Δ9-tetrahydrocannabinol (Δ9-THC) exerts a direct neuroprotective effect in a human cell culture model of Parkinson's disease.

AIMS: Δ9-tetrahydrocannabinol (Δ9-THC) is neuroprotective in models of Parkinson's disease (PD). Although CB1 receptors are increased within the basal ganglia of PD patients and animal models, current evidence suggests a role for CB1 receptor-independent mechanisms. Here, we utilized a human neuronal cell culture PD model to further investigate the protective properties of Δ9-THC. METHODS: Differentiated SH-SY5Y neuroblastoma cells were exposed to PD-relevant toxins: 1-methyl-4-phenylpyridinium (MPP+), lactacystin and paraquat. Changes in CB1 receptor level were determined by quantitative polymerase chain reaction and Western blotting. Cannabinoids and modulatory compounds were co-administered with toxins for 48 h and the effects on cell death, viability, apoptosis and oxidative stress assessed. RESULTS: We found CB1 receptor up-regulation in response to MPP+, lactacystin and paraquat and a protective effect of Δ9-THC against all three toxins. This neuroprotective effect was not reproduced by the CB1 receptor agonist WIN55,212-2 or blocked by the CB1 antagonist AM251. Furthermore, the antioxidants α-tocopherol and butylhydroxytoluene as well as the antioxidant cannabinoids, nabilone and cannabidiol were unable to elicit the same neuroprotection as Δ9-THC. However, the peroxisome proliferator-activated receptor-gamma (PPARγ) antagonist T0070907 dose-dependently blocked the neuroprotective, antioxidant and anti-apoptotic effects of Δ9-THC, while the PPARγ agonist pioglitazone resulted in protection from MPP+-induced neurotoxicity. Furthermore, Δ9-THC increased PPARγ expression in MPP+-treated SH-SY5Y cells, another indicator of PPARγ activation. CONCLUSIONS: We have demonstrated up-regulation of the CB1 receptor in direct response to neuronal injury in a human PD cell culture model, and a direct neuronal protective effect of Δ9-THC that may be mediated through PPARγ activation.

Changes in iron-regulatory gene expression occur in human cell culture models of Parkinson's disease.

BACKGROUND: Neuronal iron accumulation is thought to be relevant to the pathogenesis of Parkinson's disease (PD), although the mechanism remains elusive. We hypothesized that neuronal iron uptake may be stimulated by functional mitochondrial iron deficiency. OBJECTIVE: To determine firstly whether the mitochondrial toxin, 1-methyl-4-phenylpyridinium iodide (MPP(+)), results in upregulation of iron-import proteins and transporters of iron into the mitochondria, and secondly whether similar changes in expression are induced by toxins with different mechanisms of action. METHODS: We used quantitative PCR and Western blotting to investigate expression of the iron importers, divalent metal transporter, transferrin receptor 1 and 2 (TfR1 and TfR2) and mitoferrin-2 and the iron exporter ferroportin in differentiated SH-SY5Y cells exposed to three different toxins relevant to PD, MPP(+), paraquat (a free radical generator) and lactacystin (an inhibitor of the ubiquitin-proteasome system (UPS)). RESULTS: MPP(+) resulted in increased mRNA and protein levels of genes involved in cellular iron import and transport into the mitochondria. Similar changes occurred following exposure to paraquat, another inducer of oxidative stress. Lactacystin also resulted in increased TfR1 mRNA levels, although the other changes were not found. CONCLUSION: Our results support the hypothesis of a functional mitochondrial iron deficit driving neuronal iron uptake but also suggest that differences exist in neuronal iron handling induced by different toxins.

Cartilage thickness and split-line pattern at the canine humeral trochlea.

OBJECTIVE: To characterise the humeral trochlea in middle to large breed dogs in respect to split-line pattern and cartilage thickness. METHODS: In 15 paired cadaveric elbow joints of mature dogs (>20 kg body weight) collagen network orientation of the hyaline cartilage of the humeral trochlea was visualised using a traditional split-line technique in which a dissecting needle dipped in India ink was inserted into the cartilage (n = 10). Cartilage thickness was measured radiographically on osteochondral plugs harvested at four representative locations within the joint surface of the humeral trochlea (n = 15). RESULTS: The joint surface of the humeral trochlea showed a distinct pattern of centripetally oriented split-lines with less pronounced or even absent split-lines caudo- proximally towards the olecranon fossa. Median cartilage thickness at the canine humeral trochlea was 0.51 mm (interquartile range: 0.42 - 0.61 mm). Centrally, at the region where osteochondrosis lesions commonly occur in middle to large breed dogs, the median cartilage thickness was 0.55 mm (interquartile range: 0.48 - 0.62 mm). CLINICAL SIGNIFICANCE: When focusing on anatomical joint resurfacing while performing osteochondral transplantation at the canine humeral trochlea, transplants should be implanted such that their split-lines are oriented centripetally. Hyaline cartilage thickness of transferred grafts should be in the range of half a millimetre to optimally match the situation at the canine humeral trochlea.