Complement and Alcoholic Liver Disease: Role of C1q in the Pathogenesis of Ethanol-Induced Liver Injury in Mice

doi:10.1053/j.gastro.2010.04.041

Gastroenterology

Volume 139, Issue 2, August 2010, Pages 664-674.e1

https://doi.org/10.1053/j.gastro.2010.04.041 Get rights and content

Background & Aims

Complement is involved in the development of alcoholic liver disease in mice; however, the mechanisms for complement activation during ethanol exposure have not been identified. C1q, the recognition subunit of the first complement component, binds to apoptotic cells, thereby activating the classical complement pathway. Because ethanol exposure increases hepatocellular apoptosis, we hypothesized that ethanol-induced apoptosis would lead to activation of complement via the classical pathway.

Methods

Wild-type and C1qa^−/− mice were allowed free access to ethanol-containing diets or pair-fed control diets for 4 or 25 days.

Results

Ethanol feeding for 4 days increased apoptosis of Kupffer cells in both wild-type and C1qa^−/− mice. Ethanol-induced deposition of C1q and C3b/iC3b/C3c was colocalized with apoptotic Kupffer cells in wild-type, but not C1qa^−/−, mice. Furthermore, ethanol-induced increases in tumor necrosis factor–α and interleukin-6 expression at this early time point were suppressed in C1q-deficient mice. Chronic ethanol feeding (25 days) increased steatosis, hepatocyte apoptosis, and activity of serum alanine and aspartate aminotransferases in wild-type mice. These markers of hepatocyte injury were attenuated in C1qa^−/− mice. In contrast, chronic ethanol (25 days)-induced increases in cytochrome P450 2E1 expression and oxidative stress did not differ between wild-type and C1qa^−/− mice.

Conclusions

For the first time, these data indicate that ethanol activates the classical complement pathway via C1q binding to apoptotic cells in the liver and that C1q contributes to the pathogenesis of ethanol-induced liver injury.

Section snippets

Materials

Female C57BL/6 mice were purchased from Jackson Laboratory (Bar Harbor, ME). C1qa^−/− mice were originally developed by Botto et al¹⁷ and back-crossed on a C57BL/6 background.¹⁸ A breeding pair provided to us by Dr Michael Carroll at Center for Blood Research, Harvard University, Boston, was then used to establish a breeding colony at the Cleveland Clinic. Lieber-DeCarli high-fat ethanol liquid diet was purchased from Dyets (Bethlehem, PA). Antibodies were purchased from the following sources:

Hepatic C1q and C3b Deposition in Mice After Short-term Ethanol

Complement activation contributes to the progression of ethanol-induced liver injury5, 6, 7; however, the specific complement activation pathways involved in the response to ethanol are not known.6, 7 In wild-type mice, ethanol feeding for 4 days increases the deposition of C3b/iC3b/C3c (abbreviated here to C3b for convenience) in hepatic sinusoids.⁶ If the classical pathway of complement activation contributes to ethanol-induced complement activation, then C1q protein would also deposit in the

Discussion

Activation of complement is required for development of ethanol-induced liver injury in mice5, 7; however, the specific pathways by which ethanol exposure activates complement have not been identified. Here we have identified for the first time an essential role of C1q in ethanol-induced complement activation after short-term/low-dose ethanol (4 days/11%) and chronic/high-dose ethanol (25 days/32%). Importantly, in the absence of C1q, mice were protected from hepatic pathology associated with

Acknowledgments

The authors thank Drs Marino Botto and Michael Carroll for sharing the C1qa^−/− mice, Emmanuelle Ogier and Brian T. Pratt for the outstanding technical assistance, and Dr Michele T. Pritchard for critical discussions of the data and manuscript.

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: Conflicts of interest The authors disclose no conflicts.

: Funding This work was supported in part by RO1AA016399 to L.E.N. and 1 F31 AA016434 to J.I.C.

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Basic—Liver, Pancreas, and Biliary TractComplement and Alcoholic Liver Disease: Role of C1q in the Pathogenesis of Ethanol-Induced Liver Injury in Mice

Background & Aims

Methods

Results

Conclusions

Section snippets

Materials

Hepatic C1q and C3b Deposition in Mice After Short-term Ethanol

Discussion

Acknowledgments

Free Radic Biol Med

Mol Immunol

Clin Immunol

Gastroenterology

J Biol Chem

Mol Immunol

Mol Immunol

Immunol Lett

Immunobiology

Free Radic Biol Med

Hepatol Res

J Biol Chem

Alcohol

J Hepatol

Cell

Gastroenterology

Immune mechanisms in alcoholic liver disease

Genes Nutr

An early complement-dependent and TLR-4-independent phase in the pathogenesis of ethanol-induced liver injury in mice

Hepatology

Complement C3 contributes to ethanol-induced liver steatosis in mice

Ann Med

C1q binds phosphatidylserine and likely acts as a multiligand-bridging molecule in apoptotic cell recognition

J Immunol

Basic—Liver, Pancreas, and Biliary Tract
Complement and Alcoholic Liver Disease: Role of C1q in the Pathogenesis of Ethanol-Induced Liver Injury in Mice