BACKGROUND: Alcoholic liver disease is manifested by the presence of fatty liver, primarily due to accumulation of hepatocellular lipid droplets (LDs). The presence of membrane-trafficking proteins (e.g., Rab GTPases) with LDs indicates that LDs may be involved in trafficking pathways known to be altered in ethanol (EtOH) damaged hepatocytes. As these Rab GTPases are crucial regulators of protein trafficking, we examined the effect EtOH administration has on hepatic Rab protein content and association with LDs. METHODS: Male Wistar rats were pair-fed Lieber-DeCarli diets for 5 to 8 weeks. Whole liver and isolated LD fractions were analyzed. Identification of LDs and associated Rab proteins was performed in frozen liver or paraffin-embedded sections followed by immunohistochemical analysis. RESULTS: Lipid accumulation was characterized by larger LD vacuoles and increased total triglyceride content in EtOH-fed rats. Rabs 1, 2, 3d, 5, 7, and 18 were analyzed in postnuclear supernatant (PNS) as well as LDs. All of the Rabs were found in the PNS, and Rabs 1, 2, 5, and 7 did not show alcohol-altered content, while Rab 3d content was reduced by over 80%, and Rab 18 also showed EtOH-induced reduction in content. Rab 3d was not found to associate with LDs, while all other Rabs were found in the LD fractions, and several showed an EtOH-related decrease (Rabs 2, 5, 7, 18). Immunohistochemical analysis revealed the enhanced content of a LD-associated protein, perilipin 2 (PLIN2) that was paralleled with an associated decrease of Rab 18 in EtOH-fed rat sections. CONCLUSIONS: Chronic EtOH feeding was associated with increased PLIN2 and altered Rab GTPase content in enriched LD fractions. Although mechanisms driving these changes are not established, further studies on intracellular protein trafficking and LD biology after alcohol administration will likely contribute to our understanding of fatty liver disease.
BACKGROUND:Alcoholic liver disease is manifested by the presence of fatty liver, primarily due to accumulation of hepatocellular lipid droplets (LDs). The presence of membrane-trafficking proteins (e.g., Rab GTPases) with LDs indicates that LDs may be involved in trafficking pathways known to be altered in ethanol (EtOH) damaged hepatocytes. As these Rab GTPases are crucial regulators of protein trafficking, we examined the effect EtOH administration has on hepatic Rab protein content and association with LDs. METHODS: Male Wistar rats were pair-fed Lieber-DeCarli diets for 5 to 8 weeks. Whole liver and isolated LD fractions were analyzed. Identification of LDs and associated Rab proteins was performed in frozen liver or paraffin-embedded sections followed by immunohistochemical analysis. RESULTS:Lipid accumulation was characterized by larger LD vacuoles and increased total triglyceride content in EtOH-fed rats. Rabs 1, 2, 3d, 5, 7, and 18 were analyzed in postnuclear supernatant (PNS) as well as LDs. All of the Rabs were found in the PNS, and Rabs 1, 2, 5, and 7 did not show alcohol-altered content, while Rab 3d content was reduced by over 80%, and Rab 18 also showed EtOH-induced reduction in content. Rab 3d was not found to associate with LDs, while all other Rabs were found in the LD fractions, and several showed an EtOH-related decrease (Rabs 2, 5, 7, 18). Immunohistochemical analysis revealed the enhanced content of a LD-associated protein, perilipin 2 (PLIN2) that was paralleled with an associated decrease of Rab 18 in EtOH-fed rat sections. CONCLUSIONS: Chronic EtOH feeding was associated with increased PLIN2 and altered Rab GTPase content in enriched LD fractions. Although mechanisms driving these changes are not established, further studies on intracellular protein trafficking and LD biology after alcohol administration will likely contribute to our understanding of fatty liver disease.
Authors: Laura L Listenberger; Xianlin Han; Sarah E Lewis; Sylvaine Cases; Robert V Farese; Daniel S Ory; Jean E Schaffer Journal: Proc Natl Acad Sci U S A Date: 2003-03-10 Impact factor: 11.205
Authors: Yumi Imai; Gladys M Varela; Malaka B Jackson; Mark J Graham; Rosanne M Crooke; Rexford S Ahima Journal: Gastroenterology Date: 2007-02-23 Impact factor: 22.682
Authors: Sathish Kumar Natarajan; Karuna Rasineni; Murali Ganesan; Dan Feng; Benita L McVicker; Mark A McNiven; Natalia A Osna; Justin L Mott; Carol A Casey; Kusum K Kharbanda Journal: Curr Mol Pharmacol Date: 2017 Impact factor: 3.339
Authors: Paul G Thomes; Karuna Rasineni; Li Yang; Terrence M Donohue; Jacy L Kubik; Mark A McNiven; Carol A Casey Journal: Am J Physiol Gastrointest Liver Physiol Date: 2019-02-04 Impact factor: 4.052
Authors: Manuela G Neuman; Helmut K Seitz; Pamela L Tuma; Natalia A Osna; Carol A Casey; Kusum K Kharbanda; Lawrence B Cohen; Steve D H Malnick; Raghabendra Adhikari; Ramyajit Mitra; Raghubendra Singh Dagur; Murali Ganesan; Chava Srinivas; Arumugam Madan Kumar; Moses New-Aaron; Larisa Poluektova; Paul G Thomes; Karuna Rasineni; Mihai Opris; Rolf Teschke Journal: Exp Mol Pathol Date: 2022-02-19 Impact factor: 4.401
Authors: Micah B Schott; Karuna Rasineni; Shaun G Weller; Ryan J Schulze; Arthur C Sletten; Carol A Casey; Mark A McNiven Journal: J Biol Chem Date: 2017-05-17 Impact factor: 5.157
Authors: Jennifer L Groebner; Marlene T Girón-Bravo; Mia L Rothberg; Raghabendra Adhikari; Dean J Tuma; Pamela L Tuma Journal: Am J Physiol Gastrointest Liver Physiol Date: 2019-08-02 Impact factor: 4.052