Downregulation of GRK6 in arcuate nucleus promotes chronic visceral hypersensitivity via NF-κB upregulation in adult rats with neonatal maternal deprivation

Abstract

Aims The arcuate nucleus is a vital brain region for coursing of pain command. G protein-coupled kinase 6 (GRK6) accommodates signaling through G protein-coupled receptors. Studies have demonstrated that GRK6 is involved in inflammatory pain and neuropathic pain. The present study was designed to explore the role and the underlying mechanism of GRK6 in arcuate nucleus of chronic visceral pain. Methods Chronic visceral pain of rats was induced by neonatal maternal deprivation and evaluated by monitoring the threshold of colorectal distension. Western blotting, immunofluorescence, real-time quantitative polymerase chain reaction techniques, and Nissl staining were employed to determine the expression and mutual effect of GRK6 with nuclear factor κB (NF-κB). Results Expression of GRK6 in arcuate nucleus was significantly reduced in neonatal maternal deprivation rats when compared with control rats. GRK6 was mainly expressed in arcuate nucleus neurons, but not in astrocytes, and a little in microglial cells. Neonatal maternal deprivation reduced the percentage of GRK6-positive neurons of arcuate nucleus. Overexpression of GRK6 by Lentiviral injection into arcuate nucleus reversed chronic visceral pain in neonatal maternal deprivation rats. Furthermore, the expression of NF-κB in arcuate nucleus was markedly upregulated in neonatal maternal deprivation rats. NF-κB selective inhibitor pyrrolidine dithiocarbamate suppressed chronic visceral pain in neonatal maternal deprivation rats. GRK6 and NF-κB were expressed in the arcuate nucleus neurons. Importantly, overexpression of GRK6 reversed NF-κB expression at the protein level. In contrast, injection of pyrrolidine dithiocarbamate once daily for seven consecutive days did not alter GRK6 expression in arcuate nucleus of neonatal maternal deprivation rats. Conclusions Present data suggest that GRK6 might be a pivotal molecule participated in the central mechanisms of chronic visceral pain, which might be mediated by inhibiting NF-κB signal pathway. Overexpression of GRK6 possibly represents a potential strategy for therapy of chronic visceral pain.

Upregulation of Spinal ASIC1 and NKCC1 Expression Contributes to Chronic Visceral Pain in Rats

“…The CRD threshold of NMD rats was significantly reduced when compared with CON ( Figure 1A , *** P < 0.001, Tukey post hoc test following two-way repeated-measures ANOVA). The data confirms the idea again that NMD might develop chronic visceral hyperalgesia in adult rats (Xiao et al, 2016 ; Du et al, 2019 ; Li et al, 2020 ).…”

“…Chronic visceral pain was induced by NMD, as described previously (Du et al, 2019 ; Li et al, 2020 ). In short, from the 2 to 15 days of birth, the newborn SD male pups of the NMD group were placed in a separate box with an electric blanket for 3 h. After the separation period, the pups were placed back with their dams.…”

“…Visceral hypersensitivity is determined by the colorectal distention (CRD) threshold as described previously (Du et al, 2019 ; Li et al, 2020 ). In brief, after the rats were lightly anesthetized with isoflurane, a self-made soft and flexible balloon (4 cm) was inserted into the rectum and colon 6 cm from the rat anus.…”

“…In the present study, we used the well-established visceral hypersensitivity rat model, which is a suitable animal model to study pathophysiological characteristics of IBS-like (Du et al, 2019 ; Li et al, 2020 ), to verify the hypothesis that the upregulation of ASIC1 in the spinal dorsal horn contributes to the enhanced expression of NKCC1, thereby enhancing excitatory synaptic transmission of spinal dorsal horn neurons and resulting in chronic visceral pain in neonatal maternal deprivation (NMD) rats.…”

Upregulation of spinal ASIC1 by miR‐485 mediates enterodynia in adult offspring rats with prenatal maternal stress

“…Recent studies have also shown that changes in expression and functions of key ion channels and receptors in extrinsic sensory neurons play an important role in the abnormal pain of gastrointestinal diseases. [14][15][16] Acid-sensing ion channels (ASICs) are a class of cation channels that are directly activated by extracellular acids and belong to the degenerate protein, epithelial Na + ion channel superfamily (DEG/ENaC), which are widely distributed in central and peripheral nervous systems. 17 ASICs are divided into at least six isoforms: ASIC1a, ASIC1b, ASIC2a, ASIC2b, ASIC3, and ASIC4.…”