In vitro interaction of L-Dopa with bacterial adhesins of Helicobacter pylori: An explanation for clinicial differences in bioavailability?

Recent investigations on the pharmacokinetics of levodopa (L-Dopa) indicated that the presence of Helicobacter pylori (HP) in Parkinson disease patients, orally treated with L-Dopa, influences the absorption of this compound, which consequently leads to decreased plasma levels [1,2]. Therefore this work aims to study a potential in vitro interaction of L-Dopa with HP and its surface adhesins. Free L-Dopa was quantified from the incubation supernatants with HP by HPLC. A flow cytometric assay with fluorescence labelled HP was used to investigate the influence of L-Dopa on the bacterial adhesion of HP. FITC-labelled bacteria were preincubated with L-Dopa, followed by incubation with gastric epithelial cells (AGS) and flow cytometric analysis. Quantitative evaluation of time and concentration dependent incubation experiments indicated a significant decrease of L-Dopa concentrations when getting in contact with HP. The reduction of L-Dopa concentrations was determined with 47 to 12% referred to the initial starting concentration, with time-dependency and dependency of the HP density. FITC-labelled HP, preincubated with differing L-Dopa concentrations, was shown to have a significant (p<0.05) reduced bacterial adhesion to AGS cells with maximum reduction of 22±9%. These results demonstrate a direct interaction of L-Dopa with outer membrane proteins of HP, responsible for the adhesion to gastric epithelial cells. By this interaction the unbound L-Dopa concentration in bacterial suspension was strongly reduced. This study suggests a potential in vitro interaction of L-Dopa with HP adhesins, confirming the clinical changes found in pharmacokinetics of L-Dopa therapy by HP-positive Parkinson patients.

References: [1] Pierantozzi, M. et al. (2001) Ann. Neurol. 50:686–687.

[2] Pierantozzi, M. et al. (2001) Neurol. Sci. 22:89–91.