Expression of cyclooxygenase-2 in intestinal goblet cells of pre-diabetic NOD mice

Cox-2 Expressed with Insulin in Pancreatic Beta-Cells, and in the Infiltrated Leukocytes in Inflamed Islets of Diabetic Mice

In the event of the onset of type 1 diabetes (T1D) the circulating autoantibodies against the beta-cell of the pancreas are attacked by macrophages and autoreactive lymphocytes under the influence of different cytokines. Eventually, beta-cells are destroyed through apoptosis, or natural killer cells, or a scavenger process. Cyclooxygenase (COX)-2 is constitutively expressed in beta-cells, the possible role in insulin secretion and insulitis has been suggested. However, COX-2 with lymphocytes and other infiltrated leukocytes on diabetogenesis remains largely elusive. We injected diabetic lymphocytes of non-obese diabetic (NOD) mice to NOD/SCID mice for adoptive transfer. The diabetogenesis of adoptive transferred NOD/SCID mice was tested with supplements of COX-2 inhibitor or the substrate, arachidonic acid, in the diets under placebo control. The tissues of intestine and pancreas of BALB/c, NOD and NOD/SCID mice were immunohistochemically analyzed. COX-2 and insulin were revealed in the vesicles of beta-cells in intact islets of BALB/c mice. The lymphocyte tracking of the transferred lymphocytes and COX-2 expression in beta-cells and emerged leukocytes showed that celecoxib, or the substrate did not change the pattern of lymphocyte accumulation in the pancreas compared to placebo, even though the development of severe diabetes was slightly different. COX-2 was only expressed in macrophages, rather than infiltrated lymphocytes. Morphology showed that the emerged lymphocytes migrated from outside islets indicating that the disructive impact of COX-2 on beta cells is probably limited. The enhanced expression of COX-2 and insulin in random beta-cells is likely associated with the genesis of diabetes, a possible mechanism to increase or extend insulin secretion in the late period of insulitis.

Lactobacillus johnsonii N6.2 mitigates the development of type 1 diabetes in BB-DP rats

Background

The intestinal epithelium is a barrier that composes one of the most immunologically active surfaces of the body due to constant exposure to microorganisms as well as an infinite diversity of food antigens. Disruption of intestinal barrier function and aberrant mucosal immune activation have been implicated in a variety of diseases within and outside of the gastrointestinal tract. With this model in mind, recent studies have shown a link between diet, composition of intestinal microbiota, and type 1 diabetes pathogenesis. In the BioBreeding rat model of type 1 diabetes, comparison of the intestinal microbial composition of diabetes prone and diabetes resistant animals found Lactobacillus species were negatively correlated with type 1 diabetes development. Two species, Lactobacillus johnsonii and L. reuteri, were isolated from diabetes resistant rats. In this study diabetes prone rats were administered pure cultures of L. johnsonii or L. reuteri isolated from diabetes resistant rats to determine the effect on type 1 diabetes development.

Methodology/Principal

Findings Results Rats administered L. johnsonii, but not L. reuteri, post-weaning developed type 1 diabetes at a protracted rate. Analysis of the intestinal ileum showed administration of L. johnsonii induced changes in the native microbiota, host mucosal proteins, and host oxidative stress response. A decreased oxidative intestinal environment was evidenced by decreased expression of several oxidative response proteins in the intestinal mucosa (Gpx1, GR, Cat). In L. johnsonii fed animals low levels of the pro-inflammatory cytokine IFNγ were correlated with low levels of iNOS and high levels of Cox2. The administration of L. johnsonii also resulted in higher levels of the tight junction protein claudin.

Conclusions

It was determined that the administration of L. johnsonii isolated from BioBreeding diabetes resistant rats delays or inhibits the onset of type 1 diabetes in BioBreeding diabetes prone rats. Taken collectively, these data suggest that the gut and the gut microbiota are potential agents of influence in type 1 diabetes development. These data also support therapeutic efforts that seek to modify gut microbiota as a means to modulate development of this disorder.

Altered monocyte cyclo-oxygenase response in non-obese diabetic mice

Monocytes infiltrate islets in non-obese diabetic (NOD) mice. Activated monocyte/macrophages express cyclo-oxygenase-2 (COX-2) promoting prostaglandin-E(2) (PGE(2)) secretion, while COX-1 expression is constitutive. We investigated in female NOD mice: (i) natural history of monocyte COX expression basally and following lipopolysaccharide (LPS) stimulation; (ii) impact of COX-2 specific inhibitor (Vioxx) on PGE(2), insulitis and diabetes. CD11b(+) monocytes were analysed for COX mRNA expression from NOD (n = 48) and C57BL/6 control (n = 18) mice. NOD mice were treated with either Vioxx (total dose 80 mg/kg) (n = 29) or methylcellulose as control (n = 29) administered by gavage at 4 weeks until diabetes developed or age 30 weeks. In all groups, basal monocyte COX mRNA and PGE(2) secretion were normal, while following LPS, after 5 weeks of age monocyte/macrophage COX-1 mRNA decreased (P < 0.01) and COX-2 mRNA increased (P < 0.01). However, diabetic NOD mice had reduced COX mRNA response (P = 0.03). Vioxx administration influenced neither PGE(2), insulitis nor diabetes. We demonstrate an isoform switch in monocyte/macrophage COX mRNA expression following LPS, which is altered in diabetic NOD mice as in human diabetes. However, Vioxx failed to affect insulitis or diabetes. We conclude that monocyte responses are altered in diabetic NOD mice but COX-2 expression is unlikely to be critical to disease risk.

Is COX-2 a perpetrator or a protector? Selective COX-2 inhibitors remain controversial

COX-2(cyclooxygenase-2) has sparked a surge in pharmaceutical interest since its discovery at the beginning of the 1990s. Several COX-2 selective inhibitors that avoid gastrointestinal side effects have been successfully launched into the market in recent years. The first selective COX-2 inhibitor, celecoxib, entered the market in December 1998 [corrected] However, there are a few organs that physiologically and functionally express COX-2, particularly the glomeruli of the kidney and the cortex of the brain. Inhibition of COX-2 expression in these organs possibly causes heart attack and stroke in long-term COX-2 inhibitor users. Recently, a USA Food and Drug Agency (FDA) advisory panel re-evaluated COX-2 inhibitors and unanimously concluded that the entire class of COX-2 inhibitors increase the risk of cardiovascular problems. Thus the use of COX-2 inhibitors is still controversial, and there is a challenge for not only pharmacologists, but also the pharmaceutical industry, to develop improved painkilling and anti-inflammatory drugs. This may involve exploring a new generation of COX-2 inhibitors with different inhibitory mechanisms through computer-aided design, screening different sources of inhibitors with lower selectivity, or seeking completely new targets. Synthetic COX-2 inhibitors have high selectivity and the advantage of irreversible inhibition, whereas naturally derived COX-2 inhibitors have lower selectivity and fewer side effects, with the medical effects in general not being as striking as those achieved using synthetic inhibitors. This review discusses the mechanism of COX-2 inhibitor therapy and a possible new way of exploration in the development of anti-inflammatory, analgetic, and antipyretic drugs.

Changes in intestinal morphology and permeability in the biobreeding rat before the onset of type 1 diabetes

OBJECTIVE

Type 1 diabetes is an autoimmune disorder that occurs in genetically susceptible individuals. It has been hypothesized that the disease could be triggered by environmental agents that gain entry into the body through small intestinal absorption. Increased intestinal permeability has been reported both in spontaneous animal models of type 1 diabetes and human type 1 diabetes. In these studies, we examined both the physical and functional permeability characteristics of the small intestine in diabetes-prone and control rats.

METHODS

In a series of studies, BioBreeding diabetes-prone(n = 31), BioBreeding diabetes-resistant (n = 20) and control Wistar (n = 25) rats were examined at intervals from 21 to 125 days of age.

RESULTS

The percentage of goblet cells and the mucosal crypt depth were significantly greater in BioBreeding diabetes-prone than BioBreeding diabetes-resistant rats (P < 0.001 and P = 0.01, respectively). BioBreeding diabetes-prone and BioBreeding diabetes-resistant rats expressed less of the tight junction protein claudin (P < 0.05) and exhibited greater intestinal permeability (P < 0.001) than did Wistar rats. Intestinal permeability measured both in vivo and ex vivo decreased in all rat strains as age increased (P < 0.001).

CONCLUSIONS

In a genetically susceptible rodent model of diabetes, early increased intestinal permeability might allow unregulated passage of environmental antigens that could potentially trigger the autoimmune response leading to type 1 diabetes.