Structures of the human dopamine D3 receptor-Gi complexes.

The dopamine system, including five dopamine receptors (D1R-D5R), plays essential roles in the central nervous system (CNS), and ligands that activate dopamine receptors have been used to treat many neuropsychiatric disorders. Here, we report two cryo-EM structures of human D3R in complex with an inhibitory G protein and bound to the D3R-selective agonists PD128907 and pramipexole, the latter of which is used to treat patients with Parkinson's disease. The structures reveal agonist binding modes distinct from the antagonist-bound D3R structure and conformational signatures for ligand-induced receptor activation. Mutagenesis and homology modeling illuminate determinants of ligand specificity across dopamine receptors and the mechanisms for Gi protein coupling. Collectively our work reveals the basis of agonist binding and ligand-induced receptor activation and provides structural templates for designing specific ligands to treat CNS diseases targeting the dopaminergic system.

A Randomized Phase 3 Study Comparing P2B001 to its Components (Low-Dose Extended-Release Rasagiline and Pramipexole) and to Optimized Doses of Marketed Extended-Release Pramipexole in Early Parkinson's Disease.

BACKGROUND: There remains uncertainty as to the optimal way to initiate therapy for Parkinson's disease (PD) to maximize benefit and minimize adversity. OBJECTIVES: The objective was to determine if P2B001 (a fixed, low-dose, extended-release [ER] combination of pramipexole 0.6 mg and rasagiline 0.75 mg) is superior to each of its components and compare its safety and efficacy to optimized treatment with marketed doses of pramipexole-ER. METHODS: This was a 12-week, double-blind study (NCT03329508). Total of 544 untreated patients with PD were randomized (2:2:2:1) to treatment with P2B001, its individual components (pramipexole-ER 0.6 mg or rasagiline-ER 0.75 mg), or commercial doses of pramipexole-ER titrated to optimal dose (1.5-4.5 mg). The primary endpoint was change from baseline to week 12 in Unified Parkinson's Disease Rating Scale (UPDRS) parts II and III. The key secondary endpoint was the change from baseline in the Epworth Sleepiness Scale (ESS) for P2B001 versus the titrated dose of pramipexole-ER. RESULTS: P2B001 provided superior efficacy compared to each of its components; mean (95% CI) treatment differences in UPDRS II + III scores were -2.66 (95% CI, -4.33 to -1.00) versus pramipexole-ER 0.6 mg (P = 0.0018) and - 3.30 (95% CI, -4.96 to -1.63) versus rasagiline-ER 0.75 mg (P < 0.0001). P2B001 had comparable efficacy with the titrated dose of pramipexole-ER (mean, 3.2 mg), but significantly less worsening in daytime-sleepiness (ESS treatment difference: -2.66 [95% CI, -3.50 to -1.81]; P < 0.0001). P2B001 was well-tolerated with fewer sleep-related and dopaminergic adverse events than titrated doses of pramipexole-ER including somnolence, orthostatic hypotension, and neuropsychiatric side effects. CONCLUSIONS: P2B001 had superior efficacy to its individual components and was comparable with commercially used doses of pramipexole-ER with less worsening of sleepiness and fewer dopaminergic adverse events. These findings support considering once-daily P2B001 as initial therapy for patients with early PD. © 2023 International Parkinson and Movement Disorder Society.

Transdermal Delivery of Pramipexole Using Microneedle Technology for the Potential Treatment of Parkinson's Disease.

Parkinson's disease (PD) is a debilitating neurodegenerative disease primarily impacting neurons responsible for dopamine production within the brain. Pramipexole (PRA) is a dopamine agonist that is currently available in tablet form. However, individuals with PD commonly encounter difficulties with swallowing and gastrointestinal motility, making oral formulations less preferable. Microneedle (MN) patches represent innovative transdermal drug delivery devices capable of enhancing skin permeability through the creation of microconduits on the surface of the skin. MNs effectively reduce the barrier function of skin and facilitate the permeation of drugs. The work described here focuses on the development of polymeric MN systems designed to enhance the transdermal delivery of PRA. PRA was formulated into both dissolving MNs (DMNs) and directly compressed tablets (DCTs) to be used in conjunction with hydrogel-forming MNs (HFMNs). In vivo investigations using a Sprague-Dawley rat model examined, for the first time, if it was beneficial to prolong the application of DMNs and HFMNs beyond 24 h. Half of the patches in the MN cohorts were left in place for 24 h, whereas the other half remained in place for 5 days. Throughout the entire 5 day study, PRA plasma levels were monitored for all cohorts. This study confirmed the successful delivery of PRA from DMNs (Cmax = 511.00 ± 277.24 ng/mL, Tmax = 4 h) and HFMNs (Cmax = 328.30 ± 98.04 ng/mL, Tmax = 24 h). Notably, both types of MNs achieved sustained PRA plasma levels over a 5 day period. In contrast, following oral administration, PRA remained detectable in plasma for only 48 h, achieving a Cmax of 159.32 ± 113.43 ng/mL at 2 h. The HFMN that remained in place for 5 days demonstrated the most promising performance among all investigated formulations. Although in the early stages of development, the findings reported here offer a hopeful alternative to orally administered PRA. The sustained plasma profile observed here has the potential to reduce the frequency of PRA administration, potentially enhancing patient compliance and ultimately improving their quality of life. This work provides substantial evidence advocating the development of polymeric MN-mediated drug delivery systems to include sustained plasma levels of hydrophilic pharmaceuticals.

Dopamine agonists in the treatment of Parkinson's disease: the show must go on.

Dopamine agonists (DA) have proven very successful in the treatment of Parkinson's disease for a good many years now. In the 1990's they experienced a high level of acceptance particularly in the European countries because their efficacy was in fact established, their tolerability was improved on and, in addition, several preparations were available with longer effect durations. But the discovery of cardiac fibroses led to a substantial setback and even rejection of therapy using ergoline DA. In recent years, impulse control disturbances have been observed increasingly with the result that higher doses have been reduced and the previously popular use of non-ergoline DA was discontinued. In addition, newer data on levodopa were published which clearly relativized the occurrence of late complications under levodopa and led to a differentiated use. Thus the importance of their use has waned over the years. But we should rather avoid repeating the mistakes of the past. DA serve us well and reliably so. The pendulum apparently thrives of the extremes but in the case of DA we should keep from falling back into the other extreme: We can and in fact must further make use of the DA, but with a clear view of specific goals and in a differentiated way. DA constitute the second-most important substance class after levodopa. Their optimized application can only be recommended for the good of our patients.

The bioenergetics of traumatic brain injury and its long-term impact for brain plasticity and function.

Mitochondria provide the energy to keep cells alive and functioning and they have the capacity to influence highly complex molecular events. Mitochondria are essential to maintain cellular energy homeostasis that determines the course of neurological disorders, including traumatic brain injury (TBI). Various aspects of mitochondria metabolism such as autophagy can have long-term consequences for brain function and plasticity. In turn, mitochondria bioenergetics can impinge on molecular events associated with epigenetic modifications of DNA, which can extend cellular memory for a long time. Mitochondrial dysfunction leads to pathological manifestations such as oxidative stress, inflammation, and calcium imbalance that threaten brain plasticity and function. Hence, targeting mitochondrial function may have great potential to lessen the outcomes of TBI.

Impulse control disorders in Parkinson's disease patients treated with pramipexole and ropinirole: a systematic review and meta-analysis.

BACKGROUND: This analysis is the first systematic review and meta-analysis assessing occurrences of ICD in PD patients treated with oral DAs: ropinirole (ROP) and pramipexole (PRX). This study compares the two oral DAs to a transdermal patch, rotigotine (RTG). METHODS: We performed an extensive systematic search for eligible studies from PubMed, Embase, Cochrane Library, and Google Scholar. The data was analyzed by various software, including EndNote, Rayyan, PRISM, and RevMan. Two studies incorporating 658 patients collectively were assessed. RESULTS: This meta-analysis shows a significant correlation between the usage of PRX (25.3%) or ROP (21.8%) and the development of ICD in PD patients. Compared to the transdermal patch, RTG, PRX was found to have a significant relative risk (P < 0.0001) of 3.46 (95% CI 2.07-5.76), and ROP was found to have a significant relative risk (P < 0.0001) of 2.98 (95% CI 1.77-5.02). The data collected shows RTG is approximately three times less likely to cause ICDs than oral PRX and ROP. CONCLUSION: The present investigation provides insight into ICD occurrences with PRX, ROP, and RTG to allow physicians to make more informed decisions on risk versus reward when deciding how to treat a PD patient with these drugs. However, related to various disclosed limitations, our conclusion cannot provide definitive practice protocols.

Impulse control disorders in Parkinson's disease: a retrospective analysis of 1824 patients in a 12-year period.

OBJECTIVE: This study aims to clinically evaluate the impulse control disorders (ICDs) encountered in treating Parkinson's disease. METHOD: This is a retrospective analysis between 2010 and 2022. We retrieved the medical records of all patients diagnosed with idiopathic Parkinson's disease. The demographic and clinical findings were recorded. ICDs constituted a specific item in the examination, and each one (compulsive shopping, compulsive eating, pathological gambling, hypersexuality, punding, dopamine dysregulation syndrome, and hobbyism) was noted separately. RESULTS: In the study period, we identified 1824 patients (56.2% men, n = 1025). The mean age was 70.5 ± 11.9 years. In the cohort, 128 (7%) patients with Parkinson's disease had one or more ICDs. The ICDs were compulsive shopping, punding/hobbyism, compulsive eating, hypersexuality, pathological gambling, and dopamine dysregulation syndrome. When we compared patients with and without ICDs, patients with ICDs were younger (p ≤ 0.001), and the men/women ratio was higher in this group with ICDs. Although the mean daily pramipexole dose was higher in patients with ICDs, mean daily long-acting pramipexole dose was only 1.4 ± 0.92 mg/day. CONCLUSION: The significant findings in this study were (i) the lower frequency of ICDs (7%); (ii) the common occurrence of compulsive shopping, punding/hobbyism, and compulsive eating; and (iii) the development of ICDs under relatively lower doses of pramipexole. We suggest that ICDs in Parkinson's disease should be associated with a personal trait with dopamine agonists, and potential electrophysiological or genetic markers of this trait warrant further analysis to avoid treatment in these patients.

In vitro drug screening models derived from different PC12 cell lines for exploring Parkinson's disease based on electrochemical signals of catecholamine neurotransmitters.

Gold nanostructures and a Nafion modified screen-printed carbon electrode (Nafion/AuNS/SPCE) were developed to assess the cell viability of Parkinson's disease (PD) cell models. The electrochemical measurement of cell viability was reflected by catecholamine neurotransmitter (represented by dopamine) secretion capacity, followed by a traditional tetrazolium-based colorimetric assay for confirmation. Due to the  capacity to synthesize, store, and release catecholamines as well as their unlimited homogeneous proliferation, and ease of manipulation, pheochromocytoma (PC12) cells were used for PD cell modeling. Commercial low-differentiated and highly-differentiated PC12 cells, and home-made nerve growth factor (NGF) induced low-differentiated PC12 cells (NGF-differentiated PC12 cells) were included in the modeling. This approach achieved sensitive and rapid determination of cellular modeling and intervention states. Notably, among the three cell lines, NGF-differentiated PC12 cells displayed the enhanced neurotransmitter secretion level accompanied with attenuated growth rate, incremental dendrites in number and length that were highly resemble with neurons. Therefore, it was selected as the PD-tailorable modeling cell line. In short, the electrochemical sensor can be used to sensitively determine the biological function of neuron-like PC12 cells with negligible destruction and to explore the protective and regenerative impact of various substances on nerve cell model.

Pramipexole Hyperactivates the External Globus Pallidus and Impairs Decision-Making in a Mouse Model of Parkinson's Disease.

In patients with Parkinson's disease (PD), dopamine replacement therapy with dopamine D2/D3 receptor agonists induces impairments in decision-making, including pathological gambling. The neurobiological mechanisms underlying these adverse effects remain elusive. Here, in a mouse model of PD, we investigated the effects of the dopamine D3 receptor (D3R)-preferring agonist pramipexole (PPX) on decision-making. PD model mice were generated using a bilateral injection of the toxin 6-hydroxydopamine into the dorsolateral striatum. Subsequent treatment with PPX increased disadvantageous choices characterized by a high-risk/high-reward in the touchscreen-based Iowa Gambling Task. This effect was blocked by treatment with the selective D3R antagonist PG-01037. In model mice treated with PPX, the number of c-Fos-positive cells was increased in the external globus pallidus (GPe), indicating dysregulation of the indirect pathway in the corticothalamic-basal ganglia circuitry. In accordance, chemogenetic inhibition of the GPe restored normal c-Fos activation and rescued PPX-induced disadvantageous choices. These findings demonstrate that the hyperactivation of GPe neurons in the indirect pathway impairs decision-making in PD model mice. The results provide a candidate mechanism and therapeutic target for pathological gambling observed during D2/D3 receptor pharmacotherapy in PD patients.

Neural and molecular investigation into the paraventricular thalamic-nucleus accumbens circuit for pain sensation and non-opioid analgesia.

The paucity of medications with novel mechanisms for pain treatment combined with the severe adverse effects of opioid analgesics has led to an imperative pursuit of non-opioid analgesia and a better understanding of pain mechanisms. Here, we identify the putative glutamatergic inputs from the paraventricular thalamic nucleus to the nucleus accumbens (PVTGlut→NAc) as a novel neural circuit for pain sensation and non-opioid analgesia. Our in vivo fiber photometry and in vitro electrophysiology experiments found that PVTGlut→NAc neuronal activity increased in response to acute thermal/mechanical stimuli and persistent inflammatory pain. Direct optogenetic activation of these neurons in the PVT or their terminals in the NAc induced pain-like behaviors. Conversely, inhibition of PVTGlut→NAc neurons or their NAc terminals exhibited a potent analgesic effect in both naïve and pathological pain mice, which could not be prevented by pretreatment of naloxone, an opioid receptor antagonist. Anterograde trans-synaptic optogenetic experiments consistently demonstrated that the PVTGlut→NAc circuit bi-directionally modulates pain behaviors. Furthermore, circuit-specific molecular profiling and pharmacological studies revealed dopamine receptor 3 as a candidate target for pain modulation and non-opioid analgesic development. Taken together, these findings provide a previously unknown neural circuit for pain sensation and non-opioid analgesia and a valuable molecular target for developing future safer medication.

Restless legs syndrome in DNAJC12 deficiency.

BACKGROUND: Restless legs syndrome (RLS) is characterized by an unpleasant or painful sensation generally localized to lower limbs and relieved by movement. Its pathogenesis is hypothesized to involve the dopaminergic system, also in the light of the response of RLS to ex adiuvantibus treatment with dopamine agonists. DNAJC12 deficiency is a recently identified inherited metabolic disease coupling hyperphenylalaninemia to deficient dopaminergic and serotoninergic neurotransmission, due to the combined impairment of the three aromatic amino acids' (i.e., phenylalanine, tyrosine, and tryptophan) hydroxylases. DNAJC12 deficiency was reported in 43 patients so far, presenting with wide spectrum of clinical symptoms. CASE PRESENTATION RESULTS: Here, we report RLS as a novel clinical manifestation of DNAJC12 deficiency, occurring in two adults while on treatment with L-dopa at longitudinal follow-up. The adjunct of low-dose pramipexole was effective in both patients to treat RLS. Besides, this treatment also allowed an improvement of dopaminergic homeostasis, as evidenced by clinical amelioration and stabilization of a peripheral short prolactin profile (a tool to indirectly evaluate dopaminergic homeostasis). DISCUSSION: Besides including RLS as a new treatable clinical manifestation of DNAJC12, these observations may suggest the opportunity of a selective screening for DNAJC12 deficiency in patients with idiopathic RLS.

Effects of different doses of dopamine receptor agonist pramipexole on neurobehaviors and changes of mitochondrial membrane potentials in rats with global cerebral ischemia-reperfusion injury.

OBJECTIVE: To explore the effects of different doses of dopamine receptor agonist pramipexole on neurobehaviors and changes of mitochondrial membrane potential in rats with global cerebral ischemia-reperfusion injury. METHODS: A total of 75 SPF Sprague-Dawley male rats were randomly divided into sham group (n=20), model group (n=20), pramipexole administration group (n=35). The rat model of global cerebral ischemia-reperfusion injury was prepared by the modified Pulsinelli's four-vessel occlusion method. Pramipexole administration group was administered intraperitoneally in rats with global cerebral ischemia-reperfusion injury at different doses of pramipexole 0.25 mg/kg, 0.5 mg/kg, 1 mg/kg, 2 mg/kg, once a day for 14 consecutive days. Based on the results of modified neurological severity scores, open field test and morphology by Nissl's staining to determine the optimal dose of pramipexole. Mitochondrial membrane potential in the optimal dose of pramipexole administration group were measured by the JC-1 fluorescent probe staining method. RESULTS: 1. Different doses of pramipexole 0.25 mg/kg, 0.5 mg/kg, 1 mg/kg, and 2 mg/kg, were used as drug administration in rats with global cerebral ischemia-reperfusion injury for 14 consecutive days, and we found that all four doses of pramipexole could improve the modified neurological severity scores of rats with global cerebral ischemia-reperfusion injury to varying degrees, but only 0.5 mg/kg pramipexole at 1, 3, 7 and 14 days consistently reduced modified neurological severity scores and improved neurological function in rats with global cerebral ischemia-reperfusion injury. In the open-field test, only 0.5 mg/kg pramipexole increased the number of entries into the central zone, duration spent in the central zone, total distance travelled in the open field and average velocity, which improved the spontaneous activities and reduced anxiety and depression of rats with global cerebral ischemia-reperfusion injury. 2. Different doses of pramipexole 0.25 mg/kg, 0.5 mg/kg, 1 mg/kg, and 2 mg/kg for 14 consecutive days significantly increased the number of surviving neurons in the hippocampal CA1 subfield in rats with global cerebral ischemia-reperfusion injury to varying degrees. Based on these results, we tentatively found that 0.5 mg/kg pramipexole may be the optimal dose in all of the above. 3. We found that 0.5 mg/kg pramipexole significantly increased the mitochondrial membrane potential in rats after global cerebral ischemia-reperfusion injury. CONCLUSION: Different doses of dopamine receptor agonist pramipexole improved neurological function of rats with global cerebral ischemia-reperfusion injury to varying degrees, and 0.5 mg/kg pramipexole may be the optimal dose in all of the above. Pramipexole may produce neuroprotective effects by protecting neurons in the hippocampus and improving the mitochondrial membrane potential after global cerebral ischemia-reperfusion injury.

Zishen pingchan granules combined with pramipexole in the improvement of depressive symptoms in Parkinson's disease: a prospective, multicenter, randomized, double-blind, controlled clinical study.

BACKGROUND AND OBJECTIVE: Zishen Pingchan granule (ZPG), a traditional Chinese herbal recipe for treating Parkinson's disease (PD), is usually used as an add-on drug with some antiparkinsonian drugs in China. The objectives of this study were to evaluate the efficacy, safety, and tolerability of ZPG combined with pramipexole in the treatment of depression in PD (dPD). METHODS: A 12-week, multicenter, randomized, double-blind, and placebo-controlled study on ZPG was performed on a total of 200 patients who were treated with pramipexole but still had mild to moderate depressive symptoms. Patients were randomly divided into ZPG (n = 100) or placebo (n = 100). The primary effective result was the mean change from the baseline on the Hamilton Depression Scale 17 items (HAM-D-17) over 12 weeks and the clinical efficacy rate. Secondary endpoints were the mean change from the baseline in the Geriatric Depression Scale (GDS-15), Unified Parkinson's disease rating scale Part III (UPDRS III), Parkinson's quality of life scale (PDQ-8), and Parkinson's disease sleep scale (PDSS-2) over 12 weeks. RESULTS: After 12 weeks of treatment, ZPG significantly reduced the mean [95% confidence interval] HAMD score vs. placebo (- 1.43 scores [- 2.50, - 0.36]; p = 0.009). The clinical remission rate and responders of the ZPG group were higher than those of the placebo (46.1% vs. 31.0%; p = 0.041; 34.8% vs. 18.4%; p = 0.014). A significant improvement in the PDSS-2 score was also observed in the ZPG group compared with that in the placebo group (- 3.56 scores [- 5.77, - 1.35]; p = 0.002). A total of 7 patients (7.1%) in the ZPG group had mild adverse events (AEs) vs 9 patients (9%) in the placebo group. No severe AEs were observed in either group. The randomization and controlled clinical study revealed that ZPG was effective, safe, and well-tolerated. CONCLUSION: ZPG combined with pramipexole further reduced the depressive symptoms and improved the sleeping quality of PD patients. Trial registration The protocol was retrospectively registered at the Chinese Clinical Trial Registry, Unique identifier: ChiCTR1800019942, date of registration: December 9, 2018; http://www.chictr.org.cn/showproj.aspx?proj=30432.

Enhanced Taste Recognition Following Subacute Treatment With The Dopamine D2/D3 Receptor Agonist Pramipexole in Healthy Volunteers.

BACKGROUND: Patients with Parkinson's disease (PD) show impaired performance in taste recognition tests, which suggests a possible dopaminergic influence on gustatory functioning. To experimentally test this hypothesis, we assessed whether pharmacological manipulation of dopaminergic signaling in healthy volunteers can affect performance in a standardized taste recognition test. METHODS: Physically and mentally healthy volunteers (n = 40, age 18-43 years) were randomly allocated to treatment with either pramipexole or placebo using a double-blind, parallel-group design. After 12 to 15 days of treatment (dose titrated up from 0.25 mg/d of pramipexole salt to 1.0 mg/d), taste recognition performance was assessed using a standardized and validated assay (taste strip test). Additionally, visual analogue scale ratings of subjective pleasantness and disgustingness of taste samples were obtained. RESULTS: Compared with the placebo group, participants receiving pramipexole showed significantly higher total recognition accuracy (medianpramipexole = 14.0, medianplacebo = 13.0, U = 264.5, P = .04). This was driven by a higher sensitivity for taste in the pramipexole group. Exploratory analysis of pleasantness and disgustingness ratings of appetitive (sweet) vs aversive (bitter) stimuli suggested that pramipexole treatment was associated with overall blunted hedonic responses, but this effect did not survive the inclusion of nausea (a side effect of treatment) as a covariate in the analysis. CONCLUSIONS: Healthy volunteers who received subacute pramipexole treatment exhibited higher taste recognition performance compared with the placebo group. This finding is consistent with a proposed role of the dopaminergic system in gustatory functioning and could have important theoretical and clinical implications.

D2/D3 Receptor Agonism: Paving the Way for a New Therapeutic Target for Taste Disorders in Parkinson's Disease and Other Conditions?

Chemosensory (i.e., olfaction and taste) dysfunction is common in neurodegenerative (e.g., Parkinson's disease, Alzheimer's disease, and dementia), psychiatric (e.g., depression, bipolar disorders, other conditions), and postinfectious (i.e., long COVID) diseases and in the elderly. Despite its impact on patients' quality of life, no established treatment for taste disorders exists so far. A recent report on the effect of pramipexole, a D2/D3 agonist, on taste performance in healthy participants provides support for a new potential therapeutic target for taste dysfunction to be tested in future randomized, placebo-controlled, clinical trials across several populations reporting gustatory symptoms.

G-protein biased signaling agonists of Dopamine D3 receptor promote distinct activation patterns of ERK1/2.

Dopamine D3 receptors (D3R) have a causal role in neurological and psychiatric disorders. We have developed a novel class of G-protein biased (GPB) signaling D3R agonists with minimal ß-arrestin2 (ßarr2) recruitment and demonstrated efficacy in rodent model of Parkinson's disease. This contrasts with unbiased (UB) D3R agonists like Pramipexole which recruit both ß-arrestin and G-proteins for signaling. In this study, we investigated the effects of GPB and UB agonists on D3R mediated activation of mono and dual phosphorylation of ERK1/2. We used the neuronal-like SH-SY5Y cells stably expressing D3R and ßarr2 knockdown (ßarr2KD) to delineate the roles of Gi/o and ßarr2 on phosphorylation patterns of ERK1/2 induced by D3R agonists. Results indicate GPB and UB agonists promote similar early and late phase mono activation patterns of ERK1/2. On the contrary, GPB and UB agonists promote either early or early and late phase dual activation of ERK1/2, respectively. The early phase dual activation of ERK1/2 is predominantly promoted by Gi/o while the late phase dual activation by ßarr2 recruitment. PKC plays a significant role in both the early and late phase dual phosphorylation of ERK1/2. ßarr2KD significantly increased short- and long-term dual phosphorylation levels of ERK1/2 induced by GPB agonists which was inhibited by a combination of Gi/o and PKC inhibitors. Interestingly, ßarr2KD significantly reduced the short and long-term dual phosphorylation of ERK1/2 by UB agonists. Overall, this study highlights that biased signaling agonists of D3R have differential effects on ERK1/2 which may be advantageous to develop better drugs.

Pharmacological targeting of G protein-coupled receptor heteromers.

A main rationale for the role of G protein-coupled receptor (GPCR) heteromers as targets for drug development is the putative ability of selective ligands for specific GPCRs to change their pharmacological properties upon GPCR heteromerization. The present study provides a proof of concept for this rationale by demonstrating that heteromerization of dopamine D1 and D3 receptors (D1R and D3R) influences the pharmacological properties of three structurally similar selective dopamine D3R ligands, the phenylpiperazine derivatives PG01042, PG01037 and VK4-116. By using D1R-D3R heteromer-disrupting peptides, it could be demonstrated that the three D3R ligands display different D1R-D3R heteromer-dependent pharmacological properties: PG01042, acting as G protein-biased agonist, counteracted D1R-mediated signaling in the D1R-D3R heteromer; PG01037, acting as a D3R antagonist cross-antagonized D1R-mediated signaling in the D1R-D3R heteromer; and VK4-116 specifically acted as a ß-arrestin-biased agonist in the D1R-D3R heteromer. Molecular dynamics simulations predicted potential molecular mechanisms mediating these qualitatively different pharmacological properties of the selective D3R ligands that are dependent on D1R-D3R heteromerization. The results of in vitro experiments were paralleled by qualitatively different pharmacological properties of the D3R ligands in vivo. The results supported the involvement of D1R-D3R heteromers in the locomotor activation by D1R agonists in reserpinized mice and L-DOPA-induced dyskinesia in rats, highlighting the D1R-D3R heteromer as a main pharmacological target for L-DOPA-induced dyskinesia in Parkinson's disease. More generally, the present study implies that when suspecting its pathogenetic role, a GPCR heteromer, and not its individual GPCR units, should be considered as main target for drug development.

Efficacy of pramipexole on quality of life in patients with Parkinson's disease: a systematic review and meta-analysis.

BACKGROUND: Quality of life (QoL) in patients with Parkinson's disease (PD) is increasingly used as an efficacy outcome in clinical studies of PD to evaluate the impact of treatment from the patient's perspective. Studies demonstrating the treatment effect of pramipexole on QoL remain inconclusive. This study aims to evaluate the effect of pramipexole on QoL in patients with PD by conducting a systematic review and meta-analysis of existing clinical trials. METHODS: A systematic literature search of PubMed, Embase and the Cochrane Library was performed from inception to 30 April 2022 to identify randomised, placebo-controlled trials of patients with idiopathic PD receiving pramipexole, who reported a change from baseline in their QoL as measured by the 39-item Parkinson's Disease Questionnaire (PDQ-39). Risk of bias was independently assessed by two reviewers using the Cochrane Collaboration's tool for bias assessment. RESULTS: Of 80 eligible articles screened, six trials consisting of at least 2000 patients with early or advanced PD were included. From the synthesis of all six selected trials, a significant mean change from baseline in the PDQ-39 total score of -2.49 (95% CI, -3.43 to -1.54; p < 0.0001) was observed with pramipexole compared with placebo. A trend toward improvement in QoL was consistently observed among patients who received optimal doses of pramipexole (≥ 80% of the study population on 1.5 mg dosage), regardless of disease severity (advanced versus early) or baseline QoL levels. CONCLUSION: This meta-analysis provides evidence for the potential treatment benefit of pramipexole in improving QoL in patients with PD.

Parkinson's disease is a chronic, progressive nervous system disorder with no known cure. Patients may experience a number of symptoms including stiffness, slowness, and uncontrollable muscle movements, all of which impact their quality of life. Most clinical studies in Parkinson's disease measure the effect of treatment on improving symptoms, but other aspects such as quality of life are often overlooked. It is important to include quality of life measures in clinical studies of Parkinson's disease, such as the 39-item Parkinson's disease questionnaire (PDQ-39), to understand the impact of treatment from patients' perspectives. Pramipexole is a dopamine agonist that is well-tolerated and effective at treating Parkinson's disease symptoms. However, studies examining its effect on quality of life are inconclusive. This meta-analysis of existing clinical trials therefore aimed to evaluate the effect of pramipexole on quality of life in patients with Parkinson's disease. Six trials consisting of at least 2000 patients with early or advanced Parkinson's disease receiving treatment with pramipexole were included in this meta-analysis. Analysis of these six trials found a significant improvement in PDQ-39 total score with pramipexole compared with placebo. This meta-analysis provides new evidence for the potential treatment benefit of pramipexole in improving quality of life in patients with Parkinson's disease.

Reorienting of pramipexole as a promising therapy for acute pancreatitis in a rat model by suppressing TLR4\NF-κB p65\NLRP3 inflammasome signaling.

Acute pancreatitis (AP), a disorder of global importance, has a growing incidence and prevalence, particularly in the Western world. Its complications include pseudocysts and chronic pancreatitis. Pramipexole (PMX), a D2/3 receptor selecting agonist used in Parkinsonism, was reported to have anti-inflammatory effects. This study explored the potential curative role of PMX in an l-arginine-induced acute pancreatitis rat model in addition to a possible mechanistic pathway. Rats were divided randomly into three groups: control, l-arginine, and l-arginine + PMX. Seven days after AP induction, rats were decapitated and estimated for serum amylase, lipase, glucose, pancreatic inflammatory mediators toll-like receptor-4, nuclear factor κ B p65, serum tumor necrosis factor-α, NOD-, LRR and pyrin domain- containing protein 3 (NLRP3) inflammasome, caspase-1, interleukin 1ß, oxidative biomarkers malondialdehyde, myeloperoxidase, nitrite/nitrate, reduced glutathione, and the apoptotic marker caspase-3, with pancreatic histopathological changes. l-arginine-mediated AP was proved by elevated serum lipase and amylase and pancreatic inflammatory, oxidative, and apoptotic markers with infiltration of inflammatory cells using hematoxylin and eosin stain. PMX improved all these adverse signs of AP greatly. PMX might be considered an innovative therapy for AP due to its remarkable antioxidant, antiapoptotic, and anti-inflammatory effects, which are attributed to the suppression of the NLRP3 inflammasome and its downstream inflammatory cytokines.

Augmentation in patients with restless legs syndrome receiving pramipexole therapy: a retrospective study in a single center from China.

PURPOSE: Augmentation is a major complication of long-term pramipexole treatment of restless legs syndrome (RLS). However, there have been no studies on augmentation in Chinese patients with RLS. We therefore investigated the clinical characteristics of augmentation in RLS patients treated with pramipexole in a real-world Chinese setting. METHODS: This study was an observational, retrospective assessment of 103 patients with RLS, who had been continuously treated with pramipexole for at least one month between January 2016 and December 2018 in a tertiary hospital in East China. Demographic data and disease and drug treatment information were collected from electronic medical records and telephone interviews to analyze the rate and clinical features of augmentation. Augmentation was confirmed by Max Planck Institute criteria. Comparisons were made between patients with and without augmentation. RESULTS: Fifteen patients (15%) were classified as having augmentation. Compared to RLS patients without augmentation, more patients with augmentation switched from other dopaminergic drugs (P<0.05) and had a longer duration of RLS symptoms before pramipexole treatment (P<0.05). In addition, patients with augmentation had a longer duration (P<0.05) and higher dosage (P<0.05) of pramipexole than those without augmentation. Augmentation was possibly associated with pramipexole tolerance (P<0.01). CONCLUSION: The augmentation rate of the Chinese RLS patients in our study was 15%. Augmentation may be associated with switching from other dopaminergic drugs, long disease duration before pramipexole use, the dose and duration of pramipexole, and tolerance to pramipexole.