Upregulation of the GABA-transporter GAT-1 in the spinal cord contributes to pain behaviour in experimental neuropathy.

Sciatic nerve ligation in rats (chronic constriction injury (CCI)) induces signs and symptoms that mimic human conditions of neuropathy. The central mechanisms that have been implicated in the pathogenesis of neuropathic pain include increased neuronal excitability, possibly a consequence of decreased availability of spinal GABA. GABA availability is regulated by the presence of the GABA-transporters (GATs). This study investigates the dorsal horn expression of the transporter GAT-1 and its functional involvement towards pain behaviour in the CCI model. Male Lewis rats (total n=37) were subjected to CCI or to a sham procedure. A sub-group of animals was treated with the GAT-1 antagonist NO-711. Behavioural testing was performed pre-surgery and at 7 days post-surgery. Testing included evaluation of mechanical allodynia using Von Frey filaments, thermal allodynia with a hot-plate test and observational testing of spontaneous pain behaviour. Subsequently, spinal protein expression of GAT-1 was assessed by Western blotting. Animals were sacrificed 7 days following surgery. CCI markedly increased mechanical and thermal allodynia and spontaneous pain behaviour after 7 days, while the sham procedure did not. GAT-1 was increased in spinal cord homogenates compared contralateral to the ligation side after 7 days. NO-711 treatment significantly reduced all tested pain behaviour. These data provide evidence for possible functional involvement of GAT-1 in the development of experimental neuropathic pain. The latter can be derived from observed analgesic effects of early treatment with NO-711, a selective GAT-1 inhibitor. The obtained insights support the clinical employment of GAT-1 inhibitors to treat neuropathic pain.

Protection of nigral cell death by bilateral subthalamic nucleus stimulation.

In Parkinson disease (PD), the subthalamic nucleus (STN) becomes hyperactive (disinhibited), which is reported to cause excitotoxic damage to midbrain dopaminergic neurons. Here, we examined whether silencing of the hyperactive STN by chronic bilateral deep brain stimulation (DBS) increased the survival of midbrain dopaminergic neurons in a rat model of PD. High-precision design-based stereologic examination of the total number of neurons and tyrosine tydroxylase (TH) immunoreactive neurons in the substantia nigra pars compacta revealed that STN DBS resulted in a significant survival of these neurons. These data provide the first evidence in vivo that bilateral STN DBS is useful for protecting midbrain dopaminergic neurons from cell death in PD.

Apoptosis and inflammation in renal reperfusion injury.

Ischemia followed by reperfusion (I/R) has cardinal implications in the pathogenesis of organ transplantation and rejection. Apoptosis and inflammation are central mechanisms leading to organ damage in the course of renal I/R. General aspects of apoptosis, morphology, induction, and biochemistry are discussed. Activated caspases, the classical effector enzymes of apoptosis, are able to induce not only apoptosis but also inflammation after I/R in experimental models. This redefines the involvement of apoptosis in I/R injury toward a central and functional role in the development of organ damage. Our purpose is to assess aspects of apoptosis and inflammation in terms of involvement in the pathogenesis of I/R-induced organ damage. Moreover, the implications of recent experimental advances for diagnosis and treatment of renal I/R injury in clinical practice will be discussed.

In vivo expression of Toll-like receptor 2 and 4 by renal epithelial cells: IFN-gamma and TNF-alpha mediated up-regulation during inflammation.

The reported requirement of functional Toll-like receptor (TLR)4 for resistance to Gram-negative pyelonephritis prompted us to localize the expression of TLR2 and TLR4 mRNA in the kidney at the cellular level by in situ hybridization. The majority of the constitutive TLR2 and TLR4 mRNA expression was found to be strategically located in the renal epithelial cells. Assuming that the TLR mRNA expression is representative of apical protein expression, this suggests that these cells are able to detect and react with bacteria present in the lumen of the tubules. To gain insight in the regulation of TLR expression during inflammation, we used a model for renal inflammation. Renal inflammation evoked by ischemia markedly enhanced synthesis of TLR2 and TLR4 mRNA in the distal tubular epithelium, the thin limb of Henle's loop, and collecting ducts. The increased renal TLR4 mRNA expression was associated with significant elevation of renal TLR4 protein expression as evaluated by Western blotting. Using RT-PCR, the enhanced TLR2 and TLR4 mRNA expression was shown to be completely dependent on the action of IFN-gamma and TNF-alpha. These results indicate a potential mechanism of increased immunosurveillance during inflammation at the site in which ascending bacteria enter the kidney tissue, i.e., the collecting ducts and the distal part of the nephron.