Membrane potential differences and GABA_A receptor expression in hepatic tumor and non-tumor stem cells

Abstract

The ability to differentiate tumor initiating stem cells (TISCs) from healthy, normal stem cells (NSCs) could have important diagnostic and therapeutic implications for patients with hepatocellular carcinoma (HCC). The aim of this study was to document and compare cell membrane potentials (PDs) and GABAA receptor subunit expression in hepatic TISCs and NSCs. PD values were determined in CD133(+) Huh-7 TISCs and CD133(+) WBF344 NSCs by single channel microelectrode impalement. GABAA receptor subunit expression was documented using immunohistochemistry (IH) in both cell lines as well as surgically resected HCC and healthy liver tissues. TISCs were significantly depolarized compared with NSCs (-4.0 ± 1.8 versus -11.0 ± 2.4 mV, respectively; p < 0.05). GABAA α6 subunit expression was either absent or markedly attenuated, while γ3 subunit expression was abundant in TISCs and HCC compared with NSCs and healthy liver tissues. Exposure to the GABAA receptor agonist muscimol caused hyperpolarization of TISCs (Δ -4.4 ± 1.1) but depolarization of NSCs (Δ + 5.2 ± 2.3) and attenuation of TISC proliferative activity. We conclude that TISCs and NSCs have significantly different cell membrane potentials and these differences are associated with differences in GABAA receptor subunit expression.

Hepatitis B Virus Infection of Normal Hepatic Stem/Progenitor Cells

“…Malignant or cancer stem cells have been previously documented to have depolarized cell membrane potentials, increased proliferative activity and high telomerase levels. 8,14,15 In the present study, none of these features developed in HBV-infected NSCs. Future studies in which NSCs are cultured for periods beyond 30 days are required to more definitively determine whether HBV infection of NSCs ultimately results in the acquisition of these features and/or their predisposition to malignant transformation.…”

“…Changes in cell membrane PDs and in particular, a depolarized state is thought to play an important role in the malignant transformation of non-malignant cells including stem/progenitor cells. 8 In the present study, NSC PDs depolarized (became less negative) following exposure to HBV however, the depolarized state was transient with PD values returning to baseline by day 5 of infection ( Figure 5).…”

“…NSCs were isolated from healthy human liver tissues adjacent to metastatic lesions or benign hepatic tumors in HBsAg negative adult patients undergoing surgical resections for their tumors. Magnetic bead separations based on positive EpCAM expression and characterization of these cells as somatic stem/progenitor cells were carried out as described by Neurauter et al and modified by Bautista et al 8,9 Briefly, liver tissues were dissected and digested in 1 mg/ml of type 4 collagenase (Sigma-Aldrich, Oakville, Ont, CAN) solution at 37 C for 15-30 min. Contaminated red blood cells were lysed with ammonium chloride solution (STEM-CELL Technologies, Miltenyi Biotec, San Diego, CA, USA) on ice for 5 min.…”

An obesogenic feedforward loop involving PPARγ, acyl-CoA binding protein and GABAA receptor

“…Altogether, existing evidence suggests that, in mice, ACBP is embedded in a circuit, where starvation stimulates autophagy, thereby causing ACBP release from cells. Secreted ACBP acts on gamma-aminobutyric acid A receptors (GABA A R) expressed on multiple cell types outside of the central nervous system (e.g., cholangiocytes, hepatocytes, and macrophages) [ 17 – 19 ] to cause a transient decrease in glycemia and the consequent activation of orexigenic circuitries [ 9 – 11 ], thus stimulating food intake and closing a homeostatic feedback loop or “hunger reflex” [ 20 ].…”

Distinct diagnostic and prognostic values of γ‑aminobutyric acid type A receptor family genes in patients with colon adenocarcinoma

“…Therefore, GABRA4 might serve a role in COAD, which requires further study. Bautista et al (31) observed that the expression levels of GABRA6 in tumor initiating stem cells (TISCS) and hepatocellular carcinoma (HCC) were reduced, whereas the expression levels of GABRG3 were abundant in TISCS and limited in HCC. A previous study showed that the specific activation of GABA A receptor decreased cell activity, induced apoptosis and inhibited the growth and survival signal pathway of neuroblastoma cells (32).…”