV1) in subjects with high exposure to Latrobe Valley brown coal dust was significantly greater than the rate of change among subjects with low exposure.

METHODS

A retrospective dynamic cohort design with variable time windows. This study was conducted over a period of 14 years from 1980 to 1994 and used data collected by the State Electricity Commission (SEC) Lung Function Unit for an asbestos surveillance programme. The subjects were exposed to low, medium, or high levels of coal dust. Basic spirometry with wedge bellows spirometers was used to assess lung function. A general linear model (GLM) was used to assess the effects of smoking and exposure to coal dust upon the change in forced expiratory volume in one second (FEV1) while adjusting for age and height.

RESULTS

The mean (95% confidence interval (95% CI) rate of decline in FEV1 was 40 (36 to 44) ml/year. Age was a significant predictor of change. A significant effect was found for smoking (P = 0.02) and for exposure to coal dust (P = 0.008). The only significant difference with exposure to coal dust was between the high and mixed exposure categories.

CONCLUSION

There is no convincing evidence of excessive decline in FEV1 with exposure to coal dust > 0.75 mg/m3. The absence of a dose response relation provides some evidence against a causal relation. On the basis of this study, reduction of the exposure standards currently applied to brown coal dust in the Victorian electricity industry is not warranted to prevent respiratory disease.