title: Reduced Expression of DNA Damage Repair Genes High Mobility Group Box1 and Poly(ADP-ribose) Polymerase1 in Inactive Carriers of Hepatitis B Virus Infection-A Possible Stage of Viral Integration.
abstract: BACKGROUND
  High mobility group box1 (HMGB1) and poly(ADP-ribose) polymerase1 (PARP1) proteins repair cellular DNA damage. Reduced expression of the corresponding genes can lead to an impaired DNA damage repair mechanism. Intracellular replication of hepatitis B virus (HBV) in such conditions can favor the integration of viral DNA into host genome leading to the development of hepatocellular carcinoma (HCC).
  
  
  OBJECTIVE
  This study was performed to assess the expression of HMGB1 and PARP1 mRNAs in conjunction with the estimation of HBV replication intermediate pregenomic RNA (PgRNA) in various phases of HBV infection.
  
  
  METHODS
  Eighty eight patients and 26 voluntary blood donors as controls were included in the study. Patients were grouped in to acute (AHB; n = 15), inactive carriers (IC; n = 36), cirrhosis (Cirr; n = 25) and hepatocellular carcinoma (HCC; n = 12). Serum HBV DNA was quantified by real time polymerase chain reaction (PCR) assay. Expression of HMGB1, PARP1 and PgRNA were evaluated using peripheral blood mononuclear cells (PBMCs) derived RNA by reverse transcription PCR (RT-PCR) and densitometry.
  
  
  RESULTS
  Significant reduction of HMGB1 and PARP1 gene expressions (P < 0.05) were observed in patients than controls with more explicit decline of PARP1 (P = 0.0002). Both genes were significantly downregulated (P < 0.001) in ICs than controls. In ICs, HMGB1 was significantly lowered than cirrhosis (P = 0.002) and HCC (P = 0.0006) while PARP1 declined significantly (P = 0.04) than HCC. Level of PgRNA was comparable in all the disease categories.
  
  
  CONCLUSIONS
  In conclusion, our findings indicate impaired DNA damage repair mechanisms in HBV infected cells of ICs. This, along with low viral load but higher level of PgRNA in this group is suggestive of the diversion of HBV replication pathway that might facilitate viral DNA integration in to host genome. Intrusion of HBV PgRNA reverse transcription in early stage of infection might appear advantageous to thwart the development of HCC.
authors.affiliation: Asian Health Care Foundation, Institute of Basic and Translational Research, 6-3-661, Somajiguda, Hyderabad 500082, India.
authors.forename: Rathindra M
authors.initials: RM
authors.lastname: Mukherjee
authors.affiliation: Asian Institute of Gastroenterology, Somajiguda, Hyderabad, India.
authors.forename: Gelli V
authors.initials: GV
authors.lastname: Shravanti
authors.affiliation: Asian Health Care Foundation, Institute of Basic and Translational Research, 6-3-661, Somajiguda, Hyderabad 500082, India.
authors.forename: Aparna
authors.initials: A
authors.lastname: Jakkampudi
authors.affiliation: Asian Health Care Foundation, Institute of Basic and Translational Research, 6-3-661, Somajiguda, Hyderabad 500082, India.
authors.forename: Ramya
authors.initials: R
authors.lastname: Kota
authors.affiliation: Asian Health Care Foundation, Institute of Basic and Translational Research, 6-3-661, Somajiguda, Hyderabad 500082, India.
authors.forename: Asha L
authors.initials: AL
authors.lastname: Jangala
authors.affiliation: Asian Health Care Foundation, Institute of Basic and Translational Research, 6-3-661, Somajiguda, Hyderabad 500082, India.
authors.forename: Panyala B
authors.initials: PB
authors.lastname: Reddy
authors.affiliation: Asian Institute of Gastroenterology, Somajiguda, Hyderabad, India.
authors.forename: Padaki N
authors.initials: PN
authors.lastname: Rao
authors.affiliation: Asian Institute of Gastroenterology, Somajiguda, Hyderabad, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Gupta
authors.affiliation: Asian Institute of Gastroenterology, Somajiguda, Hyderabad, India.
authors.forename: Duvvuru N
authors.initials: DN
authors.lastname: Reddy
keywords: ADP, adenosine diphosphate; AHB, acute hepatitis B; ALT, alanine transferase; AST, aspartate transferase; BER, base excision repair; CHB, chronic HBV; CIRRH, cirrhosis; CP, Child–Pugh; DEPC, diethyl pyrocarbonate; DTT, dithiothreitol; ELISA, enzyme-linked immunosorbent assay; HAV, hepatitis A virus; HBV, hepatitis B virus; HBX, hepatitis B virus X protein; HBeAg, hepatitis B virus e antigen; HBsAg, hepatitis B virus surface antigen; HCC, hepatocellular carcinoma; HDV, hepatitis delta virus; HEV, hepatitis E virus; HIV, human immunodeficiency virus; HMGB1, high mobility group box1; IC, inactive carriers; IgG, immunoglobulin G; IgM, immunoglobulin M; MuLV-H, moloney murine leukemia virus Rnase H; NER, nucleotide excision repair; PARP1, poly(ADP-ribose) polymerase1; PBMCs, peripheral blood mononuclear cells; PCR, polymerase chain reaction; PgRNA, pregenomic RNA; RT-PCR, reverse transcription PCR; SD, standard deviation; UISs, unique integration sites; cccDNA, covalently closed circular DNA; dNTPs, deoxynucleoside triphosphates; dsDNA, double stranded HBV DNA; gene expression; hepatitis B virus; high mobility group box1; poly(ADP-ribose) polymerase1; pregenomic RNA; rcDNA, relaxed circular DNA