Association of high levels of plasma free dopamine with future coronary events in patients with coronary artery disease

Where Is Dopamine and how do Immune Cells See it?: Dopamine-Mediated Immune Cell Function in Health and Disease

Dopamine is well recognized as a neurotransmitter in the brain, and regulates critical functions in a variety of peripheral systems. Growing research has also shown that dopamine acts as an important regulator of immune function. Many immune cells express dopamine receptors and other dopamine related proteins, enabling them to actively respond to dopamine and suggesting that dopaminergic immunoregulation is an important part of proper immune function. A detailed understanding of the physiological concentrations of dopamine in specific regions of the human body, particularly in peripheral systems, is critical to the development of hypotheses and experiments examining the effects of physiologically relevant dopamine concentrations on immune cells. Unfortunately, the dopamine concentrations to which these immune cells would be exposed in different anatomical regions are not clear. To address this issue, this comprehensive review details the current information regarding concentrations of dopamine found in both the central nervous system and in many regions of the periphery. In addition, we discuss the immune cells present in each region, and how these could interact with dopamine in each compartment described. Finally, the review briefly addresses how changes in these dopamine concentrations could influence immune cell dysfunction in several disease states including Parkinson's disease, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, as well as the collection of pathologies, cognitive and motor symptoms associated with HIV infection in the central nervous system, known as NeuroHIV. These data will improve our understanding of the interactions between the dopaminergic and immune systems during both homeostatic function and in disease, clarify the effects of existing dopaminergic drugs and promote the creation of new therapeutic strategies based on manipulating immune function through dopaminergic signaling. Graphical Abstract.

Efficient biocatalyst of L-DOPA with Escherichia coli expressing a tyrosine phenol-lyase mutant from Kluyvera intermedia

L-DOPA (L-dihydroxyphenylalanine) is a promising drug for Parkinson's disease and thereby has a growing annual demand. Tyrosine phenol-lyase (TPL)-based catalysis is considered to be a low-cost yet efficient route for biosynthesis of L-DOPA. TPL is a tetrameric enzyme that catalyzes the synthesis of L-DOPA from pyrocatechol, sodium pyruvate, and ammonium acetate. The implementation of TPL for L-DOPA production has been hampered and the need for the most efficient TPL source with higher L-DOPA production and substrate conversion rate is prevailing. This study involves identifying a novel TPL from Kluyvera intermedia (Ki-TPL) and displayed a robust expression in Escherichia coli. The recombinant strain YW000 carrying Ki-TPL proved strong catalytic activity with a highest L-DOPA yield compared with 16 other TPLs from different organisms. With a further aim to improve this efficiency, random mutagenesis of Ki-TPL was performed and a mutant namely YW021 was obtained. The whole cells of YW021 as biocatalyst yielded 150.4 g L^-1 of L-DOPA with a 99.99 % of pyrocatechol conversion at the optimum condition of pH 8.0 at 25 °C, which is the highest level reported to date. Further, the homology modeling and structural analysis revealed the mutant residues responsible for the extensive L-DOPA biosynthesis.

Relation of Stress Hormones (Urinary Catecholamines/Cortisol) to Coronary Artery Calcium in Men Versus Women (from the Multi-Ethnic Study of Atherosclerosis [MESA])

The relation between high levels of psychosocial stress and the development of coronary artery disease (CAD) has been increasingly recognized, especially in women. We hypothesized that simple biomarkers of stress, urinary catecholamines/cortisol levels, are associated with more coronary artery calcium (CAC), an indicator of CAD, and that this relation is stronger in women compared with men. Using data from the Multi-Ethnic Study of Atherosclerosis Stress study, we examined the relation between urinary catecholamines/cortisol and CAC. The study cohort (n = 654) was 53% women, and 56.4% of the cohort had detectable CAC. Multivariable regression analyses assessed the relation between urinary catecholamines/cortisol and CAC (odds CAC >0 through logistic and ln CAC through Tobit model). There was an association between increased cortisol and increased CAC and an inverse association between dopamine and CAC. These relations were seen in men and women, with no difference between the genders. In conclusion, higher cortisol and lower dopamine levels are independently associated with higher CAC to a similar degree in men and women. These simple urinary biomarkers contribute to our understanding of the role of stress in the pathogenesis of CAD and may be incorporated into future strategies to prevent and treat CAD.

Ranolazine Therapy Reduces Non-ST-Segment-Elevation Myocardial Infarction and Unstable Angina in Coronary Disease Patients with Angina

High sympathetic tone and cardiac autonomic neuropathy (CAN) are associated with major adverse cardiac events (MACE). We have shown ranolazine (RAN) improves autonomic function. RAN was introduced to 51 successive anginal CD patients (RANCD). A control group of 54 successive nonanginal CD patients (NORANCD) continued baseline therapy. Mean study duration was 6.1 years, which included semi-annual autonomic function measures (ANX 3.0, ANSAR Medical Technologies, Inc., Philadelphia, PA) and yearly myocardial perfusion SPECT studies (MPI). MACE were experienced by 29% RANCD patients versus 46% NORANCD patients (p = 0.0105). The patients from both groups with abnormal parasympathetic and sympathetic (P&S) measures and MACE totaled 52 of those patients with MACE versus 17% of those patients without MACE (p = 0.0274). Abnormal MPI was demonstrated in 35% of those with abnormal (P&S) measures and MACE versus 12% without MACE. Sympathovagal balance (SB) was lower, indicating higher, relative parasympathetic tone (known to be cardioprotective) in the RANCD group. Acute coronary syndromes occurred 4.5 times as often in NORANCD patients. High SB occur more frequently than abnormal MPI in CD patients experiencing MACE. In addition to increased myocardial blood flow as its proposed mechanism of angina relief, RAN improves P&S measures, a potentially new mechanism whereby RAN improves outcomes.

Quantitative determination of free and total dopamine in human plasma by LC–MS/MS: the importance of sample preparation

Background: Two methods have been developed and validated for the determination of free and total dopamine in human plasma. They are based on solid-phase extraction of the analyte from the matrix by covalent complexation with phenylboronic acid, followed by derivatization with ethylchloroformate. The derivative is quantified by reversed-phase liquid chromatography on a C18 column and positive electrospray ionization MS/MS. Results: The high selectivity obtained, in combination with the stable and relatively non-polar nature of the derivatized analyte, enables the reliable quantification of dopamine in the range 0.05 to 20 ng/ml in a 5 min run time, using only 100 µl of sample. Total dopamine concentrations are determined (range 1 to 400 ng/ml) by including an acidic hydrolysis step, which converts the sulphate and glucuronide conjugates to free dopamine prior to extraction. The method was applied to quantify free and total dopamine levels in human plasma after dosing with the anti-Parkinson’s drug combination L-dopa/carbidopa with and without entacapone. Conclusion: A sensitive and selective LC–MS/MS method has been developed and validated for the determination of free and total dopamine in human plasma. This article demonstrates how essential careful optimization of the sample preparation procedures was for developing a successful method.

Improving myocardial perfusion by percutaneous coronary intervention reduces central sympathetic activity in stable angina

BACKGROUND

By stimulating sympathetic afferents, repetitive myocardial ischemia induces a state of increased sympathetic tone.

HYPOTHESIS

Removing the ischemic trigger by revascularization using percutaneous coronary intervention (PCI) might thus reduce central sympathetic activity in symptomatically stable angina patients.

METHODS

A total of 20 patients with stable angina > or = New York Heart Association (NYHA) class II with persistent symptoms despite maximal pharmacological therapy and a clinical indication for PCI, were included in our study. Sympathetic nervous system activity was measured before and 1 month after PCI by a combination of techniques: direct muscle sympathetic nerve activity (MSNA), neurochemical (plasma catecholamine levels), and heart rate variability (HRV).

RESULTS

All patients completed the study. After PCI there was a significant reduction in MSNA (pre-PCI 72 +/- 4 to post-PCI 53 +/- 4 burst/100 beats, P < .05) and low frequency/high frequency (LF/HF) ratio (3.7 +/- 0.6 vs 2.4 +/- 0.4, P < .05) consistent with a decline in sympathetic activity. Plasma norepinephrine levels were reduced after PCI, but this difference did not reach statistical significance (1.84 +/- 0.17 vs 1.73 +/- 0.13 nmol/L, P = not significant).

CONCLUSION

Coronary revascularization by PCI reduces sympathetic activity in patients with established myocardial ischemia.

Optimization of process parameters for the production of tyrosine phenol lyase by Citrobacterfreundii MTCC 2424

The process optimization using technological combinations for the production of tyrosine phenol lyase by Citrobacter freundii MTCC 2424 has been carried out in this study. The maximum production of tyrosine phenol lyase (0.15 U) was obtained by culturing C. freundii MTCC 2424 in a medium containing (g/l) meat extract 5.0, yeast extract 5.0, peptone 2.5, and l-tyrosine 1.0 at 25 degrees C for 16 h in a temperature controlled orbital shaker. A 2.5-fold increase in enzyme activity with 1.3-fold decrease in the cost of enzyme production (in terms of media components) was achieved by using different technological combinations. The process optimization using technological combinations allowed quick optimization of large number of variables, which helps in designing of suitable fermentation conditions for the cost-effective production of tyrosine phenol lyase. Moreover, this also provides information for balancing the nutrient concentration with minimum experimentation.

Altered interaction between plasminogen activator inhibitor type 1 activity and sympathetic nerve activity with aging

BACKGROUND

It has been reported that sympathetic nerve activity (SNA) is associated with fibrinolysis, but the interaction between SNA and the fibrinolytic system with aging has not been elucidated in humans. The purpose of this study was to examine the effect of age-related SNA on the activity of plasminogen activator inhibitor type 1 (PAI-1) and tissue plasminogen activator (tPA) using muscle SNA (MSNA).

METHODS AND RESULTS

This study included 16 young subjects (mean age 26.1 years) and 10 aged subjects (mean age 56.9 years). Lower body negative pressure (LBNP) was performed at -40 mmHg for 30 min. LBNP significantly increased both tPA and PAI-1 activity (from 5.2+/-0.5 to 7.3+/-1.2 IU/ml and from 2.85+/-0.68 to 4.06+/-0.73 U/ml, p<0.01, respectively) in the aged group. In the young group, tPA activity tended to increase, whereas PAI-1 activity was unchanged. There was a correlation between MSNA and PAI-1 activity in the aged group (r=0.47, p<0.01).

CONCLUSIONS

SNA in an aging subject leads to an increase in the activity of PAI-1, which indicates that an altered interaction between SNA and PAI-1 activity contributes to increased cardiovascular events in the elderly population.