Chronic stress is commonly associated with enhanced abdominal pain (visceral hyperalgesia) and altered bowel habits in humans with Irritable Bowel Syndrome (IBS) and validated animal models via activation of the HPA-axis and the glucocorticoid receptor (GR) transcription factor. The cellular and molecular mechanisms underlying chronic stressed-associated visceral hyperalgesia are poorly understood; however, emerging evidence indicates that the visceral hyperalgesia is linked to decreased expression of colon epithelial cell tight junction proteins and increased paracellular permeability. Our lab and others have reported a potentially significant role for epigenetic mechanisms in nociceptive neural pathways in chronic stress-induced visceral hyperalgesia. It is unknown whether epigenetic mechanisms are directly involved in the decreased expression in intestinal epithelial tight junction proteins, increased paracellular permeability and visceral hyperalgesia. In this proposal, we provide compelling preliminary data supporting the novel hypothesis that methylation of repressive histone H3K9 plays a pivotal role in chronic stress- and pro-inflammatory cytokine-mediated visceral hyperalgesia via down-regulation in colon epithelial tight junction proteins and increased paracellular permeability using two validated rat models (males and females) and patients with diarrhea-prone IBS (males and females), differentiated human Caco-2 cells, human-derived colonoids and human-derived colon epithelial cell monolayers. We will examine the following vertically-integrated specific aims to confirm the role of H3K9me2/me3 in the pathophysiology of chronic stress-associated visceral hyperalgesia:
Specific Aim 1 : Test the global hypothesis that methylation of the repressive histone H3K9 plays a key role in chronic stress- induced intestinal barrier dysfunction and visceral hyperalgesia using two validated male animal models;
Specific Aim 2 : Examine how H3K9 methylation regulates intestinal epithelial tight junction gene transcription and protein expression, paracellular permeability and visceral hyperalgesia in response to chronic stress, corticosterone and pro-inflammatory cytokines;
and Specific Aim 3 : Assess the translatability of the animal studies to the human and potential differences based on biological sex. The application is highly significant because of the clinical importance of chronic stress to enhance visceral pain and the novel global hypothesis, innovative because of the use of state-of-art methods to study the global hypothesis in a systematic manner and high impact because of the potential to influence current thinking in the field.
The goal of this proposal is confirm the preliminary observation that the repressive histone marks H3K9me2 and H3K9me3 play a pivotal role in chronic stress- and pro-inflammatory cytokine-mediated enhanced abdominal pain (visceral hyperalgesia) via down-regulation of intestinal epithelial tight junction proteins and concomitant increase in paracellular permeability.
