Publications

BACKGROUND & AIMS

Biliary-directed inflammation is an important cause of acute and chronic liver disease. We developed and characterized a transgenic mouse model of immune-mediated hepatobiliary injury.

METHODS

Ovalbumin (OVA)-BIL mice were developed using 3.0 kilobase of the rat apical sodium-dependent bile acid transporter promoter to drive aberrant expression of a membrane form of ovalbumin (OVA) on biliary epithelium. Liver inflammation resulted from adoptive transfer of OVA-specific T cells. Liver immune cells were characterized to determine the mechanism of the response by assessing activation, proliferation, and intracellular cytokine expression.

RESULTS

OVA-BIL transgenic mice were tolerant to OVA, without evidence of liver disease. Adoptive transfer of OVA-specific CD4+ and CD8+ T cells into naïve OVA-BIL mice led to biliary-centered necroinflammatory damage in a dose-dependent manner. This inflammation absolutely required CD8+ T cells and was augmented by CD4+ T cells. Adoptively transferred OVA CD8+ cells homed to and proliferated in the liver but not the spleen. These activated, adoptively transferred cytotoxic T lymphocytes produced elevated levels of tumor necrosis factor alpha and interferon gamma.

CONCLUSIONS

T-cell recognition of antigen aberrantly expressed on bile duct epithelium induced an acute necroinflammatory response specific to the liver, with activation, proliferation, and cytokine production predominantly by the OVA-specific cytotoxic T cells. Thus, OVA BIL represents an antigen-specific animal model of inflammatory bile duct injury.

BACKGROUND

Atrial fibrosis is an important substrate in atrial fibrillation (AF), particularly in the setting of structural heart disease. In a canine model, congestive heart failure (CHF) produces significant atrial fibrosis and the substrate for sustained AF. This atrial remodeling is a potential therapeutic target. The objective of the present study is to evaluate the effects of the antifibrotic drug pirfenidone (PFD) on arrhythmogenic atrial remodeling in a canine CHF model.

METHODS AND RESULTS

We studied 15 canines, divided equally into 3 groups: control, CHF canines not treated with PFD, and CHF canines treated with PFD. CHF was induced by ventricular tachypacing (220 bpm for 3 weeks), and oral PFD was administered for the 3-week pacing period. We performed electrophysiology and AF vulnerability studies, atrial fibrosis measurements, and atrial cytokine expression studies. Only canines in the untreated CHF group developed sustained AF (>30 minutes, 4 of 5 canines; P<0.05). Treatment of CHF canines with PFD resulted in an attenuation of arrhythmogenic left atrial remodeling, with a significant reduction in left atrial conduction heterogeneity index (median [25% to 75% interquartile range] 4.96 [3.53 to 5.64] versus 2.52 [2.11 to 2.82], P<0.01; pacing cycle length 300 ms), left atrial fibrosis (16.0% [13.0% to 17.5%] versus 8.7% [5.7% to 10.6%], P<0.01), and AF duration (1800 [1020 to 1800] seconds versus 6 [5 to 22] seconds, P<0.01). Immunoblotting studies demonstrated the drug's effects on multiple cytokines, including a reduction in transforming growth factor-beta1 expression.

CONCLUSIONS

Treatment of CHF canines with PFD results in significantly reduced arrhythmogenic atrial remodeling and AF vulnerability. Pharmacological therapy targeted at the fibrotic substrate itself may play an important role in the management of AF.

APOBEC3G (A3G) and related deoxycytidine deaminases are potent intrinsic antiretroviral factors. A3G is expressed either as an enzymatically active low-molecular-mass (LMM) form or as an enzymatically inactive high-molecular-mass (HMM) ribonucleoprotein complex. Resting CD4 T cells exclusively express LMM A3G, where it functions as a powerful postentry restriction factor for HIV-1. Activation of CD4 T cells promotes the recruitment of LMM A3G into 5- to 15-MDa HMM complexes whose function is unknown. Using tandem affinity purification techniques coupled with MS, we identified Staufen-containing RNA-transporting granules and Ro ribonucleoprotein complexes as specific components of HMM A3G complexes. Analysis of RNAs in these complexes revealed Alu and small Y RNAs, two of the most prominent nonautonomous mobile genetic elements in human cells. These retroelement RNAs are recruited into Staufen-containing RNA-transporting granules in the presence of A3G. Retrotransposition of Alu and hY RNAs depends on the reverse transcriptase machinery provided by long interspersed nucleotide elements 1 (L1). We now show that A3G greatly inhibits L1-dependent retrotransposition of marked Alu retroelements not by inhibiting L1 function but by sequestering Alu RNAs in cytoplasmic HMM A3G complexes away from the nuclear L1 enzymatic machinery. These findings identify nonautonomous Alu and hY retroelements as natural cellular targets of A3G and highlight how different forms of A3G uniquely protect cells from the threats posed by exogenous retroviruses (LMM A3G) and endogenous retroelements (HMM A3G).