Skin as the first barrier against external invasions plays an essential role for the survival of amphibians on land. Understanding the genetic basis of skin function is significant in revealing the mechanisms underlying immunity of amphibians. In this study, we de novo sequenced and comparatively analyzed skin transcriptomes from three different amphibian species, Andrias davidianus, Bufo gargarizans, and Rana nigromaculata Hallowell. Functional classification of unigenes in each amphibian showed high accordance, with the most represented GO terms and KEGG pathways related to basic biological processes, such as binding and metabolism and immune system. As for the unigenes, GO and KEGG distributions of conserved orthologs in each species were similar, with the predominantly enriched pathways including RNA polymerase, nucleotide metabolism, and defense. The positively selected orthologs in each amphibian were also similar, which were primarily involved in stimulus response, cell metabolic, membrane, and catalytic activity. Furthermore, a total of 50 antimicrobial peptides from 26 different categories were identified in the three amphibians, and one of these showed high efficiency in inhibiting the growth of different bacteria. Our understanding of innate immune function of amphibian skin has increased basis on the immune-related unigenes, pathways, and antimicrobial peptides in amphibians.

Bupivacaine, a local anaesthetic, is widely applied in the epidural or subarachnoid space to clinically manage acute and chronic pain. However, the underlying mechanisms are complex and unclear. Glycine transporter 1 (GlyT1) in the spinal cord plays a critical role in various pathologic pain conditions. Therefore, we sought to determine whether bupivacaine exerts its analgesic effect by regulating GlyT1 expression and to determine the underlying mechanisms of regulation. Primary astrocytes prepared from the spinal cord of rats were treated with bupivacaine. The protein levels of GlyT1, brain-derived neurotrophic factor (BDNF) and phosphorylated adenosine 5′-monophosphate (AMP)-activated protein kinase α (p-AMPKα) were measured by western blotting or immunofluorescence. In addition, 7,8-dihydroxyflavone (7,8-DHF, BDNF receptor agonist) and AMPK shRNA were applied to verify the relationship between the regulation of GlyT1 by bupivacaine and the p-AMPKα/BDNF signalling pathway. After treatment with bupivacaine, GlyT1 expression was diminished in a concentration-dependent manner, while the expression of BDNF and p-AMPK was increased. Moreover, 7,8-DHF decreased GlyT1 expression, and AMPK knockdown suppressed the upregulation of BDNF expression by bupivacaine. Finally, we concluded that bupivacaine reduced GlyT1 expression in spinal astrocytes by activating the p-AMPKα/BDNF signalling pathway. These results provide a new mechanism for the analgesic effect of intrathecal bupivacaine in the treatment of acute and chronic pain.

Neuraxial anesthesia produces an anesthetic-sparing, sedative effect. The mechanism underlying this effect potentially involves decreased spinal afferent input. However, the neurochemical mechanisms at the spinal level remain unknown. The N-methyl-D-aspartate receptor 2B subunit/calcium-calmodulin-dependent protein kinase II α/cAMP response element-binding protein (NR2B/CaMKIIα/CREB) signaling pathway serves an important role in regulating the transmittance of peripheral noxious stimulation to supraspinal regions in the process of nociception. The present study investigated the effects of intrathecal bupivacaine on the NR2B/CaMKIIα/CREB signaling pathway. Following catheterization, 36 male Sprague-Dawley rats were randomly assigned to a normal saline (NS) or bupivacaine treatment group, in which each rat intrathecally received 20 µl normal saline or 0.5% bupivacaine, respectively. The expression levels of NR2B, CaMKIIα/p-CaMKIIα, and CREB/phosphorylated (p)-CREB in the lumbar spinal cord were investigated by western blotting, reverse transcription-quantitative polymerase chain reaction and immunohistochemistry (IHC). Following bupivacaine treatment, western blot analysis demonstrated that the protein expression levels of NR2B, p-CaMKIIα, and p-CREB in the spinal cord were reduced by approximately 54, 56 and 33%, respectively, compared with NS control rats. Similar alterations in expression were observed by IHC analysis. Additionally, mRNA expression levels of NR2B, CaMKIIα, and CREB were also downregulated following the intrathecal administration of bupivacaine. Therefore, the sedative effect of subarachnoid blockade with bupivacaine possibly occurs through de-afferentation, which may reduce cortical arousal by downregulating the spinal NR2B/CaMKIIα/CREB pathway in vivo, however further investigation is required in order to verify this.

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L e t t e r t o t h e E d i t o rDear Sir, We herein describe an unexpected case of severe perineal pain that gradually developed into urinary incontinence following a single 10-mg intravenous injection of dexamethasone sodium phosphate.A 25-year-old man was scheduled for nasal septal reconstruction and maxillary sinus cyst removal via reconstruction under nasal endoscope. Before the induction of anaesthesia in the operating room, a single 10-mg dose of dexamethasone sodium phosphate (product batch no.: 1208296432, Chen Xin Pharmaceutical Co Ltd, Jining, China) was administered intravenously to the patient. The patient immediately complained of severe itching, burning and numbness, which were confined to the perineal region. General anaesthesia was induced to relieve his discomfort. The patient was extubated at the end of the 1-hour surgery and recovered from the effects of anaesthesia without complaints of discomfort at the perineal region.Urinary incontinence developed 3 hours after surgery, and the patient described his urination as uncontrolled and intermittent, not accompanied by urination urgency and urodynia. Physical examination revealed that the bladder was not filled. The patient refused urethral catheterisation and bladder imaging. Nevertheless, the symptoms and condition gradually improved within 1 hour, and the patient fully recovered 28 hours postoperatively.However, 42 hours after surgery, the patient developed itching and urticaria of the skin on his anterior chest. As this occurrence was thought to be due to drug allergy, the attending doctor administered a 10-mg dose of dexamethasone sodium phosphate for anti-allergy treatment. The discomfort at the perineal region immediately reoccurred and the patient again developed gradual urinary incontinence in the following 3 hours. He recovered within the next 18 hours without any sequelae, and was discharged from the hospital on postoperative Day 4.The mechanism of urinary incontinence is unclear in this case. We suspect that phosphate ester could have led to dysfunction of the pudendal nerve, which controls the sensory perception in the perineal region and urination. Various measures are available to prevent perineal discomfort, including administration of dexamethasone after induction of anaesthesia, administration of fentanyl prior to dexamethasone and dilution of dexamethasone to be given as a slow bolus.(1-3) We opine that corticosteroid phosphate esters play an important role in the development of urinary incontinence. Therefore, careful attention should be paid to the rare adverse effects of dexamethasone sodium phosphate and the prevention of such occurrences.Yours sincerely,