Category: receptors

GHSR-D2R heteromerization modulates dopamine signaling through an effect on G protein conformation

Proc Natl Acad Sci U S A. 2018 Apr 24;115(17):4501-4506. doi: 10.1073/pnas.1712725115. Epub 2018 Apr 9

Damian M, Pons V, Renault P, M’Kadmi C, Delort B, Hartmann L, Kaya AI, Louet M, Gagne D, Ben Haj Salah K, Denoyelle S, Ferry G, Boutin JA, Wagner R, Fehrentz JA, Martinez J, Marie J, Floquet N, Galès C, Mary S, Hamm HE, Banères JL.

Abstract

IThe growth hormone secretagogue receptor (GHSR) and dopamine receptor (D2R) have been shown to oligomerize in hypothalamic neurons with a significant effect on dopamine signaling, but the molecular processes underlying this effect are still obscure. We used here the purified GHSR and D2R to establish that these two receptors assemble in a lipid environment as a tetrameric complex composed of two each of the receptors. This complex further recruits G proteins to give rise to an assembly with only two G protein trimers bound to a receptor tetramer. We further demonstrate that receptor heteromerization directly impacts on dopamine-mediated Gi protein activation by modulating the conformation of its α-subunit. Indeed, association to the purified GHSR:D2R heteromer triggers a different active conformation of Gαi that is linked to a higher rate of GTP binding and a faster dissociation from the heteromeric receptor. This is an additional mechanism to expand the repertoire of GPCR signaling modulation that could have implications for the control of dopamine signaling in normal and physiopathological conditions.

The GHR-R antagonist JMV 2959 neither induces malaise nor alters the malaise property of LiCl in the adult male rat

Physiol Behav. 2018 Jan 1;183:46-48. doi: 10.1016/j.physbeh.2017.10.017. Epub 2017 Oct 19.

Rodriguez JA, Fehrentz JA, Martinez J, Ben Haj Salah K, Wellman PJ.

Abstract

The orexigenic peptide ghrelin (GHR) interacts with ghrelin receptors (GHR-Rs) to modulate brain reinforcement and feeding circuits. Pharmacological inactivation of GHR-Rs via administration of the drug JMV 2959 attenuates the rewarding/reinforcing effects of several drugs of abuse including alcohol, morphine, amphetamine and nicotine. One view of these results is that inactivation of GHR-Rs taps into brain reinforcement/feeding circuits acted upon by drugs of abuse. An alternate explanation is that JMV 2959 may induce malaise, which in turn may limit reinforcement as well as food ingestion. This is a variable of interest given that nicotine alone can induce malaise which may be enhanced by JMV 2959. In the present study, we assessed the capacity of JMV 2959 to produce malaise using a conditioned taste aversion (CTA) task. Adult male rats were allowed to consume a 0.1% sodium saccharin solution and then injected IP with either vehicle, 0.4mg/kg nicotine, 3mg/kg JMV 2959, a combination of 0.4mg/kg nicotine and 3mg/kg JMV 2959, or 32mg/kg lithium chloride (a positive control known to support induction of CTA). Lithium chloride produced a robust avoidance of the saccharin solution in subsequent 2 bottle (water and saccharin) tests, whereas JMV 2959 alone did not induce CTA. The combination of JMV 2959 and nicotine induced a moderate degree of CTA that was similar to that produced by nicotine alone. These results suggest that JMV 2959 is unlikely to limit either reinforcement or food ingestion via induction of malaise.

Growth hormone secretagogues hexarelin and JMV2894 protect skeletal muscle from mitochondrial damages in a rat model of cisplatin-induced cachexia

Sci Rep. 2017 Oct 12;7(1):13017. doi: 10.1038/s41598-017-13504-y.

Sirago G, Conte E, Fracasso F, Cormio A, Fehrentz JA, Martinez J, Musicco C, Camerino GM, Fonzino A, Rizzi L, Torsello A, Lezza AMS, Liantonio A, Cantatore P, Pesce V.

Abstract

Chemotherapy can cause cachexia, which consists of weight loss associated with muscle atrophy. The exact mechanisms underlying this skeletal muscle toxicity are largely unknown and co-therapies to attenuate chemotherapy-induced side effects are lacking. By using a rat model of cisplatin-induced cachexia, we here characterized the mitochondrial homeostasis in tibialis anterior cachectic muscle and evaluated the potential beneficial effects of the growth hormone secretagogues (GHS) hexarelin and JMV2894 in this setting. We found that cisplatin treatment caused a decrease in mitochondrial biogenesis (PGC-1α, NRF-1, TFAM, mtDNA, ND1), mitochondrial mass (Porin and Citrate synthase activity) and fusion index (MFN2, Drp1), together with changes in the expression of autophagy-related genes (AKT/FoxO pathway, Atg1, Beclin1, LC3AII, p62) and enhanced ROS production (PRX III, MnSOD). Importantly, JMV2894 and hexarelin are capable to antagonize this chemotherapy-induced mitochondrial dysfunction. Thus, our findings reveal a key-role played by mitochondria in the mechanism responsible for GHS beneficial effects in skeletal muscle, strongly indicating that targeting mitochondrial dysfunction might be a promising area of research in developing therapeutic strategies to prevent or limit muscle wasting in cachexia.

Involvement of PPARγ in the Anticonvulsant Activity of EP-80317, a Ghrelin Receptor Antagonist

Front Pharmacol. 2017 Sep 22;8:676. doi: 10.3389/fphar.2017.00676. eCollection 2017.

Lucchi C, Costa AM, Giordano C, Curia G, Piat M, Leo G, Vinet J, Brunel L, Fehrentz JA, Martinez J, Torsello A, Biagini G.

Abstract

Ghrelin, des-acyl ghrelin and other related peptides possess anticonvulsant activities. Although ghrelin and cognate peptides were shown to physiologically regulate only the ghrelin receptor, some of them were pharmacologically proved to activate the peroxisome proliferator-activated receptor gamma (PPARγ) through stimulation of the scavenger receptor CD36 in macrophages. In our study, we challenged the hypothesis that PPARγ could be involved in the anticonvulsant effects of EP-80317, a ghrelin receptor antagonist. For this purpose, we used the PPARγ antagonist GW9662 to evaluate the modulation of EP-80317 anticonvulsant properties in two different models. Firstly, the anticonvulsant effects of EP-80317 were studied in rats treated with pilocarpine to induce status epilepticus (SE). Secondly, the anticonvulsant activity of EP-80317 was ascertained in the repeated 6-Hz corneal stimulation model in mice. Behavioral and video electrocorticographic (ECoG) analyses were performed in both models. We also characterized levels of immunoreactivity for PPARγ in the hippocampus of 6-Hz corneally stimulated mice. EP-80317 predictably antagonized seizures in both models. Pretreatment with GW9662 counteracted almost all EP-80317 effects both in mice and rats. Only the effects of EP-80317 on power spectra of ECoGs recorded during repeated 6-Hz corneal stimulation were practically unaffected by GW9662 administration. Moreover, GW9662 alone produced a decrease in the latency of tonic-clonic seizures and accelerated the onset of SE in rats. Finally, in the hippocampus of mice treated with EP-80317 we found increased levels of PPARγ immunoreactivity. Overall, these results support the hypothesis that PPARγ is able to modulate seizures and mediates the anticonvulsant effects of EP-80317.

Growth hormone secretagogues prevent dysregulation of skeletal muscle calcium homeostasis in a rat model of cisplatin-induced cachexia.

J Cachexia Sarcopenia Muscle. 2017, Jun;8(3):386-404. doi: 10.1002/jcsm.12185. Epub 2017 Mar 10.

Conte E, Camerino GM, Mele A, De Bellis M, Pierno S, Rana F, Fonzino A, Caloiero R, Rizzi L, Bresciani E, Ben Haj Salah K, Fehrentz JA, Martinez J, Giustino A, Mariggiò MA, Coluccia M, Tricarico D, Lograno MD, De Luca A, Torsello A, Conte D, Liantonio A.

Abstract

BACKGROUND:

Cachexia is a wasting condition associated with cancer types and, at the same time, is a serious and dose-limiting side effect of cancer chemotherapy. Skeletal muscle loss is one of the main characteristics of cachexia that significantly contributes to the functional muscle impairment. Calcium-dependent signaling pathways are believed to play an important role in skeletal muscle decline observed in cachexia, but whether intracellular calcium homeostasis is affected in this situation remains uncertain. Growth hormone secretagogues (GHS), a family of synthetic agonists of ghrelin receptor (GHS-R1a), are being developed as a therapeutic option for cancer cachexia syndrome; however, the exact mechanism by which GHS interfere with skeletal muscle is not fully understood.

METHODS:

By a multidisciplinary approach ranging from cytofluorometry and electrophysiology to gene expression and histology, we characterized the calcium homeostasis in fast-twitch extensor digitorum longus (EDL) muscle of adult rats with cisplatin-induced cachexia and established the potential beneficial effects of two GHS (hexarelin and JMV2894) at this level. Additionally, in vivo measures of grip strength and of ultrasonography recordings allowed us to evaluate the functional impact of GHS therapeutic intervention.

RESULTS:

Cisplatin-treated EDL muscle fibres were characterized by a ~18% significant reduction of the muscle weight and fibre diameter together with an up-regulation of atrogin1/Murf-1 genes and a down-regulation of Pgc1-a gene, all indexes of muscle atrophy, and by a two-fold increase in resting intracellular calcium, [Ca2+ ]i , compared with control rats. Moreover, the amplitude of the calcium transient induced by caffeine or depolarizing high potassium solution as well as the store-operated calcium entry were ~50% significantly reduced in cisplatin-treated rats. Calcium homeostasis dysregulation parallels with changes of functional ex vivo (excitability and resting macroscopic conductance) and in vivo (forelimb force and muscle volume) outcomes in cachectic animals. Administration of hexarelin or JMV2894 markedly reduced the cisplatin-induced alteration of calcium homeostasis by both common as well as drug-specific mechanisms of action. This effect correlated with muscle function preservation as well as amelioration of various atrophic indexes, thus supporting the functional impact of GHS activity on calcium homeostasis.

CONCLUSIONS:

Our findings provide a direct evidence that a dysregulation of calcium homeostasis plays a key role in cisplatin-induced model of cachexia gaining insight into the etiopathogenesis of this form of muscle wasting. Furthermore, our demonstration that GHS administration efficaciously prevents cisplatin-induced calcium homeostasis alteration contributes to elucidate the mechanism of action through which GHS could potentially ameliorate chemotherapy-associated cachexia.

JMV5656, A Novel Derivative of TLQP-21, Triggers the Activation of a Calcium-Dependent Potassium Outward Current in Microglial Cells

Front Cell Neurosci. 2017 Feb 23;11:41. doi: 10.3389/fncel.2017.00041. eCollection 2017

Rivolta I, Binda A, Molteni L, Rizzi L, Bresciani E, Possenti R, Fehrentz JA, Verdié P, Martinez J, Omeljaniuk RJ, Locatelli V, Torsello A.

Abstract

TLQP-21 (TLQPPASSRRRHFHHALPPAR) is a multifunctional peptide that is involved in the control of physiological functions, including feeding, reproduction, stress responsiveness, and general homeostasis. Despite the huge interest in TLQP-21 biological activity, very little is known about its intracellular mechanisms of action. In microglial cells, TLQP-21 stimulates increases of intracellular Ca2+ that may activate functions, including proliferation, migration, phagocytosis and production of inflammatory molecules. Our aim was to investigate whether JMV5656 (RRRHFHHALPPAR), a novel short analogue of TLQP-21, stimulates intracellular Ca2+ in the N9 microglia cells, and whether this Ca2+ elevation is coupled with the activation Ca2+-sensitive K+ channels. TLQP-21 and JMV5656 induced a sharp, dose-dependent increment in intracellular calcium. In 77% of cells, JMV5656 also caused an increase in the total outward currents, which was blunted by TEA (tetraethyl ammonium chloride), a non-selective blocker of voltage-dependent and Ca2+-activated potassium (K+) channels. Moreover, the effects of ion channel blockers charybdotoxin and iberiotoxin, suggested that multiple calcium-activated K+ channel types drove the outward current stimulated by JMV5656. Additionally, inhibition of JMV5656-stimulated outward currents by NS6180 (4-[[3-(trifluoromethyl)phenyl]methyl]-2H-1,4 benzothiazin-3(4H)-one) and TRAM-34 (triarylmethane-34), indicated that KCa3.1 channels are involved in this JMV5656 mechanisms of action. In summary, we demonstrate that, in N9 microglia cells, the interaction of JMV5656 with the TLQP-21 receptors induced an increase in intracellular Ca2+, and, following extracellular Ca2+ entry, the opening of KCa3.1 channels.

JMV2894, a novel growth hormone secretagogue, accelerates body mass recovery in an experimental model of cachexia

Endocrine, 2016, Pages: Ahead of Print

E. Bresciani, L. Rizzi, L. Molteni, M. Ravelli, A. Liantonio, K. Ben Haj Salah, J. A. Fehrentz, J. Martinez, R. J. Omeljaniuk, G. Biagini, V. Locatelli, A. Torsello

Abstract

Oncol. patients subjected to chemotherapy frequently present aphagia, malnutrition, and cachexia. The purpose of this study was to investigate whether selected growth hormone secretagogues including hexarelin, JMV2894 and JMV2951 could antagonize body wt. loss and wasting induced by cisplatin administration in rats. The three growth hormone secretagogues behaved as full agonists of the growth hormone secretagogues receptor both in terms of ability to stimulate calcium mobilization in Chinese hamster ovary cells and stimulation of growth hormone release in neonatal rats. Adult rats were (i) treated with vehicle throughout (controls), or (ii) treated with cisplatin (days 1-3) and a growth hormone secretagogues or vehicle, (days 1-12). Body wt. and food consumption were measured daily. Although all growth hormone secretagogues caused initial transient acute increases in food intake, the total amt. of food eaten by controls and growth hormone secretagogues treated groups over the 12 exptl. days was not significantly different. All groups pre-treated with cisplatin lost up to 5-10 % body wt. in the first 4 days; they subsequently gained wt. at a rate comparable with controls. Interestingly, rats which received JMV2894 demonstrated a faster gain in body wt. than any other growth hormone secretagogues treated group and at the end of the protocol reached a wt. similar to that of controls. JMV2894 did not stimulate perirenal and epididymal fat accumulation but reduced MuRF mRNA levels in skeletal muscles. In conclusion, our findings demonstrate that JMV2894 antagonizes cisplatin induced wt. loss in rats and may prove useful in antagonizing cachexia assocd. with cancer and chemotherapy in humans.

New ligands of the ghrelin receptor based on the 1,2,4-triazole scaffold by introduction of a second chiral center

Bioorganic & Medicinal Chemistry Letters, 2016, Volume: 26, Issue: 10, Pages: 2408-2412, DOI: 10.1016/j.bmcl.2016.04.003

M. Maingot, A. L Blayo, S. Denoyelle, C. M’Kadmi, M. Damian, S. Mary, D. Gagne, P. Sanchez, B. Aicher, P. Schmidt, G. Muller, M. Teifel, E. Gunther, J. Marie, J.-L. Baneres, J. Martinez, J. A. Fehrentz, 

Abstract

Introducing a second chiral center on the previously described 1,2,4-triazole, allowed us to increase diversity and elongate the ‘C-terminal part’ of the mol.  Therefore, the authors were able to explore mimics of the substance P analogs described as inverse agonists.  Some compds. presented affinities in the nanomolar range and potent biol. activities, while one exhibited a partial inverse agonist behavior similar to a Substance P analog.

Novel 1H-Pyrrolo[3,2-c]quinoline Based 5-HT6 Receptor Antagonists with Potential Application for the Treatment of Cognitive Disorders Associated with Alzheimer’s Disease

ACS Chemical Neuroscience, 2016, Volume: 7, Issue: 7, Pages: 972-983,  DOI: 10.1021/acschemneuro.6b00090

K. Grychowska, G. Satala, T. Kos, A. Partyka, E. Colacino, S. Chaumont-Dubel, X. Bantreil, A. Wesolowska, M. Pawlowski, J. Martinez, P. Marin, G. Subra, A. J. Bojarski, F. Lamaty, P. Popik, P. Zajdel 

Abstract

Modulators of the serotonin 5-HT6 receptor (5-HT6R) offer a promising strategy for the treatment of the cognitive deficits that are assocd. with dementia and Alzheimer’s disease.  Herein, we report the design, synthesis, and characterization of a novel class of 5-HT6R antagonists that is based on the 1H-pyrrolo[3,2-c]quinoline core.  The most active compds. exhibited comparable binding affinity to the ref. compd., SB-742457, and markedly improved selectivity.  Lead optimization led to the identification of (S)-1-[(3-chlorophenyl)sulfonyl]-4-(pyrrolidine-3-yl-amino)-1H-pyrrolo[3,2-c]quinoline (14) (Ki = 3 nM and Kb = 0.41 nM).  Pharmacol. characterization of the 5-HT6R’s constitutive activity at Gs signaling revealed that 14 behaved as a neutral antagonist, while SB-742457 was classified as an inverse agonist.  Both compds. 14 and SB-742457 reversed phencyclidine-induced memory deficits and displayed distinct procognitive properties in cognitively unimpaired animals (3 mg/kg) in NOR tasks.  Compds. 14 and SB-742457 were also active in the Vogel test, yet the anxiolytic effect of 14 was 2-fold higher (MED = 3 mg/kg).  Moreover, 14 produced, in a 3-fold higher dose (MED = 10 mg/kg), antidepressant-like effects that were similar to those produced by SB-742457 (MED = 3 mg/kg).  Together, these data suggest that the 4-(pyrrolidine-3-yl-amino)-1H-pyrrolo[3,2-c]quinoline scaffold is an attractive mol. framework for the development of procognitive agents.  The results are promising enough to warrant further detailed mechanistic studies on the therapeutic potential of 5-HT6R antagonists and inverse agonists for the treatment of cognitive decline and depression/anxiety symptoms that are comorbidities of Alzheimer’s disease.

In vivo stabilization of a gastrin-releasing peptide receptor antagonist enhances PET imaging and radionuclide therapy of prostate cancer in preclinical studies

Theranostics, 2016, Volume: 6, Issue: 1, Pages: 104-117, DOI: 10.7150/thno.13580

K. L. S. Chatalic, M. Konijnenberg, J. Nonnekens, H. de Blois, S. Erik, C. de Ridder, L. Brunel, J. A. Fehrentz, J. Martinez, D. C. van Gent, B. A. Nock, T. Maina, W. M. van Weerden, M. de Jong

Abstract

A single tool for early detection, accurate staging, and personalized treatment of prostate cancer (PCa) would be a major breakthrough in the field of PCa.  Gastrin-releasing peptide receptor (GRPR) targeting peptides are promising probes for a theranostic approach for PCa overexpressing GRPR.  However, the successful application of small peptides in a theranostic approach is often hampered by their fast in vivo degrdn. by proteolytic enzymes, such as neutral endopeptidase (NEP).  Here we show for the first time that co-injection of a NEP inhibitor (phosphoramidon (PA)) can lead to an impressive enhancement of diagnostic sensitivity and therapeutic efficacy of the theranostic 68Ga-/177Lu-JMV4168 GRPR-antagonist.  Co-injection of PA (300 μg) led to stabilization of 177Lu-JMV4168 in murine peripheral blood.  In PC-3 tumor-bearing mice, PA co-injection led to a two-fold increase in tumor uptake of 68Ga-/177Lu-JMV4168, 1 h after injection.  In positron emission tomog. (PET) imaging with 68Ga-JMV4168, PA co-injection substantially enhanced PC-3 tumor signal intensity.  Radionuclide therapy with 177Lu-JMV4168 resulted in significant regression of PC-3 tumor size.  Radionuclide therapy efficacy was confirmed by prodn. of DNA double strand breaks, decreased cell proliferation and increased apoptosis.  Increased survival rates were obsd. in mice treated with 177Lu-JMV4168 plus PA as compared to those without PA.  This data shows that co-injection of the enzyme inhibitor PA greatly enhances the theranostic potential of GRPR-radioantagonists for future application in PCa patients.