Methamphetamine Activates Trace Amine Associated Receptor 1 to Regulate Astrocyte Excitatory Amino Acid Transporter-2 via Differential CREB Phosphorylation During HIV-Associated Neurocognitive Disorders

A trace amine associated receptor mediates antimicrobial immune response in the oyster Crassostrea gigas

Trace amine-associated receptors (TAARs) are a class of G protein-coupled receptors, playing an immunomodulatory function in the neuroinflammatory responses. In the present study, a TAAR homologue with a 7tm_classA_rhodopsin-like domain (designated as CgTAAR1L) was identified in oyster Crassostrea gigas. The abundant CgTAAR1L transcripts were detected in visceral ganglia and haemocytes compared to other tissues, which were 55.35-fold and 32.95-fold (p < 0.01) of those in adductor muscle, respectively. The mRNA expression level of CgTAAR1L in haemocytes significantly increased and reached the peak level at 3 h after LPS or Poly (I:C) stimulation, which was 4.55-fold and 12.35-fold of that in control group, respectively (p < 0.01). After the expression of CgTAAR1L was inhibited by the injection of its targeted siRNA, the mRNA expression levels of interleukin17s (CgIL17-1, CgIL17-5 and CgIL17-6), and defensin (Cgdefh1) significantly decreased at 3 h after LPS stimulation, which was 0.51-fold (p < 0.001), 0.39-fold (p < 0.01), 0.48-fold (p < 0.05) and 0.41-fold (p < 0.05) of that in the control group, respectively. The nuclear translocation of Cgp65 protein was suppressed in the CgTAAR1L-RNAi oysters. Furthermore, the number of Vibrio splendidus in the haemolymph of CgTAAR1L-RNAi oysters significantly increased (4.11-fold, p < 0.001) compared with that in the control group. In contrast, there was no significant difference in phagocytic rate of haemocytes to V. splendidus in the CgTAAR1L-RNAi oysters. These results indicated that CgTAAR1L played an important role in the immune defense against bacterial infection by inducing the expressions of interleukin and defensin.

Discovery of a Novel Chemo-Type for TAAR1 Agonism via Molecular Modeling

The search for novel effective TAAR1 ligands continues to draw great attention due to the wide range of pharmacological applications related to TAAR1 targeting. Herein, molecular docking studies of known TAAR1 ligands, characterized by an oxazoline core, have been performed in order to identify novel promising chemo-types for the discovery of more active TAAR1 agonists. In particular, the oxazoline-based compound S18616 has been taken as a reference compound for the computational study, leading to the development of quite flat and conformationally locked ligands. The choice of a "Y-shape" conformation was suggested for the design of TAAR1 ligands, interacting with the protein cavity delimited by ASP103 and aromatic residues such as PHE186, PHE195, PHE268, and PHE267. The obtained results allowed us to preliminary in silico screen an in-house series of pyrimidinone-benzimidazoles (1a-10a) as a novel scaffold to target TAAR1. Combined ligand-based (LBCM) and structure based (SBCM) computational methods suggested the biological evaluation of compounds 1a-10a, leading to the identification of derivatives 1a-3a (hTAAR1 EC50 = 526.3-657.4 nM) as promising novel TAAR1 agonists.

The genetic susceptibility analysis of TAAR1 rs8192620 to methamphetamine and heroin abuse and its role in impulsivity

Abnormal genetic polymorphism of trace amine-associated receptor 1 (TAAR1) rs8192620 site has been confirmed to induce methamphetamine (MA) use and drug craving. However, the genetic susceptibility difference between MA addicts and heroin addicts is unknown. This study evaluated genetic heterogeneity of TAAR1 rs8192620 between MA and heroin addicts and elucidated whether rs8192620 genotypes associated with discrepancy in emotional impulsivity, which would help to instruct individualized treatment in addiction via acting on TAAR1 and evaluate risk of varied drug addiction. Participants consisting of gender-matched 63 MA and 71 heroin abusers were enrolled in the study. Due to mixed drug usage in some MA addicts, MA users were further subdivided into 41 only-MA (only MA taking) and 22 mixed-drug (Magu composed of about 20% MA and 70% caffeine) abusers. Via inter-individual single nucleotide polymorphism (SNP) analysis and two-sample t tests, respectively, the genotypic and Barratt Impulsiveness Scale-11 (BIS-11) scores differences between groups were completed. With following genotypic stratification, the differences in BIS-11 scores between groups were analyzed through two-sample t test. Individual SNP analysis showed significant differences in alleles distribution of rs8192620 between MA and heroin subjects (p = 0.019), even after Bonferroni correction. The TT homozygotes of rs8192620 dominated in MA participants, while C-containing genotypes in heroin (p = 0.026). There was no association of genotypes of TAAR1 rs8192620 with addicts' impulsivity. Our research indicates that the TAAR1 gene polymorphism might mediate the susceptibility discrepancy between MA and heroin abuse.

TAAR1 Regulates Purinergic-induced TNF Secretion from Peripheral, But Not CNS-resident, Macrophages

Trace amine-associated receptor 1 (TAAR1) is an established neuroregulatory G protein-coupled receptor with recent studies suggesting additional functions related to immunomodulation. Our lab has previously investigated TAAR1 expression within cells of the innate immune system and herein we aim to further elucidate TAAR1 function in both peripherally-derived and CNS-resident macrophages. The selective TAAR1 agonist RO5256390 was used in combination with common damage associated molecular patterns (ATP and ADP) to observe the effect of TAAR1 agonism on modulating cytokine secretion and metabolic profiles. In mouse bone-marrow derived macrophages, TAAR1 agonism inhibited TNF secretion following ATP stimulation, which appeared to be downstream of an associated pro-inflammatory shift in metabolic profile and transcriptional regulation of TNF synthesis. In contrast, TAAR1 agonism had no effect on ADP-induced TNF and IL-6 secretion in mouse microglia in either the presence or absence of astrocytes. In summary, we report a novel interaction between TAAR1 and purinergic signaling in peripherally-derived, but not CNS-resident, macrophages. These findings provide the first evidence of trace aminergic and purinergic crosstalk, and support the potential for TAAR1 as a novel therapeutic target in inflammatory disorders.

A Non-Canonical Role for IRE1α Links ER and Mitochondria as Key Regulators of Astrocyte Dysfunction: Implications in Methamphetamine use and HIV-Associated Neurocognitive Disorders

Astrocytes are one of the most numerous glial cells in the central nervous system (CNS) and provide essential support to neurons to ensure CNS health and function. During a neuropathological challenge, such as during human immunodeficiency virus (HIV)-1 infection or (METH)amphetamine exposure, astrocytes shift their neuroprotective functions and can become neurotoxic. Identifying cellular and molecular mechanisms underlying astrocyte dysfunction are of heightened importance to optimize the coupling between astrocytes and neurons and ensure neuronal fitness against CNS pathology, including HIV-1-associated neurocognitive disorders (HAND) and METH use disorder. Mitochondria are essential organelles for regulating metabolic, antioxidant, and inflammatory profiles. Moreover, endoplasmic reticulum (ER)-associated signaling pathways, such as calcium and the unfolded protein response (UPR), are important messengers for cellular fate and function, including inflammation and mitochondrial homeostasis. Increasing evidence supports that the three arms of the UPR are involved in the direct contact and communication between ER and mitochondria through mitochondria-associated ER membranes (MAMs). The current study investigated the effects of HIV-1 infection and chronic METH exposure on astrocyte ER and mitochondrial homeostasis and then examined the three UPR messengers as potential regulators of astrocyte mitochondrial dysfunction. Using primary human astrocytes infected with pseudotyped HIV-1 or exposed to low doses of METH for 7 days, astrocytes had increased mitochondrial oxygen consumption rate (OCR), cytosolic calcium flux and protein expression of UPR mediators. Notably, inositol-requiring protein 1α (IRE1α) was most prominently upregulated following both HIV-1 infection and chronic METH exposure. Moreover, pharmacological inhibition of the three UPR arms highlighted IRE1α as a key regulator of astrocyte metabolic function. To further explore the regulatory role of astrocyte IRE1α, astrocytes were transfected with an IRE1α overexpression vector followed by activation with the proinflammatory cytokine interleukin 1β. Overall, our findings confirm IRE1α modulates astrocyte mitochondrial respiration, glycolytic function, morphological activation, inflammation, and glutamate uptake, highlighting a novel potential target for regulating astrocyte dysfunction. Finally, these findings suggest both canonical and non-canonical UPR mechanisms of astrocyte IRE1α. Thus, additional studies are needed to determine how to best balance astrocyte IRE1α functions to both promote astrocyte neuroprotective properties while preventing neurotoxic properties during CNS pathologies.

Covid-19 interface with drug misuse and substance use disorders

The coronavirus disease 2019 (Covid-19) pandemic intensified the already catastrophic drug overdose and substance use disorder (SUD) epidemic, signaling a syndemic as social isolation, economic and mental health distress, and disrupted treatment services disproportionally impacted this vulnerable population. Along with these social and societal factors, biological factors triggered by intense stress intertwined with incumbent overactivity of the immune system and the resulting inflammatory outcomes may impact the functional status of the central nervous system (CNS). We review the literature concerning SARS-CoV2 infiltration and infection in the CNS and the prospects of synergy between stress, inflammation, and kynurenine pathway function during illness and recovery from Covid-19. Taken together, inflammation and neuroimmune signaling, a consequence of Covid-19 infection, may dysregulate critical pathways and underlie maladaptive changes in the CNS, to exacerbate the development of neuropsychiatric symptoms and in the vulnerability to develop SUD. This article is part of the special Issue on 'Vulnerabilities to Substance Abuse'.

Synergistic Impairment of the Neurovascular Unit by HIV-1 Infection and Methamphetamine Use: Implications for HIV-1-Associated Neurocognitive Disorders

The neurovascular units (NVU) are the minimal functional units of the blood-brain barrier (BBB), composed of endothelial cells, pericytes, astrocytes, microglia, neurons, and the basement membrane. The BBB serves as an important interface for immune communication between the brain and peripheral circulation. Disruption of the NVU by the human immunodeficiency virus-1 (HIV-1) induces dysfunction of the BBB and triggers inflammatory responses, which can lead to the development of neurocognitive impairments collectively known as HIV-1-associated neurocognitive disorders (HAND). Methamphetamine (METH) use disorder is a frequent comorbidity among individuals infected with HIV-1. METH use may be associated not only with rapid HIV-1 disease progression but also with accelerated onset and increased severity of HAND. However, the molecular mechanisms of METH-induced neuronal injury and cognitive impairment in the context of HIV-1 infection are poorly understood. In this review, we summarize recent progress in the signaling pathways mediating synergistic impairment of the BBB and neuronal injury induced by METH and HIV-1, potentially accelerating the onset or severity of HAND in HIV-1-positive METH abusers. We also discuss potential therapies to limit neuroinflammation and NVU damage in HIV-1-infected METH abusers.

Trace amine-associated receptor 1 (TAAR1): Potential application in mood disorders: A systematic review

There is a need for innovation with respect to therapeutics in psychiatry. Available evidence indicates that the trace amine-associated receptor 1 (TAAR1) agonist SEP-363856 is promising, as it improves measures of cognitive and reward function in schizophrenia. Hedonic and cognitive impairments are transdiagnostic and constitute major burdens in mood disorders. Herein, we systematically review the behavioural and genetic literature documenting the role of TAAR1 in reward and cognitive function, and propose a mechanistic model of TAAR1's functions in the brain. Notably, TAAR1 activity confers antidepressant-like effects, enhances attention and response inhibition, and reduces compulsive reward seeking without impairing normal function. Further characterization of the responsible mechanisms suggests ion-homeostatic, metabolic, neurotrophic, and anti-inflammatory enhancements in the limbic system. Multiple lines of evidence establish the viability of TAAR1 as a biological target for the treatment of mood disorders. Furthermore, the evidence suggests a role for TAAR1 in reward and cognitive function, which is attributed to a cascade of events that are relevant to the cellular integrity and function of the central nervous system.