Mitochondrial Membrane Potential (DeltaPsi) and Ca^2+-Induced Differentiation in HaCaT Keratinocytes

Abstract

We have used the human calcium- and temperature-dependent (HaCaT) keratinocyte cell line to elucidate mechanisms of switching from a proliferating to a differentiating state. When grown in low calcium medium (<0.1 mM) HaCaT cells proliferate. However, an increase in the calcium concentration of the culture medium, [Ca²⁺]₀, induces growth arrest and the cells start to differentiate. Numerous studies have already shown that the increase in [Ca²⁺]₀ results in acute and sustained increases in intracellular calcium concentration, [Ca²⁺]_i. We find that the Ca²⁺-induced cell differentiation of HaCaT cells is also accompanied by a significant decrease in mitochondrial membrane potential, DeltaPsi. By combining patch-clamp electrophysiological recordings and microspectrofluorimetric measurements of DeltaPsi on single cells, we show that the increase in [Ca²⁺]_i led to DeltaPsi depolarization. In addition, we report that tetraethylammonium (TEA), a blocker of plasma membrane K⁺ channels, which is known to inhibit cell proliferation, and 4,4’-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), a blocker of plasma membrane Cl^– channels, also affect DeltaPsi. Both these agents stimulate HaCaT cell differentiation. These data therefore strongly suggest a direct causal relationship between depolarization of DeltaPsi and the inhibition of proliferation and induction of differentiation in HaCaT keratinocytes.

Evaluation of the localization and biological effects of PAMAM G3 dendrimer-biotin/pyridoxal conjugate as HaCaT keratinocyte targeted nanocarrier

“…On the other hand, studies by Colombo and others (Colombo et al, 2017) and others (Stein et al, 1997;Magcwebeba et al, 2012) had documented that HaCaT cells can be applied as a reliable model for in vitro inflammation studies and repair processes under optimal, controlled conditions. That includes specificity of the stimulating agent: UV light, allergens or irritants (Kim et al, 2012, Hoffman et al, 2013, carbon nanomaterials (Pelin et al, 2017), palmitic acid (Zhou et al, 2013), as well as cell density confluence/non-confluence (Shabo et al, 2001), and low/high calcium ion concentrations (Savignan et al, 2004;Borowiec et al, 2013).…”