Gadolinium Chloride Restores the Function of the Gap Junctional Intercellular Communication between Hepatocytes in a Liver Injury

Abstract

Background: Gadolinium chloride (GdCl3) has been reported to attenuate liver injury caused by a variety of toxicants. Gap junctional intercellular communication (GJIC) is thought to be essential in controlling liver homeostasis and pathology. Here we evaluate the effects of GdCl3 on functional GJIC and connexin expression in mouse models and primary hepatocytes. Methods: Mice were administered GdCl3 intraperitoneally the day before a carbon tetrachloride (CCl4) injection or bile duct ligation (BDL) operation. Primary hepatocytes were treated with CCl4 or lipopolysaccharides (LPS), with or without GdCl3. A scrape loading/dye transfer assay was performed to assess the GJIC function. The expression of connexins was examined by real-time reverse transcription polymerase chain reaction (RT-PCR), western blot and immunofluorescent staining. Results: CCl4 treatment or the BDL operation led to the dysfunction of GJIC and a down-regulation of Cx32 and Cx26 in injured liver. GdCl3 administration restored GJIC function between hepatocytes by facilitating the transfer of fluorescent dye from one cell into adjacent cells via GJIC, and markedly prevented the decrease of Cx32 and Cx26 in injured liver. In primary hepatocytes, CCl4 or LPS treatment induced an obvious decline of Cx32 and Cx26, whereas GdCl3 pretreatment prevented the down-regulation of connexins. In vivo GdCl3 protected hepatocytes and attenuated the liver inflammation and fibrosis in liver injury mouse models. Conclusion: GdCl3 administration protects functional GJIC between hepatocytes, and prevents the decrease of connexin proteins at mRNA and protein levels during liver injury, leading to the alleviation of chronic liver injury.

Targeting gap junctional intercellular communication by hepatocarcinogenic compounds

“…These findings are in agreement with previous in vivo studies in rats, where lower protein levels, but a rise in mRNA was seen, albeit for Cx32 (Nakata et al 1996;Miyashita et al 1991;Cowles et al 2007). However, Yang et al (2019) recently noted a fall in Cx32 and Cx26 mRNA levels upon CCl4 administration. Despite this contradiction with earlier studies, the previously reported functional inhibition of GJIC was observed (Yang et al 2019;Nakata et al 1996).…”

“…However, Yang et al (2019) recently noted a fall in Cx32 and Cx26 mRNA levels upon CCl4 administration. Despite this contradiction with earlier studies, the previously reported functional inhibition of GJIC was observed (Yang et al 2019;Nakata et al 1996). This inhibitory effect of CCl4 is associated with cytotoxicity (Cowles et al 2007), primarily mediated by oxidative and lipid peroxidative damage indirectly triggering genotoxicity (Eastmond 2008).…”

“…Given their critical role in maintaining homeostasis, it is not surprising that gap junctions are frequently involved in pathological conditions (Yamasaki et al 1999). A wide spectrum of alterations were found in connexin expression and gap junction functionality in liver diseases, including cholestasis (Fallon et al 1995), non-alcoholic steatohepatitis (Luther et al 2018), fibrosis (Fischer et al 2005), cirrhosis (Yang et al 2019) and liver cancer (Xiang et al 2019).…”

“…Lipopolysaccharide (LPS) is an endotoxin located in the outer membrane of Gram-negative bacteria that initiates acute inflammation in animals. A number of studies reported marked reduction of Cx32 production in response to administration of LPS in vitro (Yang et al 2019) and in vivo in both mice (Temme et al 2000) and rats (Correa et al 2004;Gingalewski et al 1996;Gonzalez et al 2002). This reduction may be attributed to enhanced protein degradation and inhibition of Cx32 mRNA expression (Yang et al 2019).…”

“…A number of studies reported marked reduction of Cx32 production in response to administration of LPS in vitro (Yang et al 2019) and in vivo in both mice (Temme et al 2000) and rats (Correa et al 2004;Gingalewski et al 1996;Gonzalez et al 2002). This reduction may be attributed to enhanced protein degradation and inhibition of Cx32 mRNA expression (Yang et al 2019). This is associated with lowered mRNA stability induced by alterations in posttranscriptional modifications of Cx32 gene 14 expression, such as shortening of the poly(A)tail (Gingalewski et al 1996;Theodorakis and De Maio 1999).…”