Parkinson's Disease and the Heart: Studying Cardiac Metabolism in the 6-Hydroxydopamine Model

Parkinson's-disease (PD) is an incurable, age-related neurodegenerative disease, and its global prevalence of disability and death has increased exponentially. Although motor symptoms are the characteristic manifestations of PD, the clinical spectrum also contains a wide variety of non-motor symptoms, which are the main cause of disability and determinants of the decrease in a patient's quality of life. Noteworthy in this regard is the stress on the cardiac system that is often observed in the course of PD; however, its effects have not yet been adequately researched. Here, an untargeted metabolomics approach was used to assess changes in cardiac metabolism in the 6-hydroxydopamine model of PD. Beta-sitosterol, campesterol, cholesterol, monoacylglycerol, α-tocopherol, stearic acid, beta-glycerophosphoric acid, o-phosphoethanolamine, myo-inositol-1-phosphate, alanine, valine and allothreonine are the metabolites that significantly discriminate parkinsonian rats from sham counterparts. Upon analysis of the metabolic pathways with the aim of uncovering the main biological pathways involved in concentration patterns of cardiac metabolites, the biosynthesis of both phosphatidylethanolamine and phosphatidylcholine, the glucose-alanine cycle, glutathione metabolism and plasmalogen synthesis most adequately differentiated sham and parkinsonian rats. Our results reveal that both lipid and energy metabolism are particularly involved in changes in cardiac metabolism in PD. These results provide insight into cardiac metabolic signatures in PD and indicate potential targets for further investigation.

Propolis induces cardiac metabolism changes in 6-hydroxydopamine animal model: A dietary intervention as a potential cardioprotective approach in Parkinson’s disease

While there is sustained growth of the older population worldwide, ageing is a consistent risk factor for neurodegenerative diseases, such as Parkinson’s-disease (PD). Considered an emblematic movement disorder, PD comprises a miscellany of non-motor symptoms, for which effective management remains an unfulfilled need in clinical practice. Highlighted are the cardiovascular abnormalities, that cause significant burden in PD patients. Evidence suggests that key biological processes underlying PD pathophysiology can be modulated by diet-derived bioactive compounds, such as green propolis, a natural functional food with biological and pharmacological properties. The effects of propolis on cardiac affection associated to PD have received little coverage. In this study, a metabolomics approach and Positron Emission Tomography (PET) imaging were used to assess the metabolic response to diet supplementation with green propolis on heart outcomes of rats with Parkinsonism induced by 6-hydroxydopamine (6-OHDA rats). Untargeted metabolomics approach revealed four cardiac metabolites (2-hydroxybutyric acid, 3-hydroxybutyric acid, monoacylglycerol and alanine) that were significantly modified between animal groups (6-OHDA, 6-OHDA + Propolis and sham). Propolis-induced changes in the level of these cardiac metabolites suggest beneficial effects of diet intervention. From the metabolites affected, functional analysis identified changes in propanoate metabolism (a key carbohydrate metabolism related metabolic pathway), glucose-alanine cycle, protein and fatty acid biosynthesis, energy metabolism, glutathione metabolism and urea cycle. PET imaging detected higher glucose metabolism in the 17 areas of the left ventricle of all rats treated with propolis, substantially contrasting from those rats that did not consume propolis. Our results bring new insights into cardiac metabolic substrates and pathways involved in the mechanisms of the effects of propolis in experimental PD and provide potential novel targets for research in the quest for future therapeutic strategies.

Foot and mouth disease leader protease (Lbpro): Investigation of prime side specificity allows the synthesis of a potent inhibitor

Foot and mouth disease virus expresses its genetic information as a single polyprotein that is translated from the single-stranded RNA genome. Proteinases contained within the polyprotein then generate the mature viral proteins. The leader protease (Lb(pro)) performs the initial cleavage by freeing itself from the growing polypeptide chain; subsequently, Lb(pro) cleaves the two homologues of the host cell protein eukaryotic initiation factor 4G (eIF4G). We showed that Lb(pro) possesses specific binding sites at the non prime side from S(1) down to S(7) [Santos et al. (2009) Biochemistry, 48, 7948-7958]. Here, we demonstrate that Lb(pro) has high prime side specificity at least down to the S'(5) site. Lb(pro) is thus not only one of the smallest papain-like cysteine peptidases but also one of the most specific. It can still however cleave between both K↓G and G↓R pairs. We further determined the two-step irreversible inhibition (E + I ↔ EI→ E - I) kinetic parameters of two known irreversible epoxide-based inhibitors of cysteine proteinases, E64 and CA074 on Lb(pro) that show for the reversible step (E + I ↔ EI) K(i) = 3.4 μM and 11.6 μM, and for the irreversible step (EI→E-I) k(4) = 0.16 and 0.06 min(-1), respectively. Knowledge of the Lb(pro) specificity led us to extend E64 by addition of the dipeptide R-P. This compound, termed E64-R-P-NH(2), irreversibly inhibited Lb(pro) with a K(i) = 30 nM and k(4) = 0.01 min(-1) and can serve as the basis for design of specific inhibitors of FMDV replication.

Substrate specificity of recombinant dengue 2 virus NS2B-NS3 protease: Influence of natural and unnatural basic amino acids on hydrolysis of synthetic fluorescent substrates

A recombinant dengue 2 virus NS2B-NS3 protease (NS means non-structural virus protein) was compared with human furin for the capacity to process short peptide substrates corresponding to seven native substrate cleavage sites in the dengue viral polyprotein. Using fluorescence resonance energy transfer peptides to measure kinetics, the processing of these substrates was found to be selective for the Dengue protease. Substrates containing two or three basic amino acids (Arg or Lys) in tandem were found to be the best, with Abz-AKRRSQ-EDDnp being the most efficiently cleaved. The hydrolysis of dipeptide substrates Bz-X-Arg-MCA where X is a non-natural basic amino acid were also kinetically examined, the best substrates containing aliphatic basic amino acids. Our results indicated that proteolytic processing by dengue NS3 protease, tethered to its activating NS2B co-factor, was strongly inhibited by Ca2+ and kosmotropic salts of the Hofmeister's series, and significantly influenced by substrate modifications between S4 and S6'. Incorporation of basic non-natural amino acids in short peptide substrates had significant but differential effects on Km and k(cat), suggesting that further dissection of their influences on substrate affinity might enable the development of effective dengue protease inhibitors.