Apoptogenic effect of the lipophilic o-naphthoquinone CG 10-248 on rat hepatocytes: light and electron microscopy studies

CG 10-248 (3,4-dihydro-2,2-dimethyl-9-chloro-2H-naphtho[1,2b]pyran-5,6-dione; CG-NQ), a beta-lapachone analogue, modified the ultrastructure of rat hepatocytes, as demonstrated by light and electron microscopy. After 4 h incubation with 100 microM CG-NQ, the following effects were observed: (a) nuclear chromatin condensation; (b) chromatin fragmentation; (c) displacement of mitochondria, concentrated around the nucleus; (d) disruption or expansion of mitochondrial outer or inner membranes, respectively; (e) displacement and alteration of endoplasmic reticulum (rough and smooth); (f) decrease of microvilli; (g) blebbing of plasma membrane and production of apoptotic bodies formed by folding of plasma membrane fragments around mitochondria or peroxysomes; and (h) production of hydrogen peroxide. Expression of such effects varied according to hepatocyte samples and taken together strongly support an apoptotic action of CG-NQ dependent on reactive oxygen species. (AU)

Apoptogenic effect of the lipophilic o-naphthoquinone CG 10-248 on rat hepatocytes: light and electron microscopy studies

CG 10-248 (3,4-dihydro-2,2-dimethyl-9-chloro-2H-naphtho[1,2b]pyran-5,6-dione; CG-NQ), a beta-lapachone analogue, modified the ultrastructure of rat hepatocytes, as demonstrated by light and electron microscopy. After 4 h incubation with 100 microM CG-NQ, the following effects were observed: (a) nuclear chromatin condensation; (b) chromatin fragmentation; (c) displacement of mitochondria, concentrated around the nucleus; (d) disruption or expansion of mitochondrial outer or inner membranes, respectively; (e) displacement and alteration of endoplasmic reticulum (rough and smooth); (f) decrease of microvilli; (g) blebbing of plasma membrane and production of apoptotic bodies formed by folding of plasma membrane fragments around mitochondria or peroxysomes; and (h) production of hydrogen peroxide. Expression of such effects varied according to hepatocyte samples and taken together strongly support an apoptotic action of CG-NQ dependent on reactive oxygen species.

[Physiopathologic effects of nitric oxide and their relationship with oxidative stress]. / Efectos fisiopatológicos del óxido nítrico y su relación con el estrés oxidativo.

Nitric oxide (NO.) is produced from L-arginine, as result of a reaction catalyzed by the enzyme nitric oxide synthase (NOS). The reaction is the sole source of NO. in animal tissues. NO. can control physiological processes (or systems) such as (a) blood pressure; (b) relaxation of arterial smooth muscle; (c) platelet aggregation and adhesion; (d) neurotransmission; (e) neuroendocrine secretion. NO. contributes to the killing of pathogenic microorganisms and tumoral cells by phagocytes. NO. reacts with superoxide anion thus producing peroxynitrite, a cytotoxic ion capable of destroying many biological targets. The superoxide/peroxinitrite balance determines the ONOO- production and, accordingly, is essential for the development of hypertension, atherosclerosis, neurodegenerative diseases, viral infections, ischemia-reperfusion injury, and cancer.

Effect of 5-nitroindole on adenylate energy charge, oxidative phosphorylation, and lipid peroxidation in rat hepatocytes.

5-Nitroindole (NI), a mutagenic nitroarene, was assayed for cytotoxic effects on rat hepatocytes. After incubation with 25-100 microM NI, the adenylate energy charge of the hepatocytes decreased significantly as a result of the decrease in ATP and the increase in AMP. ATP depletion correlated well with the effects of NI on mitochondrial electron transfer and energy transduction in hepatocytes. Thus, NI (a) inhibited the antimycin-sensitive hepatocyte respiration; (b) inhibited NADH oxidation by disrupted hepatocyte mitochondria; (c) inhibited L-malate-L-glutamate oxidation by ADP-supplemented mitochondria; (d) in the absence of ADP, stimulated the same substrates and also succinate oxidation by mitochondria; (e) released the latent ATPase activity of mitochondrial F1F0-ATP synthase; (f) shifted the redox level of reduced cytochromes (c + c1) and b towards the oxidized state; (g) inhibited NADH oxidation by disrupted mitochondria in the vicinity of the NADH-dehydrogenase flavoprotein; (h) inhibited Ca2+ uptake by mitochondria using L-malate-L-glutamate as an energy source; (i) inhibited valinomycin-induced, endogenously energized K+ uptake, with little effect on the ATP-induced uptake; and (j) inhibited the MgATP-dependent contraction of Ca(2+)-swollen mitochondria. NI inhibited lipid peroxidation in hepatocytes and also in substrate-supplemented liver microsomes and mitochondria, thus ruling out hydroperoxides as a cause of NI cytotoxicity. Long-term incubation with NI produced loss of hepatocyte viability, as indicated by lactate dehydrogenase leakage.