Transcriptome sequencing and metabolite analysis reveal the single and combined effects of microplastics and di-(2-ethylhexyl) phthalate on Peneaus vannamei.

Due to the rising usage of plastics, plastic debris are present throughout marine ecosystems and detrimentally affects marine biota. Additionally, plastics likely result in elusive toxicity effects due to addition of plasticizers. The aim of the present study was to reveal the potential effects and mechanism of microplastics (MPs), di-(2-ethylhexyl) phthalate (DEHP) and copollution of MPs and DEHP (MPs-DEHP) on Peneaus vannamei (P. vannamei) juveniles regarding oxidative stress, transcriptomics and metabolomics. MPs, DEHP and MPs-DEHP significantly induced the activities of superoxide dismutase (SOD) and catalase (CAT); MPs and DEHP have an antagonistic effect for malondialdehyde (MDA); suggesting that disorders of the antioxidant defence systems. 13, 133 and 58 differentially expressed genes and 21, 82 and 39 differentially expressed metabolites were responsible for the distinction of MPs, DEHP and MPs-DEHP groups, respectively. The combination of transcriptomic and metabolomic analyses showed that MPs, DEHP and MPs-DEHP exposure disturbed amino acid and lipid metabolism, and further induced inflammatory responses and dysfunction of purine metabolism. Furthermore, the presence of MPs might alleviate the biotoxicity of DEHP in P. vannamei. These findings provide new insights into the single and combined toxicological effects of MPs and additives for marine biota.

Ontogenetic and sexual differences of thermal biology and locomotor performance in a lacertid lizard, Eremias multiocellata.

A viviparous lizard, Eremias multiocellata, was used to investigate the possible sexual and ontogenetic effects on selected body temperature, thermal tolerance range and the thermal dependence of locomotor performance. We show that adults are sexually dimorphic and males have larger bodies and heads than females. Adults selected higher body temperatures (34.5 vs. 32.4°C) and could tolerate a broader range of body temperatures (8.1-46.8 vs. 9.1-43.1°C) than juveniles. The sprint speed and maximum sprint distance increased with temperature from 21°C to 33°C, but decreased at 36°C and 39°C in both juveniles and adults. Adults ran faster and longer than juveniles at each tested temperature. Adult locomotor performance was not correlated with snout-vent length (SVL) or sex, and sprint speed was positively correlated with hindlimb length. Juvenile locomotor performance was positively correlated with both SVL and hindlimb length. The ontogenetic variation in selected body temperature, thermal tolerance and locomotor performance in E. multiocellata suggests that the effects of morphology on temperature selection and locomotor performance vary at different ontogenetic stages.

Intrathecal apelin-13 produced different actions in formalin test and tail-flick test in mice.

Apelin was identified as natural ligand for APJ, a G protein-coupled receptor. APJ is expressed in spinal cord and dorsal root ganglion. This study was designed to investigate the effects and mechanisms of intrathecally (i.t.) administered apelin-13 on nociceptive response in formalin test and tail-flick test. In formalin test, i.t. injection of apelin-13 (0.3-3 nmol/mouse) had no effect on the nociceptive response in either acute phase (0-10 min) or interphase (10-20 min), but significantly produced hyperalgesic effect in late phase (20-30 min) at the dose of 3 nmol/mouse. The APJ receptor antagonist apelin-13(F13A) and GABAA receptor antagonist bicuculline methiodide, but not opioid receptor antagonist naloxone, significantly blocked the hyperalgesia caused by apelin-13 in late phase, indicating that i.t. apelin-13- induced hyperalgesia was mediated by APJ and GABAA receptor, rather than opioid receptor. However, in tail-flick test, i.t. injected apelin-13 (1 and 3 nmol/mouse) induced a significant antinociceptive effect, which was significantly antagonized by apelin-13(F13A) and naloxone, suggesting APJ and opioid receptor were involved in the antinociception of spinal apelin-13.

Supraspinal antinociceptive effect of apelin-13 in a mouse visceral pain model.

Apelin, as the endogenous ligand of the APJ receptor, is a novel identified neuropeptide whose biological functions are not fully understood. APJ receptor mRNA was found in several brain regions related to descending control system of pain, such as amygdala, hypothalamus and dorsal raphe nucleus (DRN). The present study was designed to determine whether supraspinal apelin-13 may produce antinociceptive effect observed in the acetic acid-induced writhing test, a model of visceral pain. Apelin-13 not only significantly produced preemptive antinociception at the dose of 0.3, 0.5, 1 and 3 µg/mouse when injected intracerebroventricularly (i.c.v.) before acetic acid, but also significantly induced antinociception at a dose of 0.5, 1 and 3 µg/mouse when injected i.c.v. after acetic acid. And i.c.v. apelin-13 did not influence 30-min locomotor activity counts in mice. Intrathecal (i.t.) administration of apelin-13 (1 and 3 µg/mouse) significantly decreased the number of writhes, however, intraperitoneal (i.p.) injection of apelin-13 (10-100 µg/mouse) had no effect on the number of writhes in the writhing test. The specific APJ receptor antagonist apelin-13(F13A), no-specific opioid receptor antagonist naloxone and µ-opioid receptor antagonist ß-funaltrexamine hydrochloride (ß-FNA) could significantly antagonize the antinociceptive effect of i.c.v. apelin-13, suggesting APJ receptor and µ-opioid receptor are involved in this process. Central low dose of apelin-13 (0.3 µg/mouse, i.c.v.) could significantly potentiate the analgesic potencies of modest and even relatively ineffective doses of morphine administrated at supraspinal level. This enhanced antinociceptive effect was reversed by naloxone, suggesting that the potentiated analgesic response is mediated by opioid-responsive neurons.

Intracerebroventricular administration of neuronostatin delays gastric emptying and gastrointestinal transit in mice.

Neuronostatin is a 13-amino acid amidated peptide widely distributed in various organs including gastrointestinal tract. However, the effect of neuronostatin on gastrointestinal motility has not been well characterized. In the present work, effects of central administration of neuronostatin on gastric emptying and gastrointestinal transit were investigated. The results indicated that intracerebroventricular (i.c.v.) administration of neuronostatin (1, 5, 10 or 20nmol/mouse) delayed gastric emptying and gastrointestinal transit in a dose-related manner in mice. The effects were significantly reversed by melanocortin 3/4 receptor antagonist SHU9119 or classical opioid receptor antagonist naloxone, suggesting that the central melanocortin system and opioid system may be involved in the gastrointestinal effects elicited by i.c.v. administration of neuronostatin. In addition, we found that C-terminal amidation modification of neuronostatin is essential to exert its gastrointestinal effects. These results indicated that neuronostatin may play an important role in regulating gastrointestinal function.

Central apelin-13 inhibits food intake via the CRF receptor in mice.

Apelin, the novel identified peptide, is the endogenous ligand for the APJ. Previous studies have reported the effect of apelin on food intake, however the action of acute central injected apelin on food intake in mice remains unknown. The present study was designed to investigate the mechanism as well as the effect of central apelin-13 on food intake in mice. During the dark period, the cumulative food intake was significantly decreased at 4h after the intracerebroventricular (i.c.v.) injection of 1 and 3µg/mouse apelin-13 and the period food intake was significantly reduced during 2-4h after treatment. In the fasted mice, the cumulative food intake was significantly decreased at 2 and 4h after injection of 3µg/mouse apelin-13. The cumulative water intake was significantly reduced by apelin-13 (3µg/mouse) at 4h after injection in freely feeding and fasted mice. However, during light period, apelin-13 had no influence on food and water intake in freely feeding mice. The APJ receptor antagonist apelin-13(F13A) (6µg/mouse) and the corticotrophin-releasing factor (CRF) receptor antagonist α-helical CRF(9-41) (3µg/mouse) could reverse the inhibitory effect on cumulative food intake/0-4h induced by apelin-13 (3µg/mouse) in freely feeding mice during the dark period, whereas the anorexic effect could not be antagonized by the arginie vasopressin (AVP) receptor antagonist deamino(CH(2))(5)Tyr(Me)AVP (0.5µg/mouse). Taken together, these results suggest that central apelin-13 inhibits food intake in mice and it seems that APJ receptor and CRF receptor, but not AVP receptor, might be involved in this process.

Neuronostatin induces hyperalgesia in formalin test in mice.

Neuronostatin, a newly identified peptide encoded by the somatostatin (SST) gene, was proved to produce significant antinociceptive effect in mouse tail immersion test. However, the effect of neuronostatin on tonic pain was still not clear. The aim of this study was to investigate the effect of neuronostatin in the formalin test and its possible mechanism. We found that intracerebroventricular (i.c.v.) administration of neuronostatin (1, 3, 6, 12nmol/mouse) increased licking in a dose-related manner during the late phase, but did not affect the early phase of formalin test in mice. In addition, the hyperalgesic effect during the late phase was completely reversed by melanocortin 3/4 receptor antagonist SHU9119 (50pmol/mouse) or opioid receptor antagonist naloxone (5nmol/mouse), but not GABAA receptor antagonist bicuculline (1086pmol/mouse). These data suggested that the hyperalgesic response induced by neuronostatin was dependent upon the central melanocortin system and endogenous opioid system. In conclusion, these results indicated that neuronostatin may be a new neuropeptide with important role in the modulation of acute and tonic pain.