Elevated mitochondrial activity distinguishes fibrogenic hepatic stellate cells and sensitizes for selective inhibition by mitotropic doxorubicin

Abstract

Activation of hepatic stellate cells (HSCs) is an integral component of the wound‐healing process in liver injury/inflammation. However, uncontrolled activation of HSCs leads to constant secretion of collagen‐rich extracellular matrix (ECM) proteins, resulting in liver fibrosis. The enhanced ECM synthesis/secretion demands an uninterrupted supply of intracellular energy; however, there is a paucity of data on the bioenergetics, particularly the mitochondrial (mito) metabolism of fibrogenic HSCs. Here, using human and rat HSCs in vitro, we show that the mito‐respiration, mito‐membrane potential (Δψm) and cellular ‘bioenergetic signature’ distinguish fibrogenic HSCs from normal, less‐active HSCs. Ex vivo, HSCs from mouse and rat models of liver fibrosis further confirmed the altered ‘bioenergetic signature’ of fibrogenic HSCs. Importantly, the distinctive elevation in mito‐Δψm sensitized fibrogenic HSCs for selective inhibition by mitotropic doxorubicin while normal, less‐active HSCs and healthy human primary hepatocytes remained minimally affected if not, unaffected. Thus, the increased mito‐Δψm may provide an opportunity to selectively target fibrogenic HSCs in liver fibrosis.

Metabolic Hallmarks of Hepatic Stellate Cells in Liver Fibrosis

“…In addition, glutamine supports the respiration of activated HSCs [107]. Indeed, HSC activation leads to enhanced oxidative phosphorylation (OXPHOS) [108], a general feature of cells undergoing activation [109]. Inhibition of the Hh pathway with forskolin significantly reduced fibrosis development, oxidative stress, and inflammation in CCl 4 -treated rats [110].…”

“…As mentioned above, activated HSCs exhibit enhanced OXPHOS phenotype [108], which is typically associated with increased production of ROS in mitochondria [109]. Unfortunately, there is no data showing how enhanced ROS production from various sources (at various sites within HSCs) triggers cell activation and trans-differentiation into myofibroblasts.…”

A brain-enriched Drp1 isoform associates with lysosomes, late endosomes, and the plasma membrane

“…Mitochondrial oxygen consumption rates were measured in an XF96 Extracellular Flux Analyzer (Seahorse Bioscience) as described previously described (10,34). Briefly, cells were plated at a density of 5,000 cells/well in an XF 96-well culture microplate and incubated for 24 h. To record oxygen consumption rates, the culture medium was replaced with Seahorse XF base medium supplemented with 25 mM glucose, 1 mM sodium pyruvate, and 2 mM GlutaMAX-I, and then the cells were incubated at 37°C in a CO 2 -free incubator for 1 h. Oxygen consumption rate analysis was initiated with a 13.5-min equilibration step, followed by three cycles of 2 min of mixing and 3 min of measurement.…”

Simultaneous Induction of Glycolysis and Oxidative Phosphorylation during Activation of Hepatic Stellate Cells Reveals Novel Mitochondrial Targets to Treat Liver Fibrosis

“…However, actual glycolytic rat and/or mitochondrial respiration were not quantified. Interestingly, others have shown that plastic-cultured r-aHSCs and LX-2 cells have higher mitochondrial and glycolytic metabolism compared to matrigel-cultured r-aHSCs and LX-2 cells [ 9 ]. Here, we show that the glycolytic rate is increased approximately 3-fold in culture-activated rHSCs versus freshly isolated r-qHSCs.…”

“…Furthermore, inhibiting these metabolic pathways has been shown to prevent the undergoing activation in vitro [ 7 , 8 ]. It has been recently demonstrated that plastic-cultured aHSCs have enhanced oxidative phosphorylation and glycolysis compared to less activated matrigel-cultured aHSCs [ 9 ]. However, functional analyses to quantify metabolic processes that differentiate freshly isolated qHSCs versus culture-activated HSCs have not been reported yet.…”