Rotigotine-loaded microspheres exerts the antinociceptive effect via central dopaminergic system

Effect of Dispersion Medium on Pharmacokinetic Profile of Rotigotine Crystalline Suspension following Subcutaneous Injection

Rotigotine (RTG) is prescribed as a once-daily transdermal patch for managing early Parkinson’s disease (PD), which presents issues such as skin irritation and poor patient adherence. Therefore, the aims of the present study were to formulate aqueous and oily vehicle-based RTG crystalline suspensions for prolonged delivery and to compare their pharmacokinetic profiles and the local behaviors of RTG crystals. RTG-loaded aqueous (AS) and oil suspensions (OS) were fabricated using bead-milling technology (100 mg/mL as RTG), employing carboxymethyl cellulose and sesame oil as suspending agent and oily vehicle, respectively. RTG AS and OS exhibited comparable physical properties in terms of particle size (about 800−900 nm), crystallinity, and dissolution profile, despite higher drug solubility in OS than AS (19.6 and 0.07 mg/mL, respectively). However, AS and OS exhibited markedly distinctive local distribution and inflammatory responses at the injection site, which further promoted different pharmacokinetic patterns following subcutaneous injection in rats. With OS, no drug aggregates were observed with prolonged persistence of the Sudan III-stained oily vehicle at the injection site. In contrast, with AS injection, drug clusters > 7 mm were formed, followed by an enclosure with macrophages and a fibroblastic band. Accordingly, AS exhibited a protracted pharmacokinetic profile over 3 weeks, with prolonged elimination half-life. The local inflammatory response caused by AS injection was almost alleviated after 3 weeks post-dosing. Based on these findings, we conclude that RTG AS system can be a platform to design sophisticated long-acting delivery systems with extended dosing intervals to manage PD.

Continuous Activation of Dopamine Receptors Alleviates LPS-Induced Liver Injury in Mice via β-arrestin2 Dependent Akt/NF-κB Pathway

Many studies showed that dopamine receptors (DRs) agonists have anti-inflammatory effects. Rotigotine, a non-ergot dopamine receptor agonist, mainly actives DRD2/DRD3/DRD1. Rotigotine extended-release microspheres (RoMS) are a sustained-release formulation that can release sustainably rotigotine for more than 7 days after a single dose of RoMS. This study aimed to investigate whether RoMS can attenuate the lipopolysaccharide (LPS)-induced liver injury of mice. The liver injury was evaluated by assaying serum transaminase and observing histopathological changes. The levels of pro-inflammatory cytokines in serum were also detected. Western blot was employed to assay the expression of proteins in the Akt/NF-κB pathway. The results showed that pre-administration with a single dose of RoMS could inhibit the increase of serum transaminase induced by LPS, alleviate the pathological damage of liver tissue, and decrease the levels of tumor necrosis factor-α and interleukin-6. In addition, RoMS decreased Toll-like receptor 4 protein expression in liver tissue. RoMS mitigated liver injury by activating DRs and negatively regulating the β-arrestin2-dependent Akt/NF-κB signaling pathway. The effects of RoMS could be weakened or abolished by the specific DRD2 antagonist, R121. In conclusion, activation of DRs inhibited the releases of pro-inflammatory cytokines and alleviated the immune-mediated liver injury induced by LPS in mice. The anti-inflammatory mechanism of RoMS may be related to the regulation of the β-arrestin2-dependent Akt/NF-κB signaling pathway.

Dopamine, a co-regulatory component, bridges the central nervous system and the immune system

Dopamine (DA) is a crucial neurotransmitter that plays an important role in maintaining physiological function in human body. In the past, most studies focused on the relationship between the dopaminergic system and neurological-related diseases. However, it has been found recently that DA is an immunomodulatory mediator and many immune cells express dopamine receptors (DRs). Some immune cells can synthesize and secrete DA and then participate in regulating immune function. DRs agonists or antagonists can improve the dysfunction of immune system through classical G protein signaling pathways or other non-receptor-dependent pathways. This article will discuss the relationship between the dopaminergic system and the immune system. It will also review the use of DRs agonists or antagonists to treat chronic and acute inflammatory diseases and corresponding immunomodulatory mechanisms.