Cell Volume Regulation and Apoptotic Volume Decrease in Rat Distal Colon Superficial Enterocytes

Abstract

Background: The colon epithelium is physiologically exposed to osmotic stress, and the activation of cell volume regulation mechanisms is essential in colonocyte physiology. Moreover, colon is characterized by a high apoptotic rate of mature cells balancing the high division rate of stem cells. Aim: The aim of the present work was to investigate the main cell volume regulation mechanisms in rat colon surface colonocytes and their role in apoptosis. Methods: Cell volume changes were measured by light microscopy and video imaging on colon explants; apoptosis sign appearance was monitored by confocal microscopy on annexin V/propidium iodide labeled explants. Results: Superficial colonocytes showed a dynamic regulation of their cell volume during anisosmotic conditions with a Regulatory Volume Increase (RVI) response following hypertonic shrinkage and Regulatory Volume Decrease (RVD) response following hypotonic swelling. RVI was completely inhibited by bumetanide, while RVD was completely abolished by high K⁺ or iberiotoxin treatment and by extracellular Ca²⁺ removal. DIDS incubation was also able to affect the RVD response. When colon explants were exposed to H₂O₂ as apoptotic inducer, colonocytes underwent an isotonic volume decrease ascribable to Apoptotic Volume Decrease (AVD) within about four hours of exposure. AVD was shown to precede annexin V positivity. It was also inhibited by high K⁺ or iberiotoxin treatment. Interestingly, treatment with iberiotoxin significantly inhibited apoptosis progression. Conclusions: In rat superficial colonocytes K⁺ efflux through high conductance Ca²⁺-activated K⁺ channels (BK channels) was demonstrated to be the main mechanism of RVD and to plays also a crucial role in the AVD process and in the progression of apoptosis.

Nanomorphological and mechanical reconstruction of mesenchymal stem cells during early apoptosis detected by atomic force microscopy

“…In early apoptosis, the elastic modulus and volume of the BMSCs increasingly decreased while the roughness of the cell surface gradually increased, and numerous filamentous structures crossed the membrane and remained on the surface. These findings are basically consistent with the results of the stiffness, volume and surface roughness during the apoptosis of cancer cells induced by different factors in the literatures [Zhang et al, 2016;Antico et al, 2013].…”

Nanomorphological and mechanical reconstruction of mesenchymal stem cells during early apoptosis detected by atomic force microscopy

“…In early apoptosis, the elastic modulus and volume of the BMSCs significantly decreased while the roughness of the cell surface gradually increased, and numerous filamentous structures crossed the membrane and remained on the surface. These findings are basically consistent with the results of the stiffness, volume and surface roughness during the apoptosis of cancer cells induced by different factors in the literatures [Zhang et al, 2016; Antico et al, 2013]. However, these studies did not delve into why the surface of the cells became rougher.…”

Cadmium affects osmotic phase and regulatory volume decrease in cultured human embryonic kidney cells

“…47 Since in the present investigation an impaired swelling capacity under hyposmotic challenge was seen under both 1 and 10 µM Cd 2+ treatment, an oxidative effect of the metal comparable to what observed by H2O2-treated HEK 293 cells may be even suggested.…”