N-oleoyl-dopamine increases locomotor activity in the rat

Gut-inhabiting Clostridia build human GPCR ligands by conjugating neurotransmitters with diet- and human-derived fatty acids

Human physiology is regulated by endogenous signalling compounds, including fatty acid amides (FAAs), chemical mimics of which are made by bacteria. The molecules produced by human-associated microbes are difficult to identify because they may only be made in a local niche or they require a substrate sourced from the host, diet or other microbes. We identified a set of uncharacterized gene clusters in metagenomics data from the human gut microbiome. These clusters were discovered to make FAAs by fusing exogenous fatty acids with amines. Using an in vitro assay, we tested their ability to incorporate 25 fatty acids and 53 amines known to be present in the human gut, from which the production of six FAAs was deduced (oleoyl dopamine, oleoyl tyramine, lauroyl tryptamine, oleoyl aminovaleric acid, α-linolenoyl phenylethylamine and caproyl tryptamine). These molecules were screened against panels of human G-protein-coupled receptors to deduce their putative human targets. Lauroyl tryptamine is found to be an antagonist to the immunomodulatory receptor EBI2 against its native oxysterol ligand (0.98 μM half-maximal inhibitory concentration), is produced in culture by Eubacterium rectale and is present in human faecal samples. FAAs produced by Clostridia may serve as a mechanism to modulate their host by mimicking human signalling molecules.

A Single Injection of N-Oleoyldopamine, an Endogenous Agonist for Transient Receptor Potential Vanilloid-1, Induced Brain Hypothermia, but No Neuroprotective Effects in Experimentally Induced Cerebral Ischemia in Rats

Targeted temperature management, or therapeutic hypothermia, is a potent neuroprotective approach after ischemic brain injury. Hypothermia should be induced as soon as possible after the onset of acute stroke to assure better outcomes. Accordingly, drugs with a fast-acting hypothermic effect sustainable through the period of emergency transportation to hospital would have clinical advantages. Activation of the transient receptor potential vanilloid-1 (TRPV1) can induce hypothermia. Our immunohistochemical investigations confirmed that TRPV1 was distributed to perivascular and periventricular regions of the rat brain, where TRPV1 can be easily detected by TRPV1 agonists. An endogenous TRPV1 selective agonist, N-oleoyldopamine (OLDA), and a synthetic antagonist, AMG 9810, were injected intraperitoneally into healthy adult male Wister rats, and brain and core temperatures and gross motor activities were monitored. Comparison with baseline temperatures showed that TRPV1 injection immediately induced mild hypothermia (p < 0.05 in brain and p < 0.01 in body), and AMG 9810 induced immediate mild hyperthermia (not significant). However, the OLDA-induced hypothermia did not decrease lesion volume after middle carotid artery occlusion in rats. Relative to vehicle, OLDA yielded poorer outcomes and AMG 9810 yielded better outcomes in neurological scores and lesion size. Our study showed that, as an agonist of TRPV1, OLDA has suitable hypothermia-inducing properties, but did not decrease lesion volume. Therefore, the search for novel TRPV1 agonists and/or antagonists providing hypothermia and neuroprotection should continue. Further investigations should also target OLDA-induced transient hypothermia combined with long-term hypothermia maintenance with surface cooling, which mimics the anticipated clinical use of this class of drug.

Bioactive Oleic Derivatives of Dopamine: A Review of the Therapeutic Potential

Lipid derivatives of dopamine are a novel class of compounds raising a research interest due to the potential of their being a vehicle for dopamine delivery to the brain. The aim of the present paper is to review the main features of the two most prominent bioactive members of this family, namely, N-oleoyl-dopamine (OLDA) and 3'-O-methyl-N-oleoyl-dopamine (OMe-OLDA), with emphasis on the possible therapeutic properties.

Oleic Derivatives of Dopamine and Respiration

Ventilatory inhibition is considered an undesirable pharmacological side effect of pharmacotherapy in neurodegenerative conditions underlain by brain dopamine deficiency. In this context, oleic derivatives of dopamine or N-acyl-dopamines are novel substances that may be of high therapeutic interest as having the ability to cross the blood-brain barrier and acting in dopamine-like manner. In the present study we seek to define the influence of N-acyl-dopamines on lung ventilation and its hypoxic responses in the rat. We found that N-oleoyl-dopamine decreased both normoxic and peak hypoxic ventilation in response to 8% acute hypoxia, on average, by 31% and 41%, respectively. Its metabolite, 3'-O-methyl-N-oleoyl-dopamine, caused a 15% ventilatory decrease each, whereas an oleic ester derivative, 3'-O-oleoyl-N-oleoyl-dopamine, caused 11% and 19% ventilatory decreases, respectively. All three N-acyl-dopamines investigated displayed an inhibitory effect on ventilation. The findings indicate that 3'-O-methyl-N-oleoyl-dopamine and 3'-O-oleoyl-N-oleoyl-dopamine performed better than N-oleoyl-dopamine in term of less ventilatory suppression, albeit the differences among the three compounds were modest. We conclude that N-acyl-dopamines are worthy of intensified explorations as potential carriers of dopamine molecule in view of the lack of clinically effective methods of dopamine delivery into the brain in neurodegenerative conditions.

The role of Omega-3 and Omega-9 fatty acids for the treatment of neuropathic pain after neurotrauma

Omega-3 polyunsaturated fatty acids (PUFAs), such as docosaexaenoic acid (DHA) and eicosapentaenoic acid (EPA), mediate neuroactive effects in experimental models of traumatic peripheral nerve and spinal cord injury. Cellular mechanisms of PUFAs include reduced neuroinflammation and oxidative stress, enhanced neurotrophic support, and activation of cell survival pathways. Bioactive Omega-9 monounsaturated fatty acids, such as oleic acid (OA) and 2-hydroxy oleic acid (2-OHOA), also show therapeutic effects in neurotrauma models. These FAs reduces noxious hyperreflexia and pain-related anxiety behavior following peripheral nerve injury and improves sensorimotor function following spinal cord injury (SCI), including facilitation of descending inhibitory antinociception. The relative safe profile of neuroactive fatty acids (FAs) holds promise for the future clinical development of these molecules as analgesic agents. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

N-oleoyldopamine modulates activity of midbrain dopaminergic neurons through multiple mechanisms

N-oleoyl-dopamine (OLDA) is an amide of dopamine and oleic acid, synthesized in catecholaminergic neurons. The present study investigates OLDA targets in midbrain dopaminergic (DA) neurons. Substantia Nigra compacta (SNc) DA neurons recorded in brain slices were excited by OLDA in wild type mice. In transient receptor potential vanilloid 1 (TRPV1) knockout (KO) mice, however, SNc DA neurons displayed sustained inhibition of firing. In the presence of the dopamine type 2 receptor (D2R) antagonist sulpiride or the dopamine transporter blocker nomifensine no such inhibition was observed. Under sulpiride OLDA slightly excited SNc DA neurons, an action abolished upon combined application of the cannabinoid1 and 2 receptor antagonists AM251 and AM630. In ventral tegmental area (VTA) DA neurons from TRPV1 KO mice a transient inhibition of firing by OLDA was observed. Thus OLDA modulates the firing of nigrostriatal DA neurons through interactions with TRPV1, cannabinoid receptors and dopamine uptake. These findings suggest further development of OLDA-like tandem molecules for the treatment of movement disorders including Parkinson's disease.

Metabolism of N-acylated-dopamine

N-oleoyl-dopamine (OLDA) is a novel lipid derivative of dopamine. Its biological action includes the interaction with dopamine and the transient receptor potential vanilloid (TRPV1) receptors. It seems to be synthesized in a dopamine-like manner, but there has been no information on its degradation. The aim of the study was, therefore, to determine whether OLDA metabolism proceeds the way dopamine proper does. We addressed the issue by examining the occurrence of O-methylation of exogenously supplemented OLDA via catechol-O-methyltransferase (COMT) under in vitro, ex vivo, and in vivo conditions using rat brain tissue. The results show that OLDA was methylated by COMT in all conditions studied, yielding the O-methylated derivative. The methylation was reversed by tolcapone, a potent COMT inhibitor, in a dose-dependent manner. We conclude that OLDA enters the metabolic pathway of dopamine. Methylation of OLDA may enhance its bioactive properties, such as the ability to interact with TRPV1 receptors.

Peroxisomal and mitochondrial β-oxidation pathways influence the virulence of the pathogenic fungus Cryptococcus neoformans

An understanding of the connections between metabolism and elaboration of virulence factors during host colonization by the human-pathogenic fungus Cryptococcus neoformans is important for developing antifungal therapies. Lipids are abundant in host tissues, and fungal pathogens in the phylum basidiomycota possess both peroxisomal and mitochondrial β-oxidation pathways to utilize this potential carbon source. In addition, lipids are important signaling molecules in both fungi and mammals. In this report, we demonstrate that defects in the peroxisomal and mitochondrial β-oxidation pathways influence the growth of C. neoformans on fatty acids as well as the virulence of the fungus in a mouse inhalation model of cryptococcosis. Disease attenuation may be due to the cumulative influence of altered carbon source acquisition or processing, interference with secretion, changes in cell wall integrity, and an observed defect in capsule production for the peroxisomal mutant. Altered capsule elaboration in the context of a β-oxidation defect was unexpected but is particularly important because this trait is a major virulence factor for C. neoformans. Additionally, analysis of mutants in the peroxisomal pathway revealed a growth-promoting activity for C. neoformans, and subsequent work identified oleic acid and biotin as candidates for such factors. Overall, this study reveals that β-oxidation influences virulence in C. neoformans by multiple mechanisms that likely include contributions to carbon source acquisition and virulence factor elaboration.

N-oleoyl-dopamine decreases muscle rigidity induced by reserpine in rats

N-oleoyl-dopamine (OLDA), a product of condensation of oleic acid and dopamine (DA), is a bioactive compound that crosses the blood-brain barrier after systemic administration. The possibility arises that OLDA could have a potential role in treating DA-related disorders, such as Parkinsons disease (PD). In the present study we seek to determine whether OLDA would affect muscle tone and akinesia in two rat models of PD: the reserpine-evoked muscle rigidity and the reserpine- and haloperidol-induced catalepsy. We found that OLDA (20 mg/kg) significantly decreased muscle rigidity induced by reserpine (2.5 mg/kg), measured as an increased mechanical muscle resistance (MMG) in response to a passive extension and flexion of a rat hind limb at the ankle joint. Moreover, OLDA potently decreased the reserpine-enhanced tonic and reflex electromyographic (EMG) activities recorded before and during the movement, respectively. A lower dose of OLDA (10 mg/kg) failed to have appreciable effects. The reference compound L-DOPA (25 mg/kg) also attenuated the reserpine-increased MMG and EMG activities; the effects were, however, observed much later and were less prominent than those characteristic of OLDA. In contrast to the effects on muscle tone, OLDA (20 and 40 mg/kg) did not influence catalepsy induced by either reserpine (1.25 mg/kg) or haloperidol (0.5 mg/kg). In conclusion, the study demonstrates a novel biological action of N-oleoyl-dopamine consisting of lowering the reserpine-induced muscle rigidity. However, the lack of influence on akinesia suggests that the compound has myorelaxant rather than anti-Parkinsonian properties.