Lindane (gamma-hexachlorocyclohexane) induces internal Ca2+ release and capacitative Ca2+ entry in Madin-Darby canine kidney cells

Biochemical effects induced by the hexachlorocyclohexanes

The hexachlorocyclohexanes (HCHs) are synthetic compounds that have been widely used for the control of pests. The most common HCH isomers are the α-, β-, δ-, and γ-HCH. Although the have the same chlorine substitution pattern, the spatial orientation of chlorine atoms is different on each one of them, resulting in unique structures that have distinct molecular properties. Humans are exposed to individual HCH isomers through various routes, including ingestion of contaminated water or food, absorbed through the skin or by inhalation, and because of their liposolubility, these chemicals are mostly stored in fat-containing tissues. The isomer-specific spectrum of biochemical actions for these compounds has been wee characterized for different endpoints such as enzyme activation, calcium homeostasis, gap junctional intercellular communication, endocrine disruption, and cancer, among others. The interaction with the GABA reception has been one of the most extensively studied properties of the HCHs. For instance, γ-HCH acts as a GABAA channel blocker, whereas α- and δ-HCH potentiate currents , all working as allosteric modulators of the receptor. The changes in calcium homeostasis elicited by HCHs are both isomer and cell type specific. For example, in neurons, both the δ- and γ-isomers of HCH stimulate Ca²+ influx through different voltage-gated Ca²+ channels. In human neutrophils, α-,δ-, and γ-HCH, but not β-HCH, increase intracellular Ca²+ concentrations. This isomer-dependent behavior is also similar to that observed for phospholipase A2 activation and also correlates with oxidative stress generation. On the other hand, there are several lines of evidence suggesting that HCHs alter genomic integrity, and, therefore, these compounds have been classified as possibly carcinogenic to humans . Finally, HCHs have been reported to be endocrine disrupters. In fact, γ- and β-HCH have been shown to have weak estrogenic activity, and together with the α- and the δ-isomer, also interfere with steroidogenesis. In short, the HCH isomers are good examples of structurally related chemicals, for which the geometrical patterns present in each one of the different conformers create structures that possess specific mechanisms of action and toxicological properties.

Lindane-induced generation of reactive oxygen species and depletion of glutathione do not result in necrosis in renal distal tubule cells

Lindane is a chlorinated hydrocarbon pesticide, currently used in prescription shampoos and lotions to treat scabies and lice infestations. Lindane is known to be nephrotoxic; however, the mechanism of action is not well understood. In other organ systems, lindane produces cellular damage by generation of free radicals and oxidative stress. Morphological changes were observed in lindane-treated Madin-Darby canine kidney (MDCK) cells indicative of apoptosis. Lindane treatment induced time-dependent reactive oxygen species (ROS) generation. Onset of ROS generation correlated with an initial increase in total glutathione (GSH) levels above control values, with a subsequent decline in a time-dependent manner. This decline may be attributed to quenching of free radicals by GSH, thereby decreasing the cellular stores of this antioxidant. Necrotic injury was assessed by measuring lactate dehydrogenase (LDH) leakage from the cell after lindane exposure. No significant LDH leakage was noted for all concentrations tested over time. Generation of ROS and alterations in cellular protective mechanisms did not result in necrotic injury in MDCK cells, which corresponds with our morphological findings of lindane-induced apoptotic changes as opposed to necrosis in MDCK cells. Thus, lindane exposure results in oxidative damage and alterations in antioxidant response in renal distal tubule cells, followed by cell death not attributed to necrotic injury.

Does lindane (gamma-hexachlorocyclohexane) increase the rapid delayed rectifier outward K+ current (IKr) in frog atrial myocytes?

BACKGROUND

The effects of lindane, a gamma-isomer of hexachlorocyclohexane, were studied on transmembrane potentials and currents of frog atrial heart muscle using intracellular microelectrodes and the whole cell voltage-clamp technique.

RESULTS

Lindane (0.34 microM to 6.8 microM) dose-dependently shortened the action potential duration (APD). Under voltage-clamp conditions, lindane (1.7 microM) increased the amplitude of the outward current (Iout) which developed in Ringer solution containing TTX (0.6 microM), Cd2+ (1 mM) and TEA (10 mM). The lindane-increased Iout was not sensitive to Sr2+ (5 mM). It was blocked by subsequent addition of quinidine (0.5 mM) or E-4031 (1 microM). E-4031 lengthened the APD; it prevented or blocked the lindane-induced APD shortening.

CONCLUSIONS

In conclusion, our data revealed that lindane increased the quinidine and E-4031-sensitive rapid delayed outward K+ current which contributed to the AP repolarization in frog atrial muscle.