Receptor Family Agonists Research Articles

Peritumoral administration of DRibbles-pulsed antigen-presenting cells enhances the antitumor efficacy of anti-GITR and anti-PD-1 antibodies via an antigen presenting independent mechanism

BackgroundTNF receptor family agonists and checkpoint blockade combination therapies lead to minimal tumor clearance of poorly immunogenic tumors. Therefore, a need to enhance the efficacy of this combination therapy arises. Antigen-presenting cells (APCs) present antigen to T cells and steer the immune response through chemokine and cytokine secretion. DRibbles (DR) are tumor-derived autophagosomes containing tumor antigens and innate inflammatory adjuvants.MethodsUsing preclinical murine lung and pancreatic cancer models, we assessed the triple combination therapy of GITR agonist and PD-1 blocking antibodies with peritumoral injections of DRibbles-pulsed-bone marrow cells (BMCs), which consisted mainly of APCs, or CD103+ cross-presenting dendritic cells (DCs). Immune responses were assessed by flow cytometry. FTY720 was used to prevent T-cell egress from lymph nodes to assess lymph node involvement, and MHC-mismatched-BMCs were used to assess the necessity of antigen presentation by the peritumorally-injected DR-APCs.ResultsTritherapy increased survival and cures in tumor-bearing mice compared to combined antibody therapy or peritumoral DR-BMCs alone. Peritumorally-injected BMCs remained within the tumor for at least 14 days and tritherapy efficacy was dependent on both CD4+ and CD8+ T cells. Although the overall percent of tumor-infiltrating T cells remained similar, tritherapy increased the ratio of effector CD4+ T cells-to-regulatory T cells, CD4+ T-cell cytokine production and proliferation, and CD8+ T-cell cytolytic activity in the tumor. Despite tritherapy-induced T-cell activation and cytolytic activity in lymph nodes, this T-cell activation was not required for tumor regression and enhanced survival. Replacement of DR-BMCs with DR-pulsed-DCs in the tritherapy led to similar antitumor effects, whereas replacement with DRibbles was less effective but delayed tumor growth. Interestingly, peritumoral administration of DR-pulsed MHC-mismatched-APCs in the tritherapy led to similar antitumor effects as MHC-matched-APCs, indicating that the observed enhanced antitumor effect was mediated independently of antigen presentation by the administered APCs.ConclusionsOverall, these results demonstrate that peritumoral DR-pulsed-BMC/DC administration synergizes with GITR agonist and PD-1 blockade to locally modulate and sustain tumor effector T-cell responses independently of T cell priming and perhaps through innate inflammatory modulations mediated by the DRibbles adjuvant. We offer a unique approach to modify the tumor microenvironment to benefit T-cell-targeted immunotherapies.

A D2-like receptor family agonist produces analgesia in mechanonociception but not in thermonociception at the spinal cord level in rats

The administration of dopaminergic drugs produces analgesia in individuals experiencing different types of pain. Analgesia induced by these drugs at the spinal cord level is mediated by D2-like agonists, which specifically inhibit the detection of nociceptive stimuli by sensory afferents. The extent of the analgesia provided by spinal dopamine agonists remains controversial, and the cellular mechanism of this analgesic process is poorly understood. The objective of this study was to evaluate the analgesic effect of quinpirole, a D2-like agonist, based on two nociceptive tests and at various doses that were selected to specifically activate dopamine receptors. We found that intrathecal quinpirole administration produces analgesia of mechanical but not thermal nociception and that the analgesic effect of quinpirole is reversed by a mix of D2, D3, and D4 receptor-specific antagonists, suggesting that the activation of all D2-like receptors is involved in the analgesia produced by intrathecal quinpirole. The differential effect on thermal and mechanical nociception was also tested upon the activation of μ-opioid receptors. As reported previously, low doses of the μ-opioid receptor agonist DAMGO produced analgesia of only thermonociception. This evidence shows that a D2-like receptor agonist administered at the spinal cord level produces analgesia specific to mechanonociception but not thermonociception.

N -Benzyl-5-methoxytryptamines as Potent Serotonin 5-HT 2 Receptor Family Agonists and Comparison with a Series of Phenethylamine Analogues

N -Benzyl-5-methoxytryptamines as Potent Serotonin 5-HT 2 Receptor Family Agonists and Comparison with a Series of Phenethylamine Analogues

Working memory span capacity improved by a D2 but not D1 receptor family agonist

Patients with schizophrenia exhibit poor working memory (WM). Although several subcomponents of WM can be measured, evidence suggests the primary subcomponent affected in schizophrenia is span capacity (WMC). Indeed, the NIMH-funded MATRICS initiative recommended assaying the WMC when assessing the efficacy of a putative therapeutic for FDA approval. Although dopamine D1 receptor agonists improve delay-dependent memory in animals, evidence for improvements in WMC due to dopamine D1 receptor activation is limited. In contrast, the dopamine D2-family agonist bromocriptine improves WMC in humans. The radial arm maze (RAM) can be used to assess WMC, although complications due to ceiling effects or strategy confounds have limited its use. We describe a 12-arm RAM protocol designed to assess whether the dopamine D1-family agonist SKF 38393 (0, 1, 3, and 10 mg/kg) or bromocriptine (0, 1, 3, and 10 mg/kg) could improve WMC in C57BL/6N mice ( n = 12) in cross-over designs. WMC increased and strategy usage decreased with training. The dopamine D1 agonist SKF 38393 had no effect on WMC or long-term memory. Bromocriptine decreased WMC errors, without affecting long-term memory, consistent with human studies. These data confirm that WMC can be measured in mice and reveal drug effects that are consistent with reported effects in humans. Future research is warranted to identify the subtype of the D2-family of receptors responsible for the observed improvement in WMC. Finally, this RAM procedure may prove useful in developing animal models of deficient WMC to further assess putative treatments for the cognitive deficits in schizophrenia.

Dopamine's role in social modulation of infant isolation‐induced vocalization: II. Maternally modulated infant separation responses are regulated by D1‐ and D2‐family dopamine receptors

Mammalian infant behavior directed toward caregivers is critical to survival and may play a role in establishing social bonds. Most mammalian infants vocalize when isolated. Rat pups vocalize at a higher rate when isolated following an interaction with an adult female than after an interaction with littermates, a phenomenon termed maternal potentiation. We previously reported that the D2 receptor family agonist quinpirole disrupts maternal potentiation at a dose that does not alter vocalization rate following contact with littermates. Here we further examine the role of dopamine in maternal potentiation by testing effects of both D1 and D2 receptor family ligands, alone and in combination, on maternal potentiation. We tested the drugs' effects on isolation vocalization subsequent to littermate contact and then another isolation preceded by a brief "reunion" period of exposure either to the anesthetized dam or a handling-only "pickup" condition. D2 receptor stimulation blocked the increase in vocalizations following reunion with the dam. The D2 agonist effect in the dam-reunion condition was much larger than its small effect in the pickup condition, providing further evidence that D2 receptors exert a selective modulation of maternal potentiation. On the other hand, systemic administration of the D1 agonist SKF81297 reduced isolation vocalizations nonspecifically, across all the experimental conditions. Finally, the D1 and D2 receptor dual antagonist, alpha-flupenthixol, increased isolation vocalizations and disrupted potentiation, but at doses that also inhibited locomotion. We conclude that D2 receptor family activation has a more selective effect of disrupting maternal potentiation than D1 receptor family activation.

Ability of Monocyte-Derived Dendritic Cells To Secrete Oxygen Radicals in Response to Formyl Peptide Receptor Family Agonists Compared to That of Myeloid and Plasmacytoid Dendritic Cells

We show that human monocyte-derived dendritic cells (DC) differ considerably from freshly isolated blood-derived myeloid and plasmacytoid DC in their abilities to produce reactive oxygen species in response to different agonists to the formyl peptide receptor family and are thus poor representatives of blood DC in this field of research.

Dopamine D2 receptor activation increases vesicular dopamine uptake and redistributes vesicular monoamine transporter-2 protein

Recent studies demonstrate that multiple dopamine receptor subtypes contribute to the regulation of vesicular monoamine transporter-2 (VMAT-2) activity. The present studies extend these findings by demonstrating that administration of the nonselective dopamine D2 receptor family agonist, quinpirole, rapidly increased vesicular dopamine uptake in purified rat striatal vesicles. This effect occurred in both postnatal day 40 and 90 rats, and was associated with redistribution of the vesicular monoamine transporter-2 (VMAT-2) within nerve terminals. Neither a full nor a partial dopamine D1 receptor family agonist (SKF81297 nor SKF38393, respectively) affected vesicular dopamine uptake per se, nor the effect of quinpirole. Neither the dopamine D3 nor the D4 receptor antagonists, NGB2904 and clozapine, respectively, altered the quinpirole-mediated increase in uptake. However, the nonselective dopamine D2 receptor family antagonist, eticlopride, prevented the quinpirole-induced increase. Taken together, these data demonstrate that dopamine D2 receptor subtype activation increases vesicular dopamine uptake. Implications of this phenomenon with regard to the treatment of Parkinson's disease will be discussed.

Effects of intra-striatal GDNF on motor coordination and striatal electrophysiology in aged F344 rats ☆

The purpose of this study was to examine whether improvement in motor function could be demonstrated in old rats, and to see if GDNF affected post-synaptic DA function. Aged (20 month old) versus young rats were tested following GDNF treatment for postural control by using an inclined balance beam and a wire grip strength test. Rats were also examined electrophysiologically for spontaneous striatal cell firing rate alone and in the presence of DA receptor agonists, and histologically for the intensity of striatal TH staining, and number of DA containing nigral cells. Behavior was significantly improved in the aged animals who received central GDNF infusions, although the extent of improvement was less than what has been observed in 16-month-old rats. There was no effect of GDNF treatment in the aged animals on spontaneous firing rate in the striatum, or on the post synaptic response to locally applied D 1 and D 2 receptor family agonists. However, there was an effect of age alone on firing rate, and on the response to locally applied SKF 38393 and quinpirole. By using unbiased cell counting we observed no age-related decline in the number of TH positive cells in the substantia nigra. There was no effect of GDNF on the number of TH positive cells in the substantia nigra in either young or aged rats, although there were morphological improvements in DA neurons of the GDNF treated aged rats. These results replicate earlier studies showing an effect of age on striatal firing rate and dopamine receptor function, and suggest that the GDNF mediated improvement in behavior may be located other than post synaptically within the striatum.

Interactions between D1 and D2 dopamine receptor family agonists and antagonists: the effects of chronic exposure on behavior and receptor binding in rats and their clinical implications.

Functional interactions between dopamine receptor subtypes may affect behavioral and biochemical responses which serve as models for neuropsychiatric illnesses and the clinical effects of drug therapy. We evaluated the effects of chronic exposure to the selective D1 receptor antagonist SCH 23390, and the selective D2 receptor antagonist metoclopramide, on spontaneous and drug-induced behavior and receptor density in rats, and then determined how these effects would be modified by concurrent administration of antagonists or agonists [SKF 38393, LY 171555 (quinpirole)] selective for the complementary receptor subtype. Administered alone, both the D1 and D2 antagonists had acute cataleptic effects to which animals became tolerant following chronic treatment, but the selective antagonists had opposing effects on spontaneous locomotor activity. Both antagonists produced equivalent, supersensitive behavioral responses to apomorphine, and resulted in an increase in D2 receptor density. Coadministration of the D1 and D2 antagonists had a synergistic effect on catalepsy, attenuated the effects on spontaneous locomotor activity observed with either drug alone, and had an additive effect on both apomorphine-induced stereotypic behavior and D2 receptor proliferation. On the other hand, when either selective antagonist was combined with the agonist selective for the complementary receptor subtype, both D2 receptor proliferation and behavioral supersensitivity were completely blocked. Combined antagonist-agonist treatments had opposing effects on the development of tolerance to antagonist-induced catalepsy. D2 - but not D1 - receptor densities were correlated with animals' behavioral responses to apomorphine. There results support and extend the notion that complex functional interactions between D1 and D2 receptor families occur within the central nervous system, and suggest that novel effects might be derived from combined administration of receptor selective agonists and antagonists.

Analysis of the effects of intra-accumbens SKF-38393 and LY-171555 upon the behavioural satiety sequence

The outcome of intra-accumbens infusions of the dopamine D1 receptor family agonist SKF-38393 and the D2 receptor family agonist LY-171555 upon measures taken during the behavioural satiety sequence was assessed (0.01 micrograms, 0.1 micrograms, 1.0 micrograms in each case). Each drug was infused either separately, or together as a co-infusion in order to examine the functional relationship between these dopamine receptor subtypes within the nucleus accumbens. Measures of feeding did not change following infusions of SKF-38393 or LY-171555, whether infused separately or together. However, following separate infusion of the lowest dose tested of each drug (0.01 micrograms), the onset of resting was advanced. Moderate to high doses of SKF-38393 and LY-171555 (0.1 micrograms, 1.0 micrograms) infused separately resulted in a marked increase in activity at the expense of resting. Co-infusion of 0.01 micrograms of each drug also resulted in a dramatic increase in activity. Thus, measures of feeding behaviour were unchanged following excitation of D1 and D2 dopamine receptor families within the nucleus accumbens. In marked contrast, locomotor behaviour appeared to be under the potent synergistic control of these receptor families.

Dopamine D 1 receptor family agonists, SK&F38393, SK&F77434, and SK&F82958, Differentially affect locomotor activities in rats

Dopamine D 1 receptor family agonists, 2,3,4,5,-tetrahydro-7,8-dihydroxyl-1-phenyl- H-3-benzazepine (SK&F38393), 3-allyl-2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1 H-3-benzazepine (SK&F77434), and 3-allyl-6-chloro-2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1 H-3-benzazepine (SK&F82958), were compared for their behavioral effects on horizontal movement time, rearing time, stereotypy time, and thigmotaxis time. All agonists resulted in biphasic effects with attenuation followed by potentiation (0.01–10.0 mg/kg, SC). While SK&F38393 did not potentiate horizontal movement and rearing times, and had minor effects on thigmotaxis, SK&F77434 and SK&F82958 potentiated horizontal movement and rearing behaviors and attenuated thimotaxis. The results were discussed in terms of the binding characteristics and current receptor theory.

5-HT response of rat hippocampal pyramidal cell bodies

Serotonin (5-HT) responses of pyramidal neurones freshly dissociated from rat ventral hippocampal CA1 region were investigated by using nystatin-perforated whole-cell recording. These dissociated neurones lack most of the dendrites and axons. Application of nanomolar concentrations of 5-HT induced outward current with an increase of membrane conductance at a holding potential (VH) of -40 mV. The current was mimicked by alpha-methyl-5-HT (5-HT2 receptor family agonist), but not by 8-OH-DPAT (5-HT1 receptor family agonist). Ketanserin (5-HT2 receptor family antagonist) and spiperone (5-HT1A and 5-HT2 receptor family antagonist) blocked the current in a concentration dependent manner. These results suggests that 5-HT-induced outward current is mediated by the activation of 5-HT2 receptor family in the cell bodies of hippocampal pyramidal neurones.