Protective effects of interferon-gamma against methamphetamine-induced neurotoxicity.

Repeated injections of methamphetamine (METH) cause degeneration of striatal dopaminergic nerve terminals. In the present study, we examined the effects of interferon-gamma (IFN-gamma) on METH-induced striatal neurotoxicity in mice. Intraperitoneal injection of IFN-gamma before METH injection significantly prevented METH-induced reduction of striatal dopamine transporter (DAT)-positive signals and hyperthermia. Furthermore, intracerebroventricular injection of IFN-gamma before METH treatment markedly prevented METH-induced reduction of DAT. Interestingly, central IFN-gamma injection had no effect on METH-induced hyperthermia. In addition, IFN-gamma injected centrally after METH treatment, but not systemically, 1h after the final METH injection significantly protected against METH-induced neurotoxicity. Our results suggest that IFN-gamma injected systemically or its related molecule protects against METH-induced neurotoxicity through intracerebral molecular pathways, while it can prevent METH-induced hyperthermia through different molecular events.

[New perspectives on the mechanism of methamphetamine-induced neurotoxicity].

Various hypotheses have been proposed concerning the mechanisms responsible for methamphetamine (METH)-induced neurotoxicity including reactive oxygen species (ROS), dopamine quinones, glutamatergic activity, apoptosis, etc. Recently, new factors regarding glial cell line-derived neurotorophic factor, tumor necrosis factor-alpha, and alpha-synuclein contained in striatal interneural inclusions have also been associated with METH-induced neurotoxicity. In addition, METH-induced self-injurious behavior (SIB) has been proposed to be an acute or immediate behavioral marker predicting the long-lasting neurotoxicity induced by METH. Specifically, it has been proposed that the SIB response may accurately reflect the underlying mechanistic changes occurring in the neuron that eventually result in the long-lasting damage. Several studies have demonstrated that endogenous dopamine (DA) plays an important role in mediating METH-induced neuronal damage. DA release and redistribution from synaptic vesicles to cytoplasmic compartments is thought to involve METH-induced changes in both the vesicular monoamine transporter-2 and DA transporter function. In turn, the consequent elevation of cytosolic auto-oxidizable DA concentrations is thought generate ROS such as superoxide and hydroxyl radicals and cause the DA terminal injury. Finally, the inflammatory response of microglia and glutamatergic toxicity in astrocytes have been related to the METH-induced neurotoxicity. The objective of the present review will be to consolidate the new perspectives in an attempt to formulate a more cohesive explanation of the underlying mechanism responsible for METH-induced DA damage and its early biological markers.

Protective effects of metallothionein against dopamine quinone-induced dopaminergic neurotoxicity.

Dopamine (DA) quinone as DA neuron-specific oxidative stress conjugates with cysteine residues in functional proteins to form quinoproteins. Here, we examined the effects of cysteine-rich metal-binding proteins, metallothionein (MT)-1 and -2, on DA quinone-induced neurotoxicity. MT quenched DA semiquinones in vitro. In dopaminergic cells, DA exposure increased quinoproteins and decreased cell viability; these were ameliorated by pretreatment with MT-inducer zinc. Repeated L-DOPA administration markedly elevated striatal quinoprotein levels and reduced the DA nerve terminals specifically on the lesioned side in MT-knockout parkinsonian mice, but not in wild-type mice. Our results suggested that intrinsic MT protects against L-DOPA-induced DA quinone neurotoxicity in parkinsonian mice by its quinone-quenching property.