Lymphotoxin ß receptor signaling promotes development of autoimmune pancreatitis.

BACKGROUND & AIMS: Little is known about the pathogenic mechanisms of autoimmune pancreatitis (AIP), an increasingly recognized, immune-mediated form of chronic pancreatitis. Current treatment options are limited and disease relapse is frequent. We investigated factors that contribute to the development of AIP and new therapeutic strategies. METHODS: We used quantitative polymerase chain reaction, immunohistochemical, and enzyme-linked immunosorbent analyses to measure the expression of cytokines and chemokines in tissue and serum samples from patients with and without AIP. We created a mouse model of human AIP by overexpressing lymphotoxin (LT)α and ß specifically in acinar cells (Ela1-LTab mice). RESULTS: Messenger RNA levels of LTα and ß were increased in pancreatic tissues from patients with AIP, compared with controls, and expression of chemokines (CXCL13, CCL19, CCL21, CCL1, and B-cell-activating factor) was increased in pancreatic and serum samples from patients. Up-regulation of these factors was not affected by corticosteroid treatment. Acinar-specific overexpression of LTαß (Ela1-LTαß) in mice led to an autoimmune disorder with various features of AIP. Chronic inflammation developed only in the pancreas but was sufficient to cause systemic autoimmunity. Acinar-specific overexpression of LTαß did not cause autoimmunity in mice without lymphocytes (Ela1-LTab/Rag1(-/-)); moreover, lack of proinflammatory monocytes (Ela1-LTab/Ccr2(-/-)) failed to prevent AIP but prevented early pancreatic tissue damage. Administration of corticosteroids reduced pancreatitis but did not affect production of autoantibodies, such as antipancreatic secretory trypsin inhibitor in Ela1-LTab mice. In contrast, inhibition of LTßR signaling reduced chemokine expression, renal immune-complex deposition, and features of AIP in Ela1-LTab mice. CONCLUSIONS: Overexpression of LTαß specifically in acinar cells of mice causes features of AIP. Reagents that neutralize LTßR ligands might be used to treat patients with AIP.

Circulating lymphotoxin ß receptor and atherosclerosis: observations from the Dallas Heart Study.

OBJECTIVE: Lymphotoxin ß receptor (LTßR), a member of the tumor necrosis factor superfamily, binds ligands expressed by activated lymphocytes. Interruption of LTßR signaling improves autoimmune diseases and alters lipid homeostasis. We assayed circulating LTßR and examined its association with atherosclerosis phenotypes in a population-based sample. METHODS AND RESULTS: Plasma LTßR was measured by ELISA in 3215 subjects enrolled in the Dallas Heart Study. Atherosclerosis was assessed using CT measurements of coronary calcium (CAC) and abdominal MRI measurements of aortic plaque (AP) (n=2252) and aortic wall thickness (AWT) (n=2265). We analyzed associations between LTßR and atherosclerosis using multivariable logistic and linear regression methods. Higher levels of LTßR associated with most traditional cardiovascular risk factors, multiple inflammatory markers, and markers of cardiac injury. Univariable analyses demonstrated significant associations of LTßR with CAC, AP, and AWT (p<0.0001 for each). In multivariable models adjusted for traditional risk factors, the 4th vs. the 1st quartile of LTßR remained associated with prevalent CAC, AP, and increased AWT (all p<0.05). Similar associations were observed when LTßR was modeled as a log-transformed continuous variable. CONCLUSION: LTßR levels are independently associated with atherosclerosis in multiple vascular beds. These findings support further investigation of the lymphotoxin/LTßR pathway in atherosclerosis.

High levels of Lymphotoxin-Beta (LT-Beta) gene expression in rheumatoid arthritis synovium: clinical and cytokine correlations.

Lymphotoxin-Beta (LT-Beta) is implicated in lymphoid follicle development, production of pro-inflammatory cytokines, and can enhance the proliferation of fibroblasts and synoviocytes. The objective of this study was to investigate LT-Beta and LT-BetaReceptor (LT-BetaR) gene expression in RA patient synovium and blood samples compared with control individuals, and correlate with LT-Alpha and TNF-Alpha gene expression and disease parameters. RT-PCR was used to investigate the gene expression of LT-Beta, LT-BetaR, TNF-Alpha and LT-Alpha in the blood and synovium of RA patients and a control group of individuals. LT-Beta gene expression was significantly higher in RA patient synovium compared to control synovium (P = 0.005). There was a significant positive correlation between LT-Beta and LT-Alpha gene expression in both the synovium (P = 0.001) and blood (P = 0.002) of RA patients. LT-Beta gene expression was significantly higher in RA patient synovial samples that were inflamed to a moderately severe degree compared to those inflamed to a minimal degree (P = 0.02). Analysis of clinical variables revealed a significant positive correlation between LT-BetaR gene expression in RA patient synovium and Pain VAS Score (P = 0.01) and also HAQ Score (P = 0.01). Increased LT-Beta gene expression occurs in RA synovium and correlates with the degree of inflammation. LT-Beta may play a role in RA disease pathogenesis by contributing to a more intense inflammatory reaction in the synovium.