Dopamine inhibits the expression of proinflammatory cytokines of microglial cells through the formation of dopamine quinone in the mouse striatum

Repurposing celecoxib as adjuvant therapy in patients with Parkinsonian disease: a new therapeutic dawn: randomized controlled pilot study

BACKGROUND

The clinical presentations of Parkinson's disease (PD), a chronic neurodegenerative condition, include bradykinesia, hypokinesia, stiffness, resting tremor, and postural instability. Recently, neuroinflammation is involved in pathogenesis of PD. Application of nonsteroidal anti-inflammatory drugs captured attention to treat these neuroinflammation.

AIM

To investigate the possible effectiveness of celecoxib in patients with PD treated with conventional treatment.

METHODS

Sixty outpatients who fulfilled the inclusion requirements for PD were enrolled in this randomized, prospective, and controlled study. The patients were allocated into two groups at random (n = 30); the control group received standard PD treatment, consisting of levodopa/carbidopa, and the celecoxib group received standard PD treatment plus celecoxib. A neurologist evaluated each patient at the beginning of the treatment and after 6 months. Assessment of Unified Parkinson's disease rating scale (UPDRS) for each patient. Before and after treatment, α -synuclein (α-Syn), tumor necrosis factor alpha (TNF-α), Toll like receptors-4 (TLR-4), nuclear factor erythroid 2-related factor 2 (Nrf-2) and brain-derived neurotropic factor (BDNF) were assessed. Paired and unpaired t tests were used to assess statistical significance within and between groups respectively.

RESULTS

The celecoxib group exhibited a significant and statistical reduction in the level of measured parameters by unpaired t test as followed: TLR-4 (p = 0.004), TNF-α (p = 0.042), and α-Syn (p = 0.004) apart from a significant increase in BDNF (p = 0.0005) and Nrf-2 (p = 0.004), in comparison with the control group. Also, UPDRS was significantly decreased in celecoxib group (p < 0.05).

CONCLUSION

Celecoxib could be a promising adjuvant therapy in managing patients with PD.

TRIAL REGISTRATION NUMBER

NCT05962957.

Dopamine and its precursor levodopa inactivate SARS-CoV-2 main protease by forming a quinoprotein

Many studies show either the absence, or very low levels of, SARS-CoV-2 viral RNA and/or antigen in the brain of COVID-19 patients. Reports consistently indicate an abortive infection phenomenon in nervous cells despite the fact that they contain the SARS-CoV-2 receptor, ACE2. Dopamine levels in different brain regions are in the range of micromolar to millimolar concentrations. We have shown that sub-micromolar to low micromolar concentrations of dopamine or its precursor (levodopa) time- and dose-dependently inhibit the activity of SARS-CoV-2 main protease (Mpro), which is vital for the viral life cycle, by forming a quinoprotein. Thiol detection coupled with the assessment of Mpro activity suggests that among the 12 cysteinyl thiols, the active site, Cys145-SH, is preferentially conjugated to the quinone derived from the oxidation of dopamine or levodopa. LC-MS/MS analyses show that the Cys145-SH is covalently conjugated by dopamine- or levodopa-o-quinone. These findings help explain why SARS-CoV-2 causes inefficient replication in many nerve cell lines. It is well recognized that inhaled pulmonary drug delivery is the most robust therapy pathway for lung diseases. CVT-301 (orally inhaled levodopa) was approved by the FDA as a drug for Parkinson's patients prior to the outbreak of COVID-19 in 2018. Based on the fact that SARS-CoV-2 causes inefficient replication in the CNS with abundant endogenous Mpro inhibitor in addition to the current finding that levodopa has an Mpro-inhibitory effect somewhat stronger than dopamine, we should urgently investigate the use of CVT-301 as a lung-targeting, COVID-19, Mpro inhibitor.

Dopaminergic regulation of inflammation and immunity in Parkinson's disease: friend or foe?

Parkinson's disease (PD) is a neurodegenerative disease affecting 7-10 million people worldwide. Currently, there is no treatment available to prevent or delay PD progression, partially due to the limited understanding of the pathological events which lead to the death of dopaminergic neurons in the substantia nigra in the brain, which is known to be the cause of PD symptoms. The current available treatments aim at compensating dopamine (DA) deficiency in the brain using its precursor levodopa, dopaminergic agonists and some indirect dopaminergic agents. The immune system is emerging as a critical player in PD. Therefore, immune-based approaches have recently been proposed to be used as potential antiparkinsonian agents. It has been well-known that dopaminergic pathways play a significant role in regulating immune responses in the brain. Although dopaminergic agents are the primary antiparkinsonian treatments, their immune regulatory effect has yet to be fully understood. The present review summarises the current available evidence of the immune regulatory effects of DA and its mimics and discusses dopaminergic agents as antiparkinsonian drugs. Based on the current understanding of their involvement in the regulation of neuroinflammation in PD, we propose that targeting immune pathways involved in PD pathology could offer a better treatment outcome for PD patients.

Pramipexole inhibits formalin-induce acute and long-lasting mechanical hypersensitivity via NF-kB pathway in rats

Pain is one of the most frequent causes for patients to seek medical care. It interferes with daily functioning and affects the quality of life of the patient. There is a clear need to investigate nonopioid or non-nonsteroidal anti-inflammatory drug alternatives for the treatment of pain. In this study, we determined the effect of acute pre- and posttreatment with pramipexole (PPX), a dopamine D2/D3 selective agonist, on formalin 1%-induced acute and long-lasting nociceptive behavior sensitivity in rats. Moreover, we sought to investigate whether the antiallodynic and antihyperalgesic effect induced by PPX was mediated through the nuclear factor-κB (NF-kB) signaling pathway. Moreover, acute systemic pretreatment with PPX (1 and 3 mg/kg, ip) suppressed the formalin-induced nociceptive behavior during both phases of the formalin test and the development of formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. Acute systemic posttreatment with PPX (3 mg/kg, ip) reverted the formalin-induced long-lasting secondary mechanical allodynia and hyperalgesia. Furthermore, PPX inhibits the protein expression of NF-κB-p65 and the levels of tumor necrosis factor-α and interleukin-1β in the spinal cord of animals with secondary mechanical allodynia and hyperalgesia induced by formalin. These data suggest that PPX has a potential role in producing anti-inflammatory activity. Moreover, the antiallodynic and antihyperalgesic effects induced by PPX can be mediated through the NF-kB signaling pathway.

Peridontitis as a Risk Factor for Attention Deficit Hyperactivity Disorder: Possible Neuro-inflammatory Mechanisms

Periodontitis is a condition caused mostly by the creation of a biofilm by the bacterium P. gingivalis, which releases toxins and damages the tooth structure. Recent research studies have reported association between dental health and neuropsychiatric illnesses. Neuroinflammation triggered by the first systemic inflammation caused by the bacterium present in the oral cavities is a plausible explanation for such a relationship. Substantial amount of evidence supports the role of neuroinflammation and dysfunction of the dopaminergic system in the pathology of ADHD (Attention deficit hyperactivity disorders). Recent epidemiological, microbiological and inflammatory findings strengthen that, periodontal bacteria, which cause systemic inflammation can contribute to neuroinflammation and finally ADHD. Although both diseases are characterized by inflammation, the specific pathways and crosslink's between periodontitis and ADHD remain unknown. Here, the authors describe the inflammatory elements of periodontitis, how this dental illness causes systemic inflammation, and how this systemic inflammation contributes to deteriorating neuroinflammation in the evolution of ADHD. Therefore, the aim of this review is to present possible links and mechanisms that could confirm the evidence of this association.