Upregulation of Netrin-1 in the hippocampus mediates the formation of visceral hypersensitivity induced by maternal separation

Abstract

Early adverse life events (EALs), such as maternal separation (MS), can cause visceral hypersensitivity, which is thought to be a key pathophysiological mechanism of irritable bowel syndrome (IBS). Previous studies mainly focused on EALs-induced visceral hypersensitivity in adulthood but did not consider that it may have occurred in the preadult period. We previously found that rats who experienced MS suffered from visceral hypersensitivity starting from the post-weaning period. Moreover, the hippocampus is considered to be critical in regulating the formation of visceral hypersensitivity induced by MS. But the underlying mechanisms throughout different life periods are unclear. In this study, behavioral tests, RNA-seq, lentiviral interference, and molecular biology techniques were applied to investigate the molecular mechanism in the hippocampus underlying MS-induced long-lasting visceral hypersensitivity. It was found that both visceral sensitivity and anxiety-like behaviors were significantly increased in MS rats in post-weaning, prepubertal, and adult periods, especially in the prepubertal period. Subsequently, RNA-seq targeting the hippocampus identified that the expression level of Netrin-1 was significantly increased in all periods, which was further confirmed by quantitative real-time PCR and Western blot. Knocking-down hippocampal Netrin-1 in the post-weaning period by lentivirus interference alleviated visceral hypersensitivity and anxiety-like behaviors of MS rats in the later phase of life. In addition, deleted in colorectal cancer (DCC), instead of neogenin-1(Neo-1) or uncoordinated (UNC5), was proved to be the specific functional receptor of Netrin-1 in regulating visceral hypersensitivity, whose upregulation may result in the most severe symptoms in the prepubertal period. Furthermore, the activation of the Netrin-1/DCC pathway could enhance long-term potentiation (LTP) in the hippocampus, probably via recruitment of the AMPA receptor subunit GluA1, which finally resulted in the formation of visceral hypersensitivity. These novel findings suggest that long-lasting over-expression of Netrin-1 can mediate visceral hypersensitivity and anxiety disorder from the post-weaning period to adulthood by activating DCC/GluA1 pathway in the hippocampus. Moreover, early intervention of Netrin-1 in the post-weaning period could lead to significant symptom relief afterward, which provides evidence that the Netrin-1/DCC/GluA1 signaling pathway may be a potential therapeutic target for the treatment of visceral hypersensitivity in clinics.

Anxiety, aggression, reward sensitivity, and forebrain dopamine receptor expression in a laboratory rat model of early‐life disadvantage

“…These changes resulting from early‐life adversity likely reflect that the DA system undergoes substantial modifications during early development through adolescence, and thus particularly susceptible to perturbation (Sanchez & Bangasser, 2022). Although the mechanisms underlying the changes we found in D1 and D2 expression after early‐life lead or restricted bedding remain to be elucidated, we conjecture that they may involve changes in Netrin‐1 expression, which is disrupted following maternal separation (Wang et al., 2022) and has repeatedly been implicated in mPFC and NAc DA system maturation (Flores, 2011; Reynolds et al., 2015; Reynolds et al., 2018).…”

Overexpression of EphB2 in the basolateral amygdala is crucial for inducing visceral pain sensitization in rats subjected to water avoidance stress

“…In IBS, chronic abdominal pain is a process associated with induction and maintenance of visceral hypersensitivity. Visceral hypersensitivity persists even though the initial pathogenic factors such as psychological stressors were removed 33 . However, many studies only focused on the stage when chronic pain has been established but not its induction 21 .…”

“…As described previously, total RNA was collected and reverse transcribed into cDNA 33 . Expression levels of target genes were analyzed by qPCR Master Mix (G3326, Wuhan Servicebio Technology, China).…”

“…The VMR to colorectal distension (CRD) was recorded by the abdominal muscle electromyogram (EMG) as previously described. 33 In brief, after anesthetized with intraperitoneal injection of pentobarbital sodium (50 mg/kg), a pair of silver wires were implanted into the left external abdominal oblique muscle. Rats were individually housed for 3 days following surgery.…”

Investigation of the causal association between Parkinson’s disease and autoimmune disorders: a bidirectional Mendelian randomization study

“…It is well-known that deficits in dopamine and 5-HT signaling are implicated in the initiation and progression of PD ( 46 , 47 ), but as for IBS, reduced levels of these neurotransmitters could mitigate pathological symptoms like diarrhea, abdominal pain and discomfort and stabilize intestinal permeability ( 48 – 51 ). Additionally, although decreased netrin-1 concentrations in the brain and gut of PD patients resulted in significant loss of motor function, it provided an obvious alleviation effect on visceral hypersensitivity, a core characteristic in approximately half of patients with IBS ( 52 , 53 ). Thus, future large-scale prospective cohort studies are urgently required to verify this causal relationship.…”