Uncoupling of oxidative phosphorylation of rat liver mitochondria by chinoform

A cell-based phenotypic assay to identify cardioprotective agents

RATIONALE

Tissue ischemia/reperfusion (IR) injury underlies several leading causes of death such as heart-attack and stroke. The lack of clinical therapies for IR injury may be partly due to the difficulty of adapting IR injury models to high-throughput screening (HTS).

OBJECTIVE

To develop a model of IR injury that is both physiologically relevant and amenable to HTS.

METHODS AND RESULTS

A microplate-based respirometry apparatus was used. Controlling gas flow in the plate head space, coupled with the instrument's mechanical systems, yielded a 24-well model of IR injury in which H9c2 cardiomyocytes were transiently trapped in a small volume, rendering them ischemic. After initial validation with known protective molecules, the model was used to screen a 2000-molecule library, with post-IR cell death as an end point. Po2 and pH monitoring in each well also afforded metabolic data. Ten protective, detrimental, and inert molecules from the screen were subsequently tested in a Langendorff-perfused heart model of IR injury, revealing strong correlations between the screening end point and both recovery of cardiac function (negative, r2=0.66) and infarct size (positive, r2=0.62). Relationships between the effects of added molecules on cellular bioenergetics and protection against IR injury were also studied.

CONCLUSIONS

This novel cell-based assay can predict either protective or detrimental effects on IR injury in the intact heart. Its application may help identify therapeutic or harmful molecules.

Experimental clioquinol intoxication in rats: abnormalities in optic nerves and small nerve cells of dorsal root ganglia

Pathological abnormalities in the central (CNS) and peripheral nervous system (PNS) were produced in rats by daily administration of 300-400 mg/kg clioquinol for 7-40 days. The changes comprised axonal degeneration of optic nerve fibers and mitochondrial swellings in small nerve cells of dorsal root ganglia. There were occasional myelin splittings in the spinal nerve roots. No apparent changes were observed in the spinal cord or peripheral nerves. Similar changes were occasionally encountered to a lesser extent in control rats by restricting the diet and water to maintain the body weight comparable to the ranges of experimental animals. It seemed that not only clioquinol intoxication but nutritional deficiency also contributed, in part, to the production of these CNS and PNS abnormalities. The possibility of the presence of peripheral neuropathy in subacute myelooptic neuropathy is discussed.

Lipid peroxidation caused by chinoform-ferric chelate in cultured neural retinal cells

Incorporation of chinoform-ferric chelate was demonstrable in cultured neural retinal cells of chick embryos after 1 h of incubation, and the lipid peroxide level in the cells was increased strikingly 1 h thereafter. On the other hand, free ferric ions were scarcely incorporated into the cells, and a significant increase in the lipid peroxide level in the cells was not observed. These data indicate that chinoform is carrier of iron for its passage through cell membranes and that the incorporated iron induces lipid peroxidation which in turn leads to neural cell degeneration.

Percutaneous absorption and disposition of iodochlorhydroxyquin in dogs

The percutaneous absorption and disposition of iodochlorhydroxyquin (5-chloro-7-iodo-8-quinolinol; I) from a 3% cream were studied in five dogs over a 28-d topical treatment period. Plasma levels, determined by HPLC, were 0.275-0.525 microgram/mL. The steady-state elimination rate of total I in urine was 2.4-3.0 mg/d. The apparent elimination rate constant and half-life were 0.25 +/- 0.05 d-1 and 3.1 +/- 0.5 d, respectively. Greater than 50% of topically applied I was absorbed over 16 h. Occlusion of the skin without the drug indicated that the skin acted as a reservoir for the drug. Feces analysis for iodochlorhydroxyquin from one dog showed that 27.1 +/- 8.5 mg/d was eliminated via this route. Tissue levels of I 15 d after the 28-d topical treatment were 0.7 microgram/g of liver, 0.2 microgram/g of kidney, and 0.8 microgram/g of mesenteric fat. The apparent rate constants of plasma level decline after a 100-mg iv bolus dose of I were alpha = 3.9 h-1 and beta = 0.6 h-1. The urinary elimination after intravenous administration was biphasic. The rate constant for the slow elimination phase was 0.4 +/- 0.1 d-1, and the half-life was 2.0 +/- 0.5 d. The primary neurological symptoms observed during topical treatment were ataxia and hind limb paralysis. Microscopic examination revealed liver necrosis. A weight loss of 15.3 +/- 2.7% was also observed over the 28-d topical treatment period. The results indicate that significant percutaneous absorption of I occurs, and that chronic high-dose topical treatment may lead to toxicity.

Inhibition of interferon action by chinoform

Chinoform, iodochlorhydrozyquin, was found to suppress the antiviral action of interferon. Chick embryo fibroblast cells treated with the mixture of interferon and chinoform were more sensitive to Sindbis virus infection than cells treated with interferon alone. No evidence for a direct inactivation of interferon molecule by chinoform was obtained. Treatment with chinoform of cells previously exposed to interferon also removed a cellular antiviral state induced by interferon. Chinoform suppressed intracellular ribonucleic acid (RNA) and protein syntheses. It is suggested that the inhibitory effect of chinoform on the action of interferon is due to a suppression of continued production of antiviral proteins.

Effect of albumin on uncoupling of oxidative phosphorylation by chinoform in rat liver mitochondria

Addition of serum albumin diminished the uncoupling effect of chinoform on oxidative phosphorylation in rat liver mitochondria. Upon increasing the concentration of magnesium ions in the medium, the action of serum albumin was diminished. These results indicate that serum albumin combines with chinoform in competition with magnesium ions.