Objective: To further characterize mitochondrial dysfunction in LRRK2 G2019S mutant Parkinson disease (PD) patient tissue (M-LRRK2 G2019S), determine whether ursodeoxycholic acid (UDCA) also exerts a beneficial effect on mitochondrial dysfunction in nonmanifesting LRRK2 G2019S mutation carriers (NM-LRRK2 G2019S), and assess UDCA for its beneficial effect on neuronal dysfunction in vivo.Methods: Intracellular adenosine 59-triphosphate (ATP) levels, oxygen consumption, and activity of the individual complexes of the mitochondrial respiratory chain as well as mitochondrial morphology were measured in M-LRRK2G2019S , NM-LRRK2 G2019S , and controls. UDCA was assessed for its rescue effect on intracellular ATP levels in NM-LRRK2G2019S and in a LRRK2 transgenic fly model with dopaminergic expression of LRRK2 G2019S .Results: Crucial parameters of mitochondrial function were similarly reduced in both M- LRRK2G2019S and NM-LRRK2 G2019S with a specific decrease in respiratory chain complex IV activity. Mitochondrial dysfunction precedes changes in mitochondrial morphology but is normalized after siRNA-mediated knockdown of LRRK2. UDCA improved mitochondrial function in NM-LRRK2 G2019 and rescued the loss of visual function in LRRK2 G2019S flies. Conclusion: There is clear preclinical impairment of mitochondrial function in NM-LRRK2 G2019Sthat is distinct from the mitochondrial impairment observed in parkin-related PD. The beneficial effect of UDCA on mitochondrial function in both NM-LRRK2 G2019S and M-LRRK2 G2019S as well as on the function of dopaminergic neurons expressing LRRK2 G2019S suggests that UDCA is a promising drug for future neuroprotective trials. G2019S 5 manifesting LRRK2 G2019S carriers; NM-LRRK2 G2019S 5 nonmanifesting LRRK2 G2019S carriers; PD 5 Parkinson disease; SSVEP 5 steady-state visual evoked potentials; TUDCA 5 taurine conjugate; UDCA 5 ursodeoxycholic acid.
Mutations in the leucine-rich repeat kinase 2 gene are the most common cause of autosomal dominant Parkinson’s disease (PD). To assess the cerebrospinal fluid (CSF) levels of α-synuclein oligomers in symptomatic and asymptomatic leucine-rich repeat kinase 2 mutation carriers, we used enzyme-linked immunosorbent assays (ELISA) to investigate total and oligomeric forms of α-synuclein in CSF samples. The CSF samples were collected from 33 Norwegian individuals with leucine-rich repeat kinase 2 mutations: 13 patients were clinically diagnosed with PD and 20 patients were healthy, asymptomatic leucine-rich repeat kinase 2 mutation carriers. We also included 35 patients with sporadic PD (sPD) and 42 age-matched healthy controls. Levels of CSF α-synuclein oligomers were significantly elevated in healthy asymptomatic individuals carrying leucine-rich repeat kinase 2 mutations (n = 20; P < 0.0079) and in sPD group (n = 35; P < 0.003) relative to healthy controls. Increased α-synuclein oligomers in asymptomatic leucine-rich repeat kinase 2 mutation carriers showed a sensitivity of 63.0% and a specificity of 74.0%, with an area under the curve of 0.66, and a sensitivity of 65.0% and a specificity of 83.0%, with an area under the curve of 0.74 for sPD cases. An inverse correlation between CSF levels of α- synuclein oligomers and disease severity and duration was observed. Our study suggests that quantification of α-synuclein oligomers in CSF has potential value as a tool for PD diagnosis and presymptomatic screening of high-risk individuals.
Primary monolayer cultures of rat hepatocytes were used for studies of long-term and acute effects of hormones on the cyclic AMP system. When hepatocyte lysates were assayed at various times after plating of the cells three major changes in the metabolism of cyclic AMP and its regulation were observed : Glucagon-sensitive adenylate cyclase activity gradually declined in culture. In contrast, catecholamine-sensitive activity, being very low in normal adult male rat liver and freshly isolated hepatocytes, showed a strong and rapid increase after seeding of the cells. Concomitantly, there was an early elevation (peak z 6 h) and a subsequent decrease in activity of both high-& and low-K, cyclic AMP phosphodiesterase. These enzymic changes probably explained the finding that in intact cultured cells the cyclic AMP response to glucagon was diminished for 2-24 h after seeding, followed by an increase in the responsiveness to glucagon as well as to adrenergic agents up to 48 h of culture. Supplementation of the culture media with dexamethasone and/or insulin influenced the formation and breakdown of cyclic AMP in the hepatocytes. Insulin added at the time of plating moderately increased the adenylate cyclase activity assayed at 48 h, while dexamethasone had no significant effect. In the presence of dexamethasone, insulin exerted a stronger, and dosedependent (1 pM-1 pM), elevation of the adenylate cyclase activity in the lysates, particularly of the glucagon responsiveness. Thus, insulin plus dexamethasone counteracted the loss of glucagon-sensitive adenylate cyclase activity occurring in vitro. Kinetic plots of the cyclic AMP phosphodiesterase activity showed three affinity regions for the substrate. Of these, the two with high and intermediate substrate affinity (K, x 1 and x 10 pM) were decreased in the dexamethasone-treated cells. Insulin partly prevented this effect of dexamethasone. Accumulation of cyclic AMP in intact cells in response to glucagon or P-adrenergic agents was strongly increased in cultures pretreated with dexamethasone. The results suggest that insulin and glucocorticoids modulate the effects of glucagon and epinephrine on hepatocytes by exerting long-term influences on the cyclic AMP system. Hepatocytes maintained in vitro as primary cultures [I -101 offer an attractive experimental tool, not only due to the potential usefulness of these cells in investigations of the biology and pharmacology of liver [ll-131, but also because relatively few other model systems exist for long term studies of differentiated epithelial cells in vitro under controlled conditions.We have investigated the cyclic AMP system and its regulation in primary monolayer cultures of adult rat hepatocytes. The studies first intended to explore if the hepatocytes in culture maintain normal formation and degradation of cyclic AMP. Hepatocytes in monolayer possess the enzymes involved in cyclic AMP metabolism [5,, but relatively few details are known. Our results indicate that the cells in culture retain hormone sensitivity, but al...
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