Managing autonomic dysfunction in Parkinson's disease: a review of emerging drugs

The Ubiquitin Proteasome System as a Therapeutic Area in Parkinson's Disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder. There are no available therapeutics that slow or halt the progressive loss of dopamine-producing neurons, which underlies the primary clinical symptoms. Currently approved PD drugs can provide symptomatic relief by increasing brain dopamine content or activity; however, the alleviation is temporary, and the effectiveness diminishes with the inevitable progression of neurodegeneration. Discovery and development of disease-modifying neuroprotective therapies has been hampered by insufficient understanding of the root cause of PD-related neurodegeneration. The etiology of PD involves a combination of genetic and environmental factors. Although a single cause has yet to emerge, genetic, cell biological and neuropathological evidence implicates mitochondrial dysfunction and protein aggregation. Postmortem PD brains show pathognomonic Lewy body intraneuronal inclusions composed of aggregated α-synuclein, indicative of failure to degrade misfolded protein. Mutations in the genes that code for α-synuclein, as well as the E3 ubiquitin ligase Parkin, cause rare inherited forms of PD. While many ubiquitin ligases label proteins with ubiquitin chains to mark proteins for degradation by the proteasome, Parkin has been shown to mark dysfunctional mitochondria for degradation by mitophagy. The ubiquitin proteasome system participates in several aspects of the cell's response to mitochondrial damage, affording numerous therapeutic opportunities to augment mitophagy and potentially stop PD progression. This review examines the role and therapeutic potential of such UPS modulators, exemplified by both ubiquitinating and deubiquitinating enzymes.

Advances in the Therapeutic Use of Non-Ergot Dopamine Agonists in the Treatment of Motor and Non-Motor Symptoms of Parkinson's Disease

Dopamine (DA) agonists, as an excellent dopamine replacement therapy for patients with early and advanced Parkinson's disease (PD), play a vital role in controlling motor and several nonmotor symptoms. Besides, the application of DA agonists may delay levodopa therapy and the associated risk of motor complications. Indeed, each DA agonist has unique pharmacokinetic and pharmacodynamic characteristics and therefore has different therapeutic efficacy and safety profile. The comorbidities, significant non-motor manifestations, concomitant medications, and clinical features of PD individuals should guide the selection of a specific DA agonist to provide a more patient-tailored treatment option. Thorough knowledge of DA agonists helps clinicians better balance clinical efficacy and side effects. Therefore, this review refers to recent English-written articles on DA agonist therapy for PD patients and summarizes the latest findings on non-ergot DA agonists as well as the advantages and disadvantages of each compound to help clinicians in the selection of a specific DA agonist. In addition, novel D1/D5 partial agonists and new formulations of DA agonists are also discussed.

Neurotrophic effects of Botulinum neurotoxin type A in hippocampal neurons involve activation of Rac1 by the non-catalytic heavy chain (HCC/A)

Botulinum neurotoxins (BoNTs) are extremely potent naturally occurring poisons that act by silencing neurotransmission. Intriguingly, in addition to preventing presynaptic vesicle fusion, BoNT serotype A (BoNT/A) can also promote axonal regeneration in preclinical models. Here we report that the non-toxic C-terminal region of the receptor-binding domain of heavy chain BoNT/A (HCC/A) activates the small GTPase Rac1 and ERK pathway to potentiate axonal outgrowth, dendritic protrusion formation and synaptic vesicle release in hippocampal neurons. These data are consistent with HCC/A exerting neurotrophic properties, at least in part, independent of any BoNT catalytic activity or toxic effect.

Therapeutic Applications of Botulinum Neurotoxin for Autonomic Symptoms in Parkinson's Disease: An Updated Review

Parkinson's disease is the most common age-related motoric neurodegenerative disease. In addition to the cardinal motor symptoms of tremor, rigidity, bradykinesia, and postural instability, there are numerous non-motor symptoms as well. Among the non-motor symptoms, autonomic nervous system dysfunction is common. Autonomic symptoms associated with Parkinson's disease include sialorrhea, hyperhidrosis, gastrointestinal dysfunction, and urinary dysfunction. Botulinum neurotoxin has been shown to potentially improve these autonomic symptoms. In this review, the varied uses of botulinum neurotoxin for autonomic dysfunction in Parkinson's disease are discussed. This review also includes discussion of some additional indications for the use of botulinum neurotoxin in Parkinson's disease, including pain.

Clinical features and relative factors of constipation in a cohort of Chinese patients with Parkinson's disease

BACKGROUND

Constipation as a most common non-motor symptom of Parkinson's disease (PD), has a higher prevalence compared to the general population. The etiologies of constipation in PD are diverse. In addition to physical weakness and other factors of disease, the lifestyles and eating habits are also important factors. Therefore, the prevalence and influencing factors of constipation may vary among different populations.

AIM

To determine the prevalence of constipation and analyze relative factors in a cohort of Chinese patients with PD.

METHODS

All the patients diagnosed with PD according to the movement disorders society criteria were consecutively collected by a self-developed questionnaire. Rome III diagnostic criteria were used to assess functional constipation and Wexner score was used to estimate the severity of constipation. Non-motor symptoms (NMS) were assessed with the non-motor symptoms assessment scale (NMSS). Unified Parkinson's disease Rating Scale III (UPDRS III) was used to evaluate the severity of motor symptoms. The modified Hoehn-Yahr stage was used to evaluate the severity of PD. Cognitive function was assessed using Montreal cognitive assessment (MoCA). Depression and anxiety were rated with the Hamilton depression scale (HAMD) and the Hamilton anxiety scale (HAMA). Quality of life was assessed using the Parkinson’s disease Questionnaire-39 items (PDQ-39).

RESULTS

Of 166 patients enrolled, 87 (52.41%) were accompanied with constipation, and 30 (34.48%) experienced constipation for 6.30 ± 5.06 years before motor symptoms occurred. Age, Hoehn-Yahr stage, disease duration, levodopa medication times, incidence of motor complications, the scores of UPDRS total, UPDRS III, NMSS, HAMD, HAMA, and PDQ-39 in the constipation group were higher than those in the non-constipation group (P < 0.05), but there was no difference in the scores of MoCA, clinical types, or medications between the two groups (P > 0.05). There was a higher incidence of depression in patients with constipation (P < 0.05), but there were no difference in the incidence of anxiety and cognitive impairment between the two groups (P > 0.05). As Hoehn-Yahr stages increased, the severity of constipation increased (P < 0.05), but not the incidence of constipation (P > 0.05). Pearson correlation analysis showed that constipation was moderately positively correlated with age, Hoehn-Yahr stage, and scores of NMSS, UPDRS III, UPDRS total, PDQ-39, HAMD, and HAMA (r = 0.255, 0.172, 0.361, 0.194, 0.221, 0.237, 0.238, and 0.207, P < 0.05). Logistic regression analysis showed that only NMSS score was an independent risk factor for constipation (P < 0.001).

CONCLUSION

Our findings confirm that constipation has a relatively high frequency in patients with PD. PD patients with constipation have a higher incidence of depression, which leads to worse quality of life.

Parkinson's disease and skin

Parkinson's disease is associated with a variety of dermatologic disorders and the study of skin may provide insights into pathophysiological mechanisms underlying this common neurodegenerative disorder. Skin disorders in patients with Parkinson's disease can be divided into two major groups: 1) non-iatrogenic disorders, including melanoma, seborrheic dermatitis, sweating disorders, bullous pemphigoid, and rosacea, and 2) iatrogenic disorders related either to systemic side effects of antiparkinsonian medications or to the delivery system of antiparkinsonian therapy, including primarily carbidopa/levodopa, rotigotine and other dopamine agonists, amantadine, catechol-O-methyl transferase inhibitors, subcutaneous apomorphine, levodopa/carbidopa intestinal gel, and deep brain stimulation. Recent advances in our understanding of the role of α-synuclein in peripheral tissues, including the skin, and research based on induced pluripotent stem cells derived from skin fibroblasts have made skin an important target for the study of Parkinson's disease pathogenesis, drug discovery, novel stem cell therapies, and diagnostics.