Aminochrome as a preclinical experimental model to study degeneration of dopaminergic neurons in Parkinson’s disease

Four decades after L-dopa introduction to PD therapy, the cause of Parkinson's disease (PD) remains unknown despite the intensive research and the discovery of a number of gene mutations and deletions in the pathogenesis of familial PD. Different model neurotoxins have been used as preclinical experimental models to study the neurodegenerative process in PD, such as 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and rotenone. The lack of success in identifying the molecular mechanism for the degenerative process in PD opens the question whether the current preclinical experimental models are suitable to understand the degeneration of neuromelanin-containing dopaminergic neurons in PD. We propose aminochrome as a model neurotoxin to study the neurodegenerative processes occurring in neuromelanin-containing dopaminergic neurons in PD. Aminochrome is an endogenous compound formed during dopamine oxidation and it is the precursor of neuromelanin, a substance whose formation is a normal process in mesencephalic dopaminergic neurons. However, aminochrome itself can induce neurotoxicity under certain aberrant conditions such as (i) one-electron reduction of aminochrome catalyzed by flavoenzymes to leukoaminochrome o-semiquinone radical, which is a highly reactive neurotoxin; or (ii) the formation of aminochrome adducts with alpha-synuclein, enhancing and stabilizing the formation of neurotoxic protofibrils. These two neurotoxic pathways of aminochrome are prevented by DT-diaphorase, an enzyme that effectively reduces aminochrome with two-electrons preventing both aminochrome one-electron reduction or formation alpha synuclein protofibrils. We propose to use aminochrome as a preclinical experimental model to study the neurodegenerative process of neuromelanin containing dopaminergic neurons in PD.     

Early results of bladder-cancer screening in a high-risk population of heavy smokers

OBJECTIVE

To report first results of an early bladder‐cancer detection programme, and to evaluate the detection rate and the diagnostic value of the tests used.

SUBJECTS AND METHODS

Urine samples of 183 screened subjects with a history of smoking of ≥40 pack‐years were collected for analysis with a urinary dipstick test for haematuria, the nuclear matrix protein‐22 test (BladderChek®, Matritech, Inc., Newton, MA, USA), voided urine cytology and a molecular cytology test (UroVysion, Abbott Molecular Inc., Des Plaines, IL, USA). Participants with at least one positive test result had a further evaluation including cystoscopy and radiological imaging. The subjects’ risk factors, test results and histological findings were analysed.

RESULTS

In all, 75 subjects had at least one positive test result and were evaluated further; abnormal histological findings were detected in 18 (24% of those who had cystoscopy, 9.8% of the original 183), 15 of those in the urinary bladder, with pTaG1 (one), carcinoma in situ (two), dysplastic lesions (11) and one an inverted papilloma. In the upper urinary tract, two urothelial tumours (pTaG1 and pTxN2G3) and one renal cell carcinoma (pT1G2) were detected by computed tomography. In summary, six of 183 subjects (3.3%) had a histologically confirmed malignant tumour and another 12 (6.6%) were identified with a possible pre‐cancerous lesion of the urinary tract. The urinary dipstick, BladderChek, cytology and UroVysion detected (i.e. were true‐positive in) nine (50%), one (6%), seven (39%) and 11 (61%) of the 18 tumours found, while they failed to detect nine (50%), 17 (94%), 11 (61%) and seven (39%) of these lesions, respectively. Omitting the urine dipstick test, the BladderChek, cytology or UroVysion from the test setting could have spared 40, five, two or one subjects(s) from unnecessary invasive interventions; however, three, none, two or six lesions, would have been missed. More positive screening tests per subject was associated with a higher probability of a (pre)‐malignant lesion.

CONCLUSION

Screening a high‐risk group with a history of smoking of ≥40 pack‐years showed a significant proportion (3.3%) with malignancy. These first results are encouraging and warrant continuation of the screening programme. In this series the most efficient screening tool was the combination of UroVysion, cytology and urinary dipstick testing. Of special scientific interest will be the follow‐up of those patients with a possible pre‐cancerous lesion.     

Ro5-4864 promotes neonatal motor neuron survival and nerve regeneration in adult rats

The translocator protein (18 kDa; TSPO), formerly known as the peripheral benzodiazepine receptor, is an outer mitochondrial membrane protein that associates with the mitochondrial permeability transition pore to regulate both steroidogenesis and apoptosis. TSPO expression is induced in adult dorsal root ganglion (DRG) sensory neurons after peripheral nerve injury and a TSPO receptor ligand, Ro5-4864, enhances DRG neurite growth in vitro and axonal regeneration in vivo . We have now found that TSPO is induced in neonatal motor neurons after peripheral nerve injury and have evaluated its involvement in neonatal and adult sensory and motor neuron survival, and in adult motor neuron regeneration. The TSPO ligand Ro5-4864 rescued cultured neonatal DRG neurons from nerve growth factor withdrawal-induced apoptosis and protected neonatal spinal cord motor neurons from death due to sciatic nerve axotomy. However, Ro5-4864 had only a small neuroprotective effect on adult facial motor neurons after axotomy, did not delay onset or prolong survival in SOD1 mutant mice, and failed to protect adult DRG neurons from sciatic nerve injury-induced death. In contrast, Ro5-4864 substantially enhanced adult facial motor neuron nerve regeneration and restoration of function after facial nerve axotomy. These data indicate a selective sensitivity of neonatal sensory and motor neurons to survival in response to Ro5-4864, which highlights that survival in injured immature neurons cannot necessarily predict success in adults. Furthermore, although Ro5-4864 is only a very weak promoter of survival in adult neurons, it significantly enhances regeneration and functional recovery in adults.     

Genetic deletion of synapsin II reduces neuropathic pain due to reduced glutamate but increased GABA in the spinal cord dorsal horn

The synaptic vesicle protein synapsin II is specifically expressed in synaptic terminals of primary afferent nociceptive neurons and regulates transmitter release in the spinal cord dorsal horn. Here, we assessed its role in nerve injury-evoked molecular and behavioral adaptations in models of peripheral neuropathic pain using mice genetically lacking synapsin II. Deficiency of synapsin II resulted in reduced mechanical and cold allodynia in two models of peripheral neuropathic pain. This was associated with decreased glutamate release in the dorsal horn of the spinal cord upon sciatic nerve injury or capsaicin application onto the sciatic nerve and reduced calcium signals in spinal cord slices upon persistent activation of primary afferents. In addition, the expression of the vesicular glutamate transporters, VGLUT1 and VGLUT2, was strongly reduced in synapsin II knockout mice in the spinal cord. Conversely, synapsin II knockout mice showed a stronger and longer-lasting increase of GABA in lamina II of the dorsal horn after nerve injury than wild type mice. These results suggest that synapsin II is involved in the regulation of glutamate and GABA release in the spinal cord after nerve injury, and that a imbalance between glutamatergic and GABAergic synaptic transmission contributes to the manifestation of neuropathic pain.     

High ligation combined with stripping and endovenous laser ablation of the great saphenous vein: early results of a randomized controlled study

OBJECTIVE: This study compared postoperative patient comfort and the surgical outcome of endovenous laser ablation (EVLA) or stripping of the great saphenous vein, both performed in conjunction with high ligation. METHODS: The study randomized 100 patients with primary trunk varicosities of the great saphenous vein (CEAP clinical class II to IV) to EVLA or stripping. The success of surgery was followed-up by duplex ultrasound imaging at 1, 4, and 16 weeks. Primary end points were the size of the hematoma 1 week after the operation and the preoperative disease-specific Chronic Venous Insufficiency Questionnaire (CIVIQ) quality of life score compared with 4 weeks postoperatively. Secondary end points were postoperative symptoms (pain, use of analgesics, paresthesia at the ankle, residual hematoma), complications, time taken to resume work, the patient's satisfaction with the cosmetic outcome, and the CIVIQ quality of life score at 16 weeks. RESULTS: The groups were well matched at baseline. In all, 95 patients could be followed up in accordance with the protocol. The treatment was successful in all patients. Endovenous laser ablation was associated with an occlusion rate of 100%. Hematomas were significantly smaller after EVLA (median [quartiles]) at 125 (55-180) cm(2) vs stripping 200 (123-269) cm(2) (P = .001). No difference was registered between groups for the CIVIQ quality of life score, with EVLA at -1.25 (-7.5-11.25) vs stripping at 4.38 (-5.94-14.38; P = .34). Several postoperative symptoms favored EVLA, but the only significant differences were seen in the minor side effects of surgery at 1 and 4 weeks and discomfort due to paresthesia at the ankle in the first postoperative week. EVLA was associated with a longer period of time until return to work (median [quartiles]) of 20 (14-25.5) days vs 14 (12.8-25) days (P = .054). CONCLUSION: Endovenous laser ablation combined with high ligation is safe and effective. Postoperative hematomas are significantly smaller than those after stripping. Short-term quality of life is at least as good as that after stripping. The long-term results warrant further investigation.     

Recombinant human growth hormone treatment of children with chronic renal failure: long-term (1- to 3-year) outcome

Treatment of nine boys, aged 2.8–16.3 years, with growth retardation consequent to chronic renal failure (CRF), with recombinant human growth hormone (rhGH) for 12–36 months demonstrated a significant improvement in growth velocity at each 12-month interval compared with that achieved the year prior to treatment. Despite the acceleration in growth velocity the bone age did not increase more than the increase in chronological age during the period of treatment. The mean calculated creatinine clearance did not decrease significantly during the 36 months of treatment; however, two patients required institution of dialysis at 18 and 30 months following the initiation of rhGH treatment. There was no exacerbation of the glucose intolerance of uremia following rhGH treatment. Currently, six of seven patients who have been treated for more than 24 months have achieved sufficient acceleration of growth velocity to attain a standard deviation score that was more positive than –2.00, and are above the 5th per centile for chronological age on the growth curve. These data indicate that rhGH treatment of growthretarded children with CRF results in accelerated growth velocity during the 2nd and 3rd years of treatment, and demonstrate the potential for such children to achieve normal stature for chronological age despite the continued presence of renal failure.     

Capsaicin-sensitive extrinsic afferents are involved in acid-induced activation of distinct myenteric neurons in the rat stomach

Challenge of the rat gastric mucosa with 0.5 mol L(-1) HCl activates nitrergic neurons in the myenteric plexus as visualized by c-Fos immunohistochemistry. In the present study, we characterized the activated neurons more extensively by their chemical coding and investigated whether a neural pathway that involves capsaicin-sensitive extrinsic afferents and/or cholinergic neurons transmitting via nicotinic receptors contributes to the activation of myenteric neurons. In multiple labelling experiments, c-Fos was examined for co-localization with nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), enkephalin (ENK), gastrin-releasing peptide (GRP), substance P (SP), calbindin D-28k (CALB) and neurofilament 145 (NF 145). All c-Fos-positive neurons were immunoreactive for NOS, VIP, NPY and NF 145, but not for SP, ENK, GRP and CALB. Nerve fibres co-expressing NOS, VIP and NPY were predominantly found in the external muscle layer and in the muscularis mucosae but rarely in the mucosa. Pre-treatment with capsaicin or hexamethonium or a combination of both pre-treatments reduced HCl-induced c-Fos expression by 54, 66 and 63%, respectively. Acid challenge of the stomach, therefore, leads to activation of presumably inhibitory motor neurons responsible for muscle relaxation. Activation of these neurons is partly mediated by capsaicin-sensitive afferents and involves ganglionic transmission via nicotinic receptors.     

Reduction and recovery of neuronal size in the cochlear nucleus of the chicken following aminoglycoside intoxication

The effect of aminoglycoside intoxication on the cross-sectional area of neurons in nucleus magnocellularis (NM) was studied in neonatal chickens. Birds received daily injections of 100 mg/kg body weight of gentamicin for 10 consecutive days. Cell area was measured at five different tonotopic regions along the posterior-to-anterior dimension of NM (low-to-high frequency) after post-treatment survival times of 8, 23 and 40 days. Gentamicin caused a reversible reduction of cell area that varied as a function of location and survival time. Significant decreases of cell area occurred only in the rostral half of the nucleus. Cell area was reduced at 8 and 23 days survival and recovered to near control values by 40 days post-treatment. Body weight, brain weight and the cross-sectional area of cerebellar Purkinje neurons were also reduced but did not recover. The present results show that aminoglycoside toxicity can affect auditory neurons in the brain. It is suggested that two factors contributed to the changes in NM neuron size: (1) Processes specifically related to the loss and regeneration of cochlear hair cells, most likely changes in afferent activity. (2) A general retardation in growth.