N-octanoyl-dopamine is a potent inhibitor of platelet function

Investigating the role of rotenone on human blood platelets: Molecular insights into abnormal platelet functions in Parkinson's disease

Parkinson's disease (PD) is a predominant neuromotor disorder characterized by the selective death of dopaminergic neurons in the midbrain. The majority of PD cases are sporadic or idiopathic, with environmental toxins and pollutants potentially contributing to its development or exacerbation. However, clinical PD patients are often associated with a reduced stroke frequency, where circulating blood platelets are indispensable. Although platelet structural impairment is evident in PD, the platelet functional alterations and their underlying molecular mechanisms are still obscure. Therefore, we investigated rotenone (ROT), an environmental neurotoxin that selectively destroys dopaminergic neurons mimicking PD, on human blood platelets to explore its impact on platelet functions, thus replicating PD conditions in vitro. Our study deciphered that ROT decreased thrombin-induced platelet functions, including adhesion, activation, secretion, and aggregation in human blood platelets. As ROT is primarily responsible for generating intracellular reactive oxygen species (ROS), and ROS is a key player regulating the platelet functional parameters, we went on to check the effect of ROT on platelet ROS production. In our investigation, it became evident that ROT treatment resulted in the stimulation of ROS production in human blood platelets. Additionally, we discovered that ROT induced ROS production by augmenting Ca2+ mobilization from inositol 1,4,5-trisphosphate receptor. Apart from this, the treatment of ROT triggers protein kinase C associated NADPH oxidase-mediated ROS production in platelets. In summary, this research, for the first time, highlights ROT-induced abnormal platelet functions and may provide a mechanistic insight into the altered platelet activities observed in PD patients.

N-octanoyl dopamine is superior to dopamine in protecting graft contractile function when administered to the heart transplant recipients from brain-dead donors

The major source of heart transplantation comes from brain-dead (BD) donors. However, brain death and myocardial ischemia/reperfusion injury during transplantation may lead to cardiac dysfunction and hemodynamic instability. A previous work demonstrated that pre-treatment of BD donors with dopamine improved the graft survival of heart allograft in recipient after transplantation. However, low-dose dopamine treatment might result in tachycardia and hypertension. Our previous experimental study showed that pre-treatment of BD donor rats with the dopamine derivate N-octanoyl dopamine (NOD), devoid of any hemodynamic effects, improved graft function after transplantation. Herein, we hypothesized that NOD confers superior myocardial protection than dopamine, in terms of graft function. Male Lewis donor rats were either subjected to sham-operation or brain death via a subdurally placed balloon followed by 5.5 h monitoring. Then, the hearts were explanted and heterotopically transplanted into Lewis recipient rats. Shortly before the onset of reperfusion, continuous intravenous infusion of either NOD (14.7 μg/kg/min, BD + NOD group, n = 9), dopamine (10 μg/kg/min, BD + Dopamine group, n = 8) or physiological saline vehicle (sham, n = 9 and BD group, n = 9) were administered to the recipient rats. In vivo left-ventricular (LV) graft function was evaluated after 1.5 h reperfusion. Additionally, immunohistochemical detection of 4-hydroxy-2-nonenal (HNE, an indicator of oxidative stress) and nitrotyrosine (a nitro-oxidative stress marker), was performed. After heart transplantation, systolic and diastolic functions were significantly decreased in the BD group compared to sham. Treatment with NOD but not dopamine, resulted in better LV graft systolic functional recovery (LV systolic pressure BD + NOD 90 ± 8 vs BD + Dopamine 66 ± 5 vs BD 65 ± 4 mmHg; maximum rate of rise of LV pressure dP/dt_max BD + NOD 2686 ± 225 vs BD + Dopamine 2243 ± 70 vs BD 1999 ± 147 mmHg/s, at an intraventricular volume of 140 μl, p < 0.05) and myocardial work compared to BD group. The re-beating time (time to restoration of heartbeat) was significantly shorter in BD + NOD group than that of BD hearts (32 ± 4 s vs. 48 ± 6 s, p < 0.05), Dopamine treatment had no impact on all of these parameters. Furthermore, NOD as well as dopamine decreased HNE and nitrotyrosine immunoreactivity to the same level. NOD is superior to dopamine in terms of protecting LV graft contractile function when administered to the heart transplant recipients from BD donors.

Analyses of Synthetic N-Acyl Dopamine Derivatives Revealing Different Structural Requirements for Their Anti-inflammatory and Transient-Receptor-Potential-Channel-of-the-Vanilloid-Receptor-Subfamily-Subtype-1 (TRPV1)-Activating Properties

We studied the chemical entities within N-octanoyl dopamine (NOD) responsible for the activation of transient-receptor-potential channels of the vanilloid-receptor subtype 1 (TRPV1) and inhibition of inflammation. The potency of NOD in activating TRPV1 was significantly higher compared with those of variants in which the ortho-dihydroxy groups were acetylated, one of the hydroxy groups was omitted ( N-octanoyl tyramine), or the ester functionality consisted of a bulky fatty acid ( N-pivaloyl dopamine). Shortening of the amide linker (ΔNOD) slightly increased its potency, which was further increased when the carbonyl and amide groups (ΔNODR) were interchanged. With the exception of ΔNOD, the presence of an intact catechol structure was obligatory for the inhibition of VCAM-1 and the induction of HO-1 expression. Because TRPV1 activation and the inhibition of inflammation by N-acyl dopamines require different structural entities, our findings provide a framework for the rational design of TRPV1 agonists with improved anti-inflammatory properties.

Donor Preconditioning After the Onset of Brain Death With Dopamine Derivate n-Octanoyl Dopamine Improves Early Posttransplant Graft Function in the Rat

Heart transplantation is the therapy of choice for end-stage heart failure. However, hemodynamic instability, which has been demonstrated in brain-dead donors (BDD), could also affect the posttransplant graft function. We tested the hypothesis that treatment of the BDD with the dopamine derivate n-octanoyl-dopamine (NOD) improves donor cardiac and graft function after transplantation. Donor rats were given a continuous intravenous infusion of either NOD (0.882 mg/kg/h, BDD+NOD, n = 6) or a physiological saline vehicle (BDD, n = 9) for 5 h after the induction of brain death by inflation of a subdural balloon catheter. Controls were sham-operated (n = 9). In BDD, decreased left-ventricular contractility (ejection fraction; maximum rate of rise of left-ventricular pressure; preload recruitable stroke work), relaxation (maximum rate of fall of left-ventricular pressure; Tau), and increased end-diastolic stiffness were significantly improved after the NOD treatment. Following the transplantation, the NOD-treatment of BDD improved impaired systolic function and ventricular relaxation. Additionally, after transplantation increased interleukin-6, tumor necrosis factor TNF-α, NF-kappaB-p65, and nuclear factor (NF)-kappaB-p105 gene expression, and increased caspase-3, TNF-α and NF-kappaB protein expression could be significantly downregulated by the NOD treatment compared to BDD. BDD postconditioning with NOD through downregulation of the pro-apoptotic factor caspase-3, pro-inflammatory cytokines, and NF-kappaB may protect the heart against the myocardial injuries associated with brain death and ischemia/reperfusion.

N-octanoyl Dopamine Attenuates the Development of Transplant Vasculopathy in Rat Aortic Allografts Via Smooth Muscle Cell Protective Mechanisms

BACKGROUND

Transplant vasculopathy (TV) is a major cause for late graft loss after cardiac transplantation. Endothelial damage and T cell infiltration play a pivotal role in the development of TV. Because N-octanoyl dopamine (NOD) inhibits vascular inflammation and suppresses T cell activation in vitro, we here tested the hypothesis that NOD treatment ameliorates TV.

METHODS

Aortic grafts were orthotopically transplanted in the Dark Agouti to Brown Norway strain combination. Recipient rats were treated with NOD or vehicle administered via osmotic minipumps. Histology and quantitative polymerase chain reaction (qPCR) were performed on nontransplanted aortas and grafts explanted 2 and 4 weeks after transplantation to assess the degree of TV, inflammation, apoptosis, and number of (proliferating) α smooth muscle actin (αSMA) neointimal cells. In vitro analyses of human aortic smooth muscle cells were performed to test the effect of NOD on proliferation (WST-1 assay), cell cycle (flow cytometry and qPCR), and cytokine-induced apoptosis (flow cytometry).

RESULTS

Allografts from vehicle-treated recipients developed neointimal lesions predominantly consisting of αSMA-expressing cells. NOD treatment significantly reduced neointima formation and neointimal αSMA cells. In situ, smooth muscle cell proliferation (Ki67) was not influenced by NOD. Macrophage (CD68), T (CD3), and Natural Killer (ANK61) cell infiltration as well as intragraft TNFα and IFNγ mRNA expression were similar in both groups. Medial apoptosis (cleaved caspase-3) was significantly reduced by NOD. In vitro, NOD inhibited proliferation of human aortic smooth muscle cells by causing a G1-arrest and protected from TNFα-induced apoptosis.

CONCLUSIONS

This study identified NOD as potential treatment modality to attenuate TV. Our data clearly support a vasculoprotective effect of NOD by reducing smooth muscle cell proliferation and inflammation-induced apoptosis.

N-octanoyl dopamine treatment of endothelial cells induces the unfolded protein response and results in hypometabolism and tolerance to hypothermia

Aim

N-acyl dopamines (NADD) are gaining attention in the field of inflammatory and neurological disorders. Due to their hydrophobicity, NADD may have access to the endoplasmic reticulum (ER). We therefore investigated if NADD induce the unfolded protein response (UPR) and if this in turn influences cell behaviour.

Methods

Genome wide gene expression profiling, confirmatory qPCR and reporter assays were employed on human umbilical vein endothelial cells (HUVEC) to validate induction of UPR target genes and UPR sensor activation by N-octanoyl dopamine (NOD). Intracellular ATP, apoptosis and induction of thermotolerance were used as functional parameters to assess adaptation of HUVEC.

Results

NOD, but not dopamine dose dependently induces the UPR. This was also found for other synthetic NADD. Induction of the UPR was dependent on the redox activity of NADD and was not caused by selective activation of a particular UPR sensor. UPR induction did not result in cell apoptosis, yet NOD strongly impaired cell proliferation by attenuation of cells in the S-G2/M phase. Long-term treatment of HUVEC with low NOD concentration showed decreased intracellular ATP concentration paralleled with activation of AMPK. These cells were significantly more resistant to cold inflicted injury.

Conclusions

We provide for the first time evidence that NADD induce the UPR in vitro. It remains to be assessed if UPR induction is causally associated with hypometabolism and thermotolerance. Further pharmacokinetic studies are warranted to address if the NADD concentrations used in vitro can be obtained in vivo and if this in turn shows therapeutic efficacy.

N-Octanoyl dopamine transiently inhibits T cell proliferation via G1 cell-cycle arrest and inhibition of redox-dependent transcription factors

Recently, we developed a nonhemodynamic dopamine derivative, NOD, which has profound anti-inflammatory effects in vitro. As NOD also protects rats from ischemic AKI, the present study tested whether NOD is able to modulate cellular immunity for potential use as a T cell-suppressive agent. To this end, T cells were stimulated by anti-CD3/CD28 or PMA/ionomycin in the presence or absence of different concentrations of NOD. T cell proliferation, activation markers, intracellular cytokine expression, and activation of transcription factors were assessed. Whereas T cell proliferation was inhibited significantly by NOD at Day 3, proliferation was restored at Day 7 or later depending on the NOD concentration used. Inhibition of proliferation was reflected by a diminished CD25 expression and switch from naive to memory T cells. Early TCR activation events were unaffected, yet NF-κB and AP-1 were strongly inhibited by NOD. The inhibitory effect of NOD seemed to be dependent on its redox activity, as NOT, a redox-inactive NOD derivate, did not influence proliferation. NOD displayed synergistic effects with CNIs on T cell proliferation. Our data demonstrate that NOD displays T cell-suppressive activity. In keeping with its anti-inflammatory action and its beneficial effect on ischemia-induced AKI, NOD may be an interesting drug candidate to prevent CNI-related side-effects.