Hypoxia-inducible factor/MAZ-dependent induction of caveolin-1 regulates colon permeability through suppression of occludin, leading to hypoxia-induced inflammation

The molecular mechanism and effect of cannabinoid-2 receptor agonist on the blood-spinal cord barrier permeability induced by ischemia-reperfusion injury

Previous studies have shown that modulation of the receptor-mediated endocannabinoid system during ischemia injury can induce potent neuroprotective effects. However, little is known about whether cannabinoid-2 (CB2) receptor agonist would produce a protective effect on blood-spinal cord barrier (BSCB) during ischemia. Using an in vivo transient spinal cord ischemia model in rats, JWH-015 (1mg/kg, i.p.), a CB2 receptor selective agonist, or vehicles were injected 20 min before ischemia. The effects of JWH-015 on BSCB permeability, the major structural protein for the formation of caveolae, caveolin-1 (cav-1), tight junction (TJ) protein Occludin and zona occludens protein-1 (ZO-1) were examined at day 1, day 3 and day 7 of reperfusion after transient spinal cord ischemia in rats. Here we demonstrated that JWH-015 significantly down-regulated the expression of cav-1, up-regulated the expression of TJ proteins, and then decreased the permeability of BSCB compared with control group. In addition, using an in vitro BBB model, oxygen glucose deprivation (OGD) was applied to simulate spinal cord ischemia in vitro in Human brain microvascular endothelial cells (HBMECs). JWH-015 greatly increased the transepithelial electrical resistance (TEER) and changed the distribution of ZO-1 and Occludin. Moreover, JWH-015 induced the expression of p-PKB and p-FoxO1 protein and decreased the expression of cav-1, which were greatly reversed by ROS inhibitor or PI3K inhibitor. Taken together, all of these results suggested that JWH-015 might regulate the BSCB permeability and this effect could be related to paracellular and transcellular pathway. And pharmacological CB2R ligands offer a new strategy for BSCB protection during ischemic injury.

The role of hypoxia in intestinal inflammation

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory disease of the intestine. IBD is a multifactorial disorder, and IBD-associated genes are critical in innate immune response, inflammatory response, autophagy, and epithelial barrier integrity. Moreover, epithelial oxygen tension plays a critical role in intestinal inflammation and resolution in IBD. The intestines have a dynamic and rapid fluctuation in cellular oxygen tension, which is dysregulated in IBD. Intestinal epithelial cells have a steep oxygen gradient where the tips of the villi are hypoxic and the oxygenation increases at the base of the villi. IBD results in heightened hypoxia throughout the mucosa. Hypoxia signals through a well-conserved family of transcription factors, where hypoxia-inducible factor (HIF)-1α and HIF-2α are essential in maintaining intestinal homeostasis. In inflamed mucosa, HIF-1α increases barrier protective genes, elicits protective innate immune responses, and activates an antimicrobial response through the increase in β-defensins. HIF-2α is essential in maintaining an epithelial-elicited inflammatory response and the regenerative and proliferative capacity of the intestine following an acute injury. HIF-1α activation in colitis leads to a protective response, whereas chronic activation of HIF-2α increases the pro-inflammatory response, intestinal injury, and cancer. In this mini-review, we detail the role of HIF-1α and HIF-2α in intestinal inflammation and injury and therapeutic implications of targeting HIF signaling in IBD.

Role of Intestinal HIF-2α in Health and Disease

The intestine is supported by a complex vascular system that undergoes dynamic and transient daily shifts in blood perfusion, depending on the metabolic state. Moreover, the intestinal villi have a steep oxygen gradient from the hypoxic epithelium adjacent to the anoxic lumen to the relative higher tissue oxygenation at the base of villi. Due to the daily changes in tissue oxygen levels in the intestine, the hypoxic transcription factors hypoxia-inducible factor (HIF)-1α and HIF-2α are essential in maintaining intestinal homeostasis. HIF-2α is essential in maintaining proper micronutrient balance, the inflammatory response, and the regenerative and proliferative capacity of the intestine following an acute injury. However, chronic activation of HIF-2α leads to enhanced proinflammatory response, intestinal injury, and colorectal cancer. In this review, we detail the major mechanisms by which HIF-2α contributes to health and disease of the intestine and the therapeutic implications of targeting HIF-2α in intestinal diseases.

Alterations of the apical junctional complex and actin cytoskeleton and their role in colorectal cancer progression

Colorectal cancer represents the fourth highest mortality rate among cancer types worldwide. An understanding of the molecular mechanisms that regulate their progression can prevents or reduces mortality due to this disease. Epithelial cells present an apical junctional complex connected to the actin cytoskeleton, which maintains the dynamic properties of this complex, tissue architecture and cell homeostasis. Several studies have indicated that apical junctional complex alterations and actin cytoskeleton disorganization play a critical role in epithelial cancer progression. However, few studies have examined the existence of an interrelation between these 2 components, particularly in colorectal cancer. This review discusses the recent progress toward elucidating the role of alterations of apical junctional complex constituents and of modifications of actin cytoskeleton organization and discusses how these events are interlinked to modulate cellular responses related to colorectal cancer progression toward successful metastasis.