Duloxetine protected indomethacin-induced gastric mucosal injury by increasing serotonin-dependent RANTES expression and activating PI3K-AKT-VEGF pathway

Antidepressant duloxetine has been shown protective effect on indomethacin-induced gastric ulcer, which was escorted by inflammation in the gastric mucosa. Cytokines are the principal mediators of inflammation. Thus, by screening the differential expression of cytokines in the gastric mucosa using cytokine array at 3 h after indomethacin exposure, when the gastric ulcer began to format, we found that indomethacin increased cytokines which promoted inflammation responses, whereas duloxetine decreased pro-inflammatory cytokines increased by indomethacin and increased RANTES expression. RANTES was consistently increased by pretreated with both 5 mg/kg and 20 mg/kg duloxetine at 3 h and 6 h after indomethacin exposure in male rats. Selective blockade of RANTES-CCR5 axis by a functional antagonist Met-RANTES or a CCR5 antagonist maraviroc suppressed the protection of duloxetine. Considering the pharmacologic action of duloxetine on reuptake of monoamine neurotransmitters, we examined the serotonin (5-HT), norepinephrine and dopamine contents in the blood and discovered 20 mg/kg duloxetine increased 5-HT levels in platelet-poor plasma, while treatment with 5-HT promoted expression of RANTES in the gastric mucosa and alleviated the indomethacin-induced gastric injury. Furthermore, duloxetine activated PI3K-AKT-VEGF signaling pathway, which was regulated by RANTES-CCR5, and selective inhibitor of VEGF receptor axitinib blocked the prophylactic effect of duloxetine. Furthermore, duloxetine also protected gastric mucosa from indomethacin in female rats, and RANTES was increased by duloxetine after 6 h after indomethacin exposure too. Together, our results identified the role of cytokines, particularly RANTES, and the underlying mechanisms in gastroprotective effect of duloxetine against indomethacin, which advanced our understanding in inflammatory modulation by monoamine-based antidepressants.

Functional connectivity between the habenula and posterior default mode network contributes to the response of the duloxetine effect in major depressive disorder

This study aims to investigate the functional connectivity (FC) changes of the habenula (Hb) among patients with major depressive disorder (MDD) after 12 weeks of duloxetine treatment (MDD12). Patients who were diagnosed with MDD for the first time and were drug-naïve were recruited at baseline as cases. Healthy controls (HCs) matched for sex, age, and education level were also recruited at the same time. At baseline, all participants underwent resting-state functional MRI. FC analyses were performed using the Hb seed region of interest, and three groups including HCs, MDD group and MDD12 group were compared using whole-brain voxel-wise comparisons. Compared to the HCs, the MDD group had decreased FC between the Hb and the right anterior cingulate cortex at baseline. Compared to the HCs, the FC between the Hb and the left medial superior frontal gyrus decreased in the MDD12 group. Additionally, the FC between the left precuneus, bilateral cuneus and Hb increased in the MDD12 group than that in the MDD group. No significant correlation was found between HDRS-17 and the FC between the Hb, bilateral cuneus, and the left precuneus in the MDD12 group. Our study suggests that the FC between the post-default mode network and Hb may be the treatment mechanism of duloxetine and the treatment mechanisms and the pathogenesis of depression may be independent of each other.

Duloxetine HCl Alleviates Asthma Symptoms by Regulating PI3K/AKT/mTOR and Nrf2/HO-1 Signaling Pathways

Asthma is an inflammatory disease characterized by airway hyperresponsiveness, airway remodeling, and airway inflammation. In recent years, the prevalence of asthma has been increasing steadily and the pathogenesis of asthma varies from person to person. Due to poor compliance or resistance, existing drugs cannot achieve the desired therapeutic effect. Therefore, developing or screening asthma therapeutic drugs with high curative effects, low toxicity, and strong specificity is very urgent. Duloxetine HCl (DUX) is a selective serotonin and norepinephrine reuptake inhibitor, and it was mainly used to treat depression, osteoarthritis, and neuropathic pain. It was also reported that DUX has potential anti-infection, anti-inflammation, analgesic, antioxidative, and other pharmacological effects. However, whether DUX has some effects on asthma remains unknown. In order to investigate it, a series of ex vivo and in vivo experiments, including biological tension tests, patch clamp, histopathological analysis, lung function detection, oxidative stress enzyme activity detection, and molecular biology experiments, were designed in this study. We found that DUX can not only relax high potassium or ACh precontracted tracheal smooth muscle by regulating L-type voltage-dependent Ca2+ channel (L-VDCC) and nonselective cation channel (NSCC) ion channels but also alleviate asthma symptoms through anti-inflammatory and antioxidative response regulated by PI3K/AKT/mTOR and Nrf2/HO-1 signaling pathways. Our data suggests that DUX is expected to become a potential new drug for relieving or treating asthma.

Antidepressant duloxetine hydrochloride protects against ovariectomy-induced bone loss in mice by inhibiting osteoclast differentiation

BACKGROUND

Several studies have reported the association between osteoporosis and major depressive disorder (MDD) as well as the use of antidepressants. However, it remains to be elucidated whether these associations are related to exposure to antidepressants, a consequence of a disease process, or a combination of both.

METHODS

This study investigates the independent effect of the antidepressant duloxetine hydrochloride (DH) on ovariectomy-induced bone loss in mice. One week after ovariectomy, the treated mice received DH. To explore the mechanism underlying the rescue of bone loss, bone marrow cells were isolated from mouse femurs and tibias, and macrophages extracted from them were induced to become osteoclasts in vitro while being treated with DH. Subsequently, the osteoclasts underwent Bulk RNA-Seq to reveal the involved signaling pathways. The results of the bioinformatic analysis were then validated through in vitro experiments.

RESULTS

The in vivo experiments demonstrated that DH treatment compromised ovariectomy-induced bone loss after 7 weeks. The in vitro experiments suggested that DH treatment attenuated osteoclast differentiation via the MAPKs/NFATc1 signaling pathway.

CONCLUSION

The findings from this study suggest that DH, instead of causing bone mass loss, may assist in alleviating postmenopausal osteoporosis. These results can serve as a reference for the clinical treatment of patients with perimenopausal or postmenopausal depression using antidepressants.

Drugs possessing aryloxypropanamine pharmacophore, duloxetine, dapoxetine and propranolol, increase allopregnanolone in rat brain: Possible involvement of allopregnanolone in their central nervous system effects

Allopregnanolone (AP) is a neurosteroid synthesized in the brain and a positive allosteric modulator of γ-aminobutyric acid (GABA) type A receptors. Some drugs possessing the aryloxypropanamine (AOPA) pharmacophore, such as fluoxetine, exert their central nervous system (CNS) effects by increasing the brain AP. Although duloxetine (DLX), dapoxetine (DPX), atomoxetine (ATX) and propranolol (PRL) also possess the AOPA pharmacophore and are used to treat some psychiatric disorders, the capabilities of these drugs to increase the brain AP and the possible involvement of AP in their CNS effects remain to be fully elucidated. To clarify these points, we first developed a method for quantifying AP in the rat brain by liquid chromatography/electrospray ionization-tandem mass spectrometry. Analysis of the changes in the brain AP levels using this method revealed that the intraperitoneal administration of DLX (10 mg/kg), DPX (10 mg/kg) and PRL (20 mg/kg) significantly increased the brain AP (DLX: < 0.40-2.74 ng/g tissue, DPX: 1.48-3.83 ng/g tissue and PRL: < 0.40-2.09 ng/g tissue) compared to the saline administration (<0.40 ng/g tissue). These results suggested the possible involvement of the GABAergic neurosteroid, AP, in the central actions of DLX, DPX and PRL. In contrast, ATX (10 mg/kg) did not affect the AP levels in the brain. In addition, the brain and serum AP levels had a remarkably high positive correlation after the administration of DLX, DPX and PRL. Thus, this study proposed the AP-related novel mechanism of actions of DLX, DPX and PRL in the CNS.

The antidepressant drugs vortioxetine and duloxetine differentially and sex-dependently affect animal well-being, cognitive performance, cardiac redox status and histology in a model of osteoarthritis

Osteoarthritis represents a leading cause of disability with limited treatment options. Furthermore, it is frequently accompanied by cardiovascular and cognitive disorders, which can be exacerbated by osteoarthritis or drugs used for its treatment. Here, we examined the behavioral and cardiac effects of the novel antidepressant vortioxetine in an osteoarthritis model, and compared them to duloxetine (an established osteoarthritis treatment). Osteoarthritis was induced in male and female rats with an intraarticular sodium-monoiodoacetate injection. Antidepressants were orally administered for 28 days following induction. During this period the acetone, burrowing and novel-object-recognition tests (NORT) were used to assess the effects of antidepressants on pain hypersensitivity (cold allodynia), animal well-being and cognitive performance, respectively. Following behavioral experiments, heart muscles were collected for assessment of redox status/histology. Antidepressant treatment dose-dependently reduced cold allodynia in rats with osteoarthritis. Duloxetine (but not vortioxetine) depressed burrowing behavior in osteoarthritic rats in a dose-related manner. Osteoarthritis induction reduced cognitive performance in NORT, which was dose-dependently alleviated by vortioxetine (duloxetine improved performance only in female rats). Furthermore, duloxetine (but not vortioxetine) increased oxidative stress parameters in the heart muscles of female (but not male) rats and induced histological changes in cardiomyocytes indicative of oxidative damage. Vortioxetine displayed comparable efficacy to duloxetine in reducing pain hypersensitivity. Furthermore, vortioxetine (unlike duloxetine) dose-dependently improved cognitive performance and had no adverse effect on burrowing behavior (animal surrogate of well-being) and cardiac redox status/histology. Our results indicate that vortioxetine could be a potential osteoarthritis treatment (with better characteristics compared to duloxetine).

Upregulation by duloxetine of the transforming growth factor-α-induced migration of hepatocellular carcinoma cells via enhancement of the c-Jun N-terminal kinase activity

Duloxetine, a selective reuptake inhibitor for serotonin and norepinephrine, is a medication widely used for major depression. Currently, duloxetine is also recommended for pain related to chemotherapy-induced peripheral neuropathy or cancer. Previously, we showed that transforming growth factor-α (TGF-α) induces the migration of human hepatocellular carcinoma (HCC)-derived HuH7 cells through the activation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK) and AKT. In the present study, we investigate whether duloxetine affects cell migration and its mechanism. Duloxetine significantly enhanced the TGF-α-induced migration of HuH7 cells. Fluvoxamine and sertraline, specific inhibitors of serotonin reuptake, also upregulated the TGF-α-induced cell migration. On the contrary, reboxetine, a specific norepinephrine reuptake inhibitor, failed to affect cell migration. Duloxetine significantly amplified the TGF-α-stimulated phosphorylation of JNK, but not p38 MAPK and AKT. In addition, fluvoxamine and sertraline, but not reboxetine, enhanced the phosphorylation of JNK. SP600125, a JNK inhibitor, suppressed the enhancement by duloxetine, fluvoxamine, or sertraline of TGF-α-induced migration of HuH7 cells. Taken together, our results strongly suggest that duloxetine strengthens the TGF-α-induced activation of JNK via inhibition of serotonin reuptake in HCC cells, leading to the enhancement of cell migration.

Duloxetine and Amitriptyline Reduce Neuropathic Pain by Inhibiting Primary Sensory Input to Spinal Dorsal Horn Neurons via α1- and α2-Adrenergic Receptors

Antidepressants, such as duloxetine and amitriptyline, are effective for treating patients with chronic neuropathic pain. Inhibiting norepinephrine and serotonin transporters at presynaptic terminals raises extracellular concentrations of norepinephrine. The α1- and α2-adrenergic receptor agonists inhibit glutamatergic input from primary afferent nerves to the spinal dorsal horn. However, the contribution of spinal α1- and α2-adrenergic receptors to the analgesic effect of antidepressants and associated synaptic plasticity remains uncertain. In this study, we showed that systemic administration of duloxetine or amitriptyline acutely reduced tactile allodynia and mechanical and thermal hyperalgesia caused by spinal nerve ligation in rats. In contrast, duloxetine or amitriptyline had no effect on nociception in sham rats. Blocking α1-adrenergic receptors with WB-4101 or α2-adrenergic receptors with yohimbine at the spinal level diminished the analgesic effect of systemically administered duloxetine and amitriptyline. Furthermore, intrathecal injection of duloxetine or amitriptyline similarly attenuated pain hypersensitivity in nerve-injured rats; the analgesic effect was abolished by intrathecal pretreatment with both WB-4101 and yohimbine. In addition, whole-cell patch-clamp recordings in spinal cord slices showed that duloxetine or amitriptyline rapidly inhibited dorsal root-evoked excitatory postsynaptic currents in dorsal horn neurons in nerve-injured rats but had no such effect in sham rats. The inhibitory effect of duloxetine and amitriptyline was abolished by the WB-4101 and yohimbine combination. Therefore, antidepressants attenuate neuropathic pain predominantly by inhibiting primary afferent input to the spinal cord via activating both α1- and α2-adrenergic receptors. This information helps the design of new strategies to improve the treatment of neuropathic pain.

Identification of Spinal Inhibitory Interneurons Required for Attenuating Effect of Duloxetine on Neuropathic Allodynia-like Signs in Rats

Neuropathic pain is a chronic pain condition that occurs after nerve damage; allodynia, which refers to pain caused by generally innocuous stimuli, is a hallmark symptom. Although allodynia is often resistant to analgesics, the antidepressant duloxetine has been used as an effective therapeutic option. Duloxetine increases spinal noradrenaline (NA) levels by inhibiting its transporter at NAergic terminals in the spinal dorsal horn (SDH), which has been proposed to contribute to its pain-relieving effect. However, the mechanism through which duloxetine suppresses neuropathic allodynia remains unclear. Here, we identified an SDH inhibitory interneuron subset (captured by adeno-associated viral (AAV) vectors incorporating a rat neuropeptide Y promoter; AAV-NpyP⁺ neurons) that is mostly depolarized by NA. Furthermore, this excitatory effect was suppressed by pharmacological blockade or genetic knockdown of α_1B-adrenoceptors (ARs) in AAV-NpyP⁺ SDH neurons. We found that duloxetine suppressed Aβ fiber-mediated allodynia-like behavioral responses after nerve injury and that this effect was not observed in AAV-NpyP⁺ SDH neuron-selective α_1B-AR-knockdown. These results indicate that α_1B-AR and AAV-NpyP⁺ neurons are critical targets for spinal NA and are necessary for the therapeutic effect of duloxetine on neuropathic pain, which can support the development of novel analgesics.

Activity dependent inhibition of TRPC1/4/5 channels by duloxetine involves voltage sensor-like domain

Transient receptor potential canonical 5 (TRPC5) is a polymodal, calcium-permeable, nonselective ion channel that is expressed in the brain and 75 % of human sensory neurons. Its pharmacological or genetic inhibition leads to the relief of neuropathic and inflammatory pain. The clinically approved drug duloxetine is superior to other serotonin and norepinephrine reuptake inhibitors at managing painful neuropathies, but it is not known why. Here we ask whether the TRPC5 receptor is modulated by duloxetine and may contribute to its analgesic effect. Electrophysiological measurements of heterologously expressed human TRPC5 in HEK293T cells were performed to evaluate the effect of duloxetine. The interaction site was identified by molecular docking and molecular dynamics simulations in combination with point mutagenesis. We found that duloxetine inhibits TRPC5 in a concentration-dependent manner with a high potency (IC₅₀ = 0.54 ± 0.03 µM). Our data suggest that duloxetine binds into a voltage sensor-like domain. For the interaction, Glu⁴¹⁸ exhibited particular importance due to putative hydrogen bond formation. Duloxetine effectively inhibits TRPC5 currents induced by cooling, voltage, direct agonists and by the stimulation of the PLC pathway. The finding that this TRPC5 inhibitor is widely used and well tolerated provides a scaffold for new pain treatment strategies.

Duloxetine alleviates oxaliplatin-induced peripheral neuropathy by regulating p53-mediated apoptosis

Oxaliplatin (OXA) is a key platinum-based chemotherapeutic agent for treatment of metastatic colorectal cancer, but the side effects of acute and chronic neuropathies limit its clinical application. Duloxetine has been found to have the potential to prevent OXA-induced peripheral neuropathy in several studies, but the underlying mechanisms remain unclear. The purpose of this study was to evaluate the effects of duloxetine on OXA-induced peripheral neuropathy and to find the potential mechanisms. The neuropathic pain mice model was used to explore the role of duloxetine on OXA-induced peripheral neuropathy by measuring the change of thermal withdrawal latency (TWL), paw withdrawal threshold (PWT), and intraepidermal nerve fiber density (IENFD). Moreover, to explore molecular mechanisms, effects of duloxetine on OXA-induced changes in mRNA and protein expression of components of the p53-related pathways in cultured rat dorsal root ganglion (DRG) neurons were measured. In vivo, we found duloxetine treatment could significantly prevent the changes in the TWL, PWT to mechanical stimulation, and the IENFD of mice caused by OXA. In vitro, we found duloxetine notably inhibits the relative mRNA and protein expression levels of p53, Bax/Bcl2, caspase-3, and caspase-9 in DRG neurons, which may indicate duloxetine protected the DRG neuron by inhibiting p53-related pathways. These results suggest that duloxetine could alleviate the OXA-induced peripheral neuropathy. Duloxetine deserves further consideration as a potential protective agent against peripheral neuropathy.

The Potential Antidepressant Action of Duloxetine Co-Administered with the TAAR1 Receptor Agonist SEP-363856 in Mice

Here, we explored the possible interaction between duloxetine and SEP-363856 (SEP-856) in depression-related reactions. The results showed that oral administration of duloxetine showed powerful antidepressant-like effects in both the forced swimming test (FST) and the suspension tail test (TST). SEP-856 orally administered alone also exerted an antidepressant-like effect in FST and TST, especially at doses of 0.3, 1, and 10 mg/kg. In addition, duloxetine (15 mg/kg) and SEP-856 (15 mg/kg) both showed antidepressant-like effects in the sucrose preference test (SPT). Most importantly, in the above experiments, compared with duloxetine alone, the simultaneous use of duloxetine and SEP-856 caused a more significant antidepressant-like effect. It is worth noting that doses of drug combination in FST and TST did not change the motor activities of mice in the open-field test (OFT). Thus, duloxetine and SEP-856 seem to play a synergistic role in regulating depression-related behaviors and might be beneficial for refractory depression.

The Antidepressant Duloxetine Inhibits Platelet Function and Protects against Thrombosis

While cardiovascular disease (CVD) is the leading cause of death, major depressive disorder (MDD) is the primary cause of disability, affecting more than 300 million people worldwide. Interestingly, there is evidence that CVD is more prevalent in people with MDD. It is well established that neurotransmitters, namely serotonin and norepinephrine, are involved in the biochemical mechanisms of MDD, and consequently, drugs targeting serotonin-norepinephrine reuptake, such as duloxetine, are commonly prescribed for MDD. In this connection, serotonin and norepinephrine are also known to play critical roles in primary hemostasis. Based on these considerations, we investigated if duloxetine can be repurposed as an antiplatelet medication. Our results-using human and/or mouse platelets show that duloxetine dose-dependently inhibited agonist-induced platelet aggregation, compared to the vehicle control. Furthermore, it also blocked agonist-induced dense and α-granule secretion, integrin αIIbβ3 activation, phosphatidylserine expression, and clot retraction. Moreover duloxetine-treated mice had a significantly prolonged occlusion time. Finally, duloxetine was also found to impair hemostasis. Collectively, our data indicate that the antidepressant duloxetine, which is a serotonin-norepinephrine antagonist, exerts antiplatelet and thromboprotective effects and inhibits hemostasis. Consequently, duloxetine, or a rationally designed derivative, presents potential benefits in the context of CVD, including that associated with MDD.

Risk factors and pharmacotherapy for chemotherapy-induced peripheral neuropathy in paclitaxel-treated female cancer survivors: A retrospective study in Japan

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting adverse reaction in cancer patients treated with several cytotoxic anticancer agents including paclitaxel. Duloxetine, an antidepressant known as a serotonin-noradrenalin reuptake inhibitor, is the only agent that has moderate evidence for the use to treat painful CIPN. The present retrospective cohort study aimed to analyze risk factors for paclitaxel-induced peripheral neuropathy (PIPN), and investigate ongoing prescription drug use for PIPN in Japan. Female breast and gynecologic cancer patients who underwent paclitaxel-based chemotherapy at a single center in Japan between January 2016 and December 2019 were enrolled in this study. Patients’ information obtained from electronic medical records were statistically analyzed to test possible risk factors on PIPN diagnosis. Patients’ age, total paclitaxel dose, the history of female hormone-related diseases, hypertension and body mass index (BMI), but not additional platinum agents, were significantly associated with increased PIPN diagnosis. Drugs prescribed for PIPN included duloxetine, pregabalin, mecobalamin and Goshajinkigan, a polyherbal medicine, regardless of poor evidence for their effectiveness against CIPN, and were greatly different between breast and gynecologic cancer patients diagnosed with PIPN at the departments of Surgery and Gynecology, respectively. Thus, older age, greater total paclitaxel dose, the history of estrogen-related diseases, hypertension and BMI are considered risk factors for PIPN in paclitaxel-based chemotherapy of female cancer patients. It appears an urgent need to establish a guideline of evidence-based pharmacotherapy for PIPN.

Hippocampal BMP signaling as a common pathway for antidepressant action

The benefits of current treatments for depression are limited by low response rates, delayed therapeutic effects, and multiple side effects. Antidepressants affect a variety of neurotransmitter systems in different areas of the brain, and the mechanisms underlying their convergent effects on behavior have been unclear. Here we identify hippocampal bone morphogenetic protein (BMP) signaling as a common downstream pathway that mediates the behavioral effects of five different antidepressant classes (fluoxetine, bupropion, duloxetine, vilazodone, trazodone) and of electroconvulsive therapy. All of these therapies decrease BMP signaling and enhance neurogenesis in the hippocampus. Preventing the decrease in BMP signaling blocks the effect of antidepressant treatment on behavioral phenotypes. Further, inhibition of BMP signaling in hippocampal newborn neurons is sufficient to produce an antidepressant effect, while chemogenetic silencing of newborn neurons prevents the antidepressant effect. Thus, inhibition of hippocampal BMP signaling is both necessary and sufficient to mediate the effects of multiple classes of antidepressants.

Chronic Pain Produces Reversible Memory Deficits That Depend on Task Difficulty in Rats

Cognitive impairment associated with chronic pain remains relatively poorly understood. Use of analgesic drugs and often present co-morbidities in patients can preclude conclusions of causative relationships between chronic pain and cognitive deficits. Here, the impact of pain resulting from spinal nerve ligation (SNL) injury in rats on short and long-term memory was assessed in the novel object recognition task. To understand if chronic pain seizes the limited cognitive resources that are available at any given time, task difficulty was varied by using either very different (ie, easy task) or similar (ie, difficult task) pairs of objects. Nerve-injured, male rats exhibited no short or long-term memory deficits under easy task conditions. However, unlike sham-operated controls, injured rats showed deficits in both short and long-term memory by failing to differentiate similar objects in the difficult task version. In SNL rats, duloxetine produced anti-allodynic effects and ameliorated long-term memory deficits in the difficult task suggesting benefits of pain relief possibly complemented by noradrenergic mediated cognitive enhancement. Together these data suggest chronic pain reversibly takes up a significant amount of limited cognitive resources, leaving sufficient available for easy, but not difficult, tasks. PERSPECTIVE: Memory deficits in a rat model of chronic pain were only seen when the cognitive load was high, ie, in a difficult task. Acute treatment with duloxetine was sufficient to relieve memory deficits, suggesting chronic pain induces memory deficits by seizing limited cognitive resources to the detriment of task-related stimuli.

Cisplatin-induced neurotoxicity involves the disruption of serotonergic neurotransmission

Neurotoxicity is a frequent side effect of cisplatin (CisPt)-based anticancer therapy whose pathophysiology is largely vague. Here, we exploited C. elegans as a 3R-compliant in vivo model to elucidate molecular mechanisms contributing to CisPt-induced neuronal dysfunction. To this end, we monitored the impact of CisPt on various sensory functions as well as pharyngeal neurotransmission by recording electropharyngeograms (EPGs). CisPt neither affected food and odor sensation nor mechano-sensation, which involve dopaminergic and glutaminergic neurotransmission. However, CisPt reduced serotonin-regulated pharyngeal pumping activity independent of changes in the morphology of related neurons. CisPt-mediated alterations in EPGs were fully rescued by addition of serotonin (5-HT) (≤ 2 mM). Moreover, the CisPt-induced pharyngeal injury was prevented by co-incubation with the clinically approved serotonin re-uptake inhibitory drug duloxetine. A protective effect of 5-HT was also observed with respect to CisPt-mediated impairment of another 5-HT-dependent process, the egg laying activity. Importantly, CisPt-induced apoptosis in the gonad and learning disability were not influenced by 5-HT. Using different C. elegans mutants we found that CisPt-mediated (neuro)toxicity is independent of serotonin biosynthesis and re-uptake and likely involves serotonin-receptor subtype 7 (SER-7)-related functions. In conclusion, by measuring EPGs as a surrogate parameter of neuronal dysfunction, we provide first evidence that CisPt-induced neurotoxicity in C. elegans involves 5-HT-dependent neurotransmission and SER-7-mediated signaling mechanisms and can be prevented by the clinically approved antidepressant duloxetine. The data highlight the particular suitability of C. elegans as a 3R-conform in vivo model in molecular (neuro)toxicology and, moreover, for the pre-clinical identification of neuroprotective candidate drugs.

The Microglial Activation Inhibitor Minocycline, Used Alone and in Combination with Duloxetine, Attenuates Pain Caused by Oxaliplatin in Mice

The antitumor drug, oxaliplatin, induces neuropathic pain, which is resistant to available analgesics, and novel mechanism-based therapies are being evaluated for this debilitating condition. Since activated microglia, impaired serotonergic and noradrenergic neurotransmission and overexpressed sodium channels are implicated in oxaliplatin-induced pain, this in vivo study assessed the effect of minocycline, a microglial activation inhibitor used alone or in combination with ambroxol, a sodium channel blocker, or duloxetine, a serotonin and noradrenaline reuptake inhibitor, on oxaliplatin-induced tactile allodynia and cold hyperalgesia. To induce neuropathic pain, a single dose (10 mg/kg) of intraperitoneal oxaliplatin was used. The mechanical and cold pain thresholds were assessed using mouse von Frey and cold plate tests, respectively. On the day of oxaliplatin administration, only duloxetine (30 mg/kg) and minocycline (100 mg/kg) used alone attenuated both tactile allodynia and cold hyperalgesia 1 h and 6 h after administration. Minocycline (50 mg/kg), duloxetine (10 mg/kg) and combined minocycline + duloxetine influenced only tactile allodynia. Seven days after oxaliplatin, tactile allodynia (but not cold hyperalgesia) was attenuated by minocycline (100 mg/kg), duloxetine (30 mg/kg) and combined minocycline and duloxetine. These results indicate a potential usefulness of minocycline used alone or combination with duloxetine in the treatment of oxaliplatin-induced pain.

Identification and functional validation of FDA-approved positive and negative modulators of the mitochondrial calcium uniporter

The mitochondrial calcium uniporter (MCU), the highly selective channel responsible for mitochondrial Ca²⁺ entry, plays important roles in physiology and pathology. However, only few pharmacological compounds directly and selectively modulate its activity. Here, we perform high-throughput screening on a US Food and Drug Administration (FDA)-approved drug library comprising 1,600 compounds to identify molecules modulating mitochondrial Ca²⁺ uptake. We find amorolfine and benzethonium to be positive and negative MCU modulators, respectively. In agreement with the positive effect of MCU in muscle trophism, amorolfine increases muscle size, and MCU silencing is sufficient to blunt amorolfine-induced hypertrophy. Conversely, in the triple-negative breast cancer cell line MDA-MB-231, benzethonium delays cell growth and migration in an MCU-dependent manner and protects from ceramide-induced apoptosis, in line with the role of mitochondrial Ca²⁺ uptake in cancer progression. Overall, we identify amorolfine and benzethonium as effective MCU-targeting drugs applicable to a wide array of experimental and disease conditions.

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We screen an FDA-approved drug library for mitochondrial Ca²⁺ uptake modulators

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Amorolfine and benzethonium modulate MCU activity

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Amorolfine increases MCU-dependent mitochondrial metabolism and muscle size

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Benzethonium decreases MCU-dependent cancer cell growth and migration

Melancholic features (DSM-IV) predict but do not moderate response to antidepressants in major depression: an individual participant data meta-analysis of 1219 patients

It is sometimes clinically believed that major depression with melancholic features is more responsive to antidepressants than non-melancholic depression. Proper analysis and, therefore, valid evidence to support or refute this common clinical lore is lacking. The sample was taken from three placebo-controlled randomized trials of duloxetine, escitalopram and paroxetine (n = 1219). We conducted a two-step individual participant data meta-analysis to combine linear mixed-effects regressions modeling melancholic features as prognostic factor (variable that predicts overall response regardless of the treatments) and as effect modifier (variable that predict differential response to drug over placebo). Melancholic features represented a statistically significant prognostic factor for greater reduction in depression severity both on antidepressants and on placebo, especially after 4 weeks of treatment. However, they were not an effect modifier of the antidepressant treatment through the acute phase treatment: in other words. The superiority of antidepressants over placebo was not influenced by the melancholic features. The treatment decision-making as to the benefits of antidepressant treatment for patients with major depression should not be influenced by the presence or absence of melancholic features.

Small compounds mimicking the adhesion molecule L1 improve recovery in a zebrafish demyelination model

Demyelination leads to a loss of neurons, which results in, among other consequences, a severe reduction in locomotor function, and underlies several diseases in humans including multiple sclerosis and polyneuropathies. Considerable clinical progress has been made in counteracting demyelination. However, there remains a need for novel methods that reduce demyelination while concomitantly achieving remyelination, thus complementing the currently available tools to ameliorate demyelinating diseases. In this study, we used an established zebrafish demyelination model to test selected compounds, following a screening in cell culture experiments and in a mouse model of spinal cord injury that was aimed at identifying beneficial functions of the neural cell adhesion molecule L1. In comparison to mammalian nervous system disease models, the zebrafish allows testing of potentially promotive compounds more easily than what is possible in mammals. We found that our selected compounds tacrine and duloxetine significantly improved remyelination in the peripheral and central nervous system of transgenic zebrafish following pharmacologically induced demyelination. Given that both molecules are known to positively affect functions other than those related to L1 and in other disease contexts, we propose that their combined beneficial function raises hope for the use of these compounds in clinical settings.

Wide-Range Measurement of Thermal Preference-A Novel Method for Detecting Analgesics Reducing Thermally-Evoked Pain in Mice

Background: Wide use of oxaliplatin as an antitumor drug is limited by severe neuropathy with pharmacoresistant cold hypersensitivity as the main symptom. Novel analgesics to attenuate cold hyperalgesia and new methods to detect drug candidates are needed. Methods: We developed a method to study thermal preference of oxaliplatin-treated mice and assessed analgesic activity of intraperitoneal duloxetine and pregabalin used at 30 mg/kg. A prototype analgesiameter and a broad range of temperatures (0–45 °C) were used. Advanced methods of image analysis (deep learning and machine learning) enabled us to determine the effectiveness of analgesics. The loss or reversal of thermal preference of oxaliplatin-treated mice was a measure of analgesia. Results: Duloxetine selectively attenuated cold-induced pain at temperatures between 0 and 10 °C. Pregabalin-treated mice showed preference towards a colder plate of the two used at temperatures between 0 and 45 °C. Conclusion: Unlike duloxetine, pregabalin was not selective for temperatures below thermal preferendum. It influenced pain sensation at a much wider range of temperatures applied. Therefore, for the attenuation of cold hypersensitivity duloxetine seems to be a better than pregabalin therapeutic option. We propose wide-range measurements of thermal preference as a novel method for the assessment of analgesic activity in mice.

Topological network mechanisms of clinical response to antidepressant treatment in drug-naive major depressive disorder

AIM

There is rapidly increasing evidence that remission of MDD is associated with substantial changes in functional brain connectivity. These New data have provided a holistic view on the mechanism of antidepressants on multiple levels that goes beyond their conventional effects on neurotransmitters.

METHOD

The study was approved by the Local Ethics Committee of Istanbul Medipol University (10840098-604.01.01-E.65129) and followed the Helsinki Declaration principles. In our study, we have evaluated the effect of six weeks of treatment with antidepressants (escitalopram and duloxetine), and tested the underlying brain functional connectivity through a Graph analysis approach in a well-defined first-episode, drug-naive, and non-comorbid population with MDD.

RESULTS

Beyond indicating that there was a significant correlation between the antidepressant response and topological characteristics of the brain, our results suggested that global rather than regional network alterations may be implicated in the antidepressant effect.

CONCLUSION

Despite the small-sample size and non-controlled study design, our study provides important and relevant clinical data regarding the underlying mechanisms of the antidepressants on topological dynamics in the human brain.

Loss of diffuse noxious inhibitory control after traumatic brain injury in rats: A chronic issue

Chronic pain is one of the most challenging and debilitating symptoms to manage after traumatic brain injury (TBI), yet the underlying mechanisms remain elusive. The disruption of normal endogenous pain control mechanisms has been linked to several forms of chronic pain and may play a role in pain after TBI. We hypothesized therefore that dysfunctional descending noradrenergic and serotonergic pain control circuits may contribute to the loss of diffuse noxious inhibitory control (DNIC), a critical endogenous pain control mechanism, weeks to months after TBI. For these studies, the rat lateral fluid percussion model of mild TBI was used along with a DNIC paradigm involving a capsaicin-conditioning stimulus. We observed sustained failure of the DNIC response up to 180-days post injury. We confirmed, that descending α₂ adrenoceptor-mediated noradrenergic signaling was critical for endogenous pain inhibition in uninjured rats. However, augmenting descending noradrenergic signaling using reboxetine, a selective noradrenaline reuptake inhibitor, failed to restore DNIC after TBI. Furthermore, blocking serotonin-mediated descending signaling using selective spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine was also unsuccessful at restoring endogenous pain modulation after TBI. Unexpectedly, increasing descending serotonergic signaling using the selective serotonin reuptake inhibitor escitalopram and the serotonin-norepinephrine reuptake inhibitor duloxetine restored the DNIC response in TBI rats at both 49- and 180- days post injury. Consistent with these observations, spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine eliminated the effects of escitalopram. Intact α₂ adrenoceptor signaling, however, was not required for the serotonin-mediated restoration of DNIC after TBI. These results suggest that TBI causes maladaptation of descending nociceptive signaling mechanisms and changes in the function of both adrenergic and serotonergic circuits. Such changes could predispose those with TBI to chronic pain.

Duloxetine ameliorates the impairment of diffuse noxious inhibitory control in rat models of peripheral neuropathic pain and knee osteoarthritis pain

Diffuse noxious inhibitory control (DNIC) is a phenomenon to reflect descending pain modulation in animals. Conditioned pain modulation (CPM) is the human counterpart of DNIC and is reduced in patients with several chronic pain conditions. Duloxetine is a serotonin and noradrenaline reuptake inhibitor that ameliorates CPM impairment in patients with diabetic neuropathy. Although some studies have reported the effects of different pharmacological agents on CPM, few studies have compared the effects of some analgesics in both humans and rodents. Therefore, we established a stable evaluation method for DNIC in rats and determined whether duloxetine and other specific analgesics affect DNIC impairment in rat models of peripheral neuropathic pain and osteoarthritis pain, two types of chronic pain. As a conditioning stimulus, capsaicin was injected into the forepaw of rats. The paw withdrawal threshold (PWT) in response to mechanical pressure was measured for the hindpaw. Peripheral neuropathic pain and osteoarthritis pain models were developed by partial sciatic nerve ligation (PSNL) and the intra-articular injection of 2 mg monoiodoacetate (MIA), respectively. Capsaicin (30-100 μg/site) increased the PWT, in a dose-dependent manner, in naive rats. The threshold significantly increased at 30 μg and reached its maximal level at 100 μg. The change in PWT following capsaicin injection was significantly reduced in PSNL-treated rats, but the threshold was increased by the subcutaneous administration of duloxetine (10 mg/kg). The oral administrations of pregabalin (10 mg/kg) and celecoxib (3 mg/kg) did not affect the PWT in PSNL-treated rats. Similarly, MIA-injected rats also showed a reduced change in PWT following capsaicin injection. Duloxetine, but not pregabalin and celecoxib, significantly increased the PWT in MIA-injected rats. These results suggested that duloxetine can directly ameliorate DNIC impairment in rat models of chronic pain. Duloxetine may be useful for modulating chronic pain by restoring function to the endogenous, descending, inhibitory pathway.

The association between antidepressant treatment and brain connectivity in two double-blind, placebo-controlled clinical trials: a treatment mechanism study

BACKGROUND

Antidepressant medications offer an effective treatment for depression, yet nearly 50% of patients either do not respond or have side-effects rendering them unable to continue the course of treatment. Mechanistic studies might help advance the pharmacology of depression by identifying pathways through which treatments exert their effects. Toward this goal, we aimed to identify the effects of antidepressant treatment on neural connectivity, the relationship with symptom improvement, and to test whether these effects were reproducible across two studies.

METHODS

We completed two double-blind, placebo-controlled trials of SNRI antidepressant medications with MRI scans obtained before and after treatment. One was a 10-week trial of duloxetine (30-120 mg daily; mean 92·1 mg/day [SD 30·00]) and the other was a 12-week trial of desvenlafaxine (50-100 mg daily; 93·6 mg/day [16·47]). Participants consisted of adults with persistent depressive disorder. Adjusting for sex and age, we examined the effect of treatment on whole-brain functional connectivity. We also examined correlations between change in functional connectivity and improvement in symptoms of depression (24-item Hamilton Depression Rating Scale) and pain symptom severity (Symptom Checklist-90-Revised).

FINDINGS

Participants were enrolled between Jan 26, 2006, and Nov 22, 2011, for the duloxetine RCT and Aug 5, 2012, and Jan 28, 2016, for the desvenlafaxine RCT. Before and after treatment MRI scans were collected in 32 participants for the duloxetine RCT and 34 participants for the desvenlafaxine RCT. In both studies, antidepressants decreased functional connectivity compared with placebo (duloxetine study: β=-0·06; 95% CI -0·08 to -0·03; p<0·0001, ηp2=0·44; desvenlafaxine study: -0·06, -0·09 to -0·03; p<0·0001, ηp2=0·35) within a thalamo-cortico-periaqueductal network that has previously been associated with the experience of pain. Within the active drug groups, reductions in functional connectivity within this network correlated with improvements in depressive symptom severity in both studies (duloxetine study: r=0·38, 95% CI 0·01-0·65; p=0·0426; desvenlafaxine study: 0·44, 0·10-0·69; p=0·0138) and pain symptoms in the desvenlafaxine study (0·39, 0·04 to 0·65; p=0·0299).

INTERPRETATION

The findings suggest the thalamo-cortico-periaqueductal network associated with the experience of pain is a new and potentially important target for novel antidepressant therapeutics.

FUNDING

National Mental Health Institute, Eli Lilly and Company, Pfizer Pharmaceuticals, and the Edwin S Webster Foundation.

Anticonvulsive activity of duloxetine: A new choice for the epileptic patients with depression

The aim of this study was to investigate the antiepileptic effects of duloxetine in the maximal electroshock test and convulsions induced by four compounds: Pentylenetetrazole, 3-mercaptopropionic acid, thiosemicarbazide, and bicuculline. Duloxetine exhibited moderate anticonvulsive activity with an ED₅₀ (median effective dose) of 48.21 mg/kg in the maximal electroshock test in mice. The anticonvulsive action of duloxetine was also confirmed in chemical-induced seizure tests, where this drug decreased tonic convulsions. Single administration of duloxetine (6.25-25 mg/kg) significantly increased the anticonvulsant effects of valproate, carbamazepine, and oxcarbazepine in the maximal electroshock test. Furthermore, pretreatment with thiosemicarbazide (an inhibitor of GABA synthesis enzyme) significantly increased the ED₅₀ of duloxetine, suggesting the GABAergic system may contribute to the anticonvulsive action of duloxetine. These results support the use of duloxetine in the treatment of coexisting depression and epilepsy.

[Pharmacological profile of a novel nonhuman primate model of knee osteoarthritis]

A number of promising compounds developed in rodent arthritis models lack efficacy in clinical osteoarthritis (OA) pain. To enhance successful translation of preclinical findings, a nonhuman primate (NHP) model of knee OA was developed and characterized using behavioral assessments designed for use in the NHP. A unilateral medial meniscectomy (MMx) was performed and animals underwent an exercise regimen. Decreased ipsilateral knee pressure threshold, pressure "hyperalgesia", and decreased ipsilateral weight bearing, suggestive of pain at rest were observed. The sensitivity of the pain-related behaviors to pharmacological manipulation was evaluated. A single dose of the opioid morphine reduced pain-related behaviors. Likewise, the serotonin-norepinephrine reuptake inhibitor duloxetine reduced pain-related behavior, and efficacy was similar to that of morphine. By contrast, the anticonvulsant pregabalin did not significantly affect pain-related behavior. Repeated dosing with the non-steroidal anti-inflammatory drug (NSAID) diclofenac reduced pain-related behaviors whereas repeated dosing with the NK₁ receptor antagonist aprepitant did not. The drug effects observed in the NHP OA model mirror the efficacy observed clinically.

Serotonin and Norepinephrine Reuptake Inhibitors

This chapter covers antidepressants that fall into the class of serotonin (5-HT) and norepinephrine (NE) reuptake inhibitors. That is, they bind to the 5-HT and NE transporters with varying levels of potency and binding affinity ratios. Unlike the selective serotonin (5-HT) reuptake inhibitors (SSRIs), most of these antidepressants have an ascending rather than a flat dose-response curve. The chapter provides a brief review of the chemistry, pharmacology, metabolism, safety and adverse effects, clinical use, and therapeutic indications of each antidepressant. Venlafaxine, a phenylethylamine, is a relatively weak 5-HT and weaker NE uptake inhibitor with a 30-fold difference in binding of the two transporters. Therefore, the drug has a clear dose progression, with low doses predominantly binding to the 5-HT transporter and more binding of the NE transporter as the dose ascends. Venlafaxine is metabolized to the active metabolite O-desmethylvenlafaxine (ODV; desvenlafaxine) by CYP2D6, and it therefore is subject to significant inter-individual variation in blood levels and response dependent on variations in CYP2D6 metabolism. The half-life of venlafaxine is short at about 5 h, with the ODV metabolite being 12 h. Both parent compound and metabolite have low protein binding and neither inhibit CYP enzymes. Therefore, both venlafaxine and desvenlafaxine are potential options if drug-drug interactions are a concern, although venlafaxine may be subject to drug-drug interactions with CYP2D6 inhibitors. At low doses, the adverse effect profile is similar to an SSRI with nausea, diarrhea, fatigue or somnolence, and sexual side effects, while venlafaxine at higher doses can produce mild increases in blood pressure, diaphoresis, tachycardia, tremors, and anxiety. A disadvantage of venlafaxine relative to the SSRIs is the potential for dose-dependent blood pressure elevation, most likely due to the NE reuptake inhibition caused by higher doses; however, this adverse effect is infrequently observed at doses below 225 mg per day. Venlafaxine also has a number of potential advantages over the SSRIs, including an ascending dose-antidepressant response curve, with possibly greater overall efficacy at higher doses. Venlafaxine is approved for MDD as well as generalized anxiety disorder, social anxiety disorder, and panic disorder. Desvenlafaxine is the primary metabolite of venlafaxine, and it is also a relatively low-potency 5-HT and NE uptake inhibitor. Like venlafaxine it has a favorable drug-drug interaction profile. It is subject to CYP3A4 metabolism, and it is therefore vulnerable to enzyme inhibition or induction. However, the primary metabolic pathway is direct conjugation. It is approved in the narrow dose range of 50-100 mg per day. Duloxetine is a more potent 5-HT and NE reuptake inhibitor with a more balanced profile of binding at about 10:1 for 5HT and NE transporter binding. It is also a moderate inhibitor of CYP2D6, so that modest dose reductions and careful monitoring will be needed when prescribing duloxetine in combination with drugs that are preferentially metabolized by CYP2D6. The most common side effects identified in clinical trials are nausea, dry mouth, dizziness, constipation, insomnia, asthenia, and hypertension, consistent with its mechanisms of action. Clinical trials to date have demonstrated rates of response and remission in patients with major depression that are comparable to other marketed antidepressants reviewed in this book. In addition to approval for MDD, duloxetine is approved for diabetic peripheral neuropathic pain, fibromyalgia, and musculoskeletal pain. Milnacipran is marketed as an antidepressant in some countries, but not in the USA. It is approved in the USA and some other countries as a treatment for fibromyalgia. It has few pharmacokinetic and pharmacodynamic interactions with other drugs. Milnacipran has a half-life of about 10 h and therefore needs to be administered twice per day. It is metabolized by CYP3A4, but the major pathway for clearance is direct conjugation and renal elimination. As with other drugs in this class, dysuria is a common, troublesome, and dose-dependent adverse effect (occurring in up to 7% of patients). High-dose milnacipran has been reported to cause blood pressure and pulse elevations. Levomilnacipran is the levorotary enantiomer of milnacipran, and it is pharmacologically very similar to the racemic compound, although the side effects may be milder within the approved dosing range. As with other NE uptake inhibitors, it may increase blood pressure and pulse, although it appears to do so less than some other medications. All medications in the class can cause serotonin syndrome when combined with MAOIs.

Antidepressants inhibit Nav1.3, Nav1.7, and Nav1.8 neuronal voltage-gated sodium channels more potently than Nav1.2 and Nav1.6 channels expressed in Xenopus oocytes

Tricyclic antidepressants (TCAs) and duloxetine are used to treat neuropathic pain. However, the mechanisms underlying their analgesic effects remain unclear. Although many investigators have shown inhibitory effects of antidepressants on voltage-gated sodium channels (Na_v) as a possible mechanism of analgesia, to our knowledge, no one has compared effects on the diverse variety of sodium channel α subunits. We investigated the effects of antidepressants on sodium currents in Xenopus oocytes expressing Na_v1.2, Na_v1.3, Na_v1.6, Na_v1.7, and Na_v1.8 with a β₁ subunit by using whole-cell, two-electrode, voltage clamp techniques. We also studied the role of the β₃ subunit on the effect of antidepressants on Na_v1.3. All antidepressants inhibited sodium currents in an inactivated state induced by all five α subunits with β₁. The inhibitory effects were more potent for Na_v1.3, Na_v1.7, and Na_v1.8, which are distributed in dorsal root ganglia, than Na_v1.2 and Na_v1.6, which are distributed primarily in the central nervous system. The effect of amitriptyline on Na_v1.7 with β₁ was most potent with a half-maximal inhibitory concentration (IC₅₀) 4.6 μmol/L. IC₅₀ for amitriptyline on Na_v1.3 coexpressed with β₁ was lowered from 8.4 to 4.5 μmol/L by coexpression with β₃. Antidepressants predominantly inhibited the sodium channels expressed in dorsal root ganglia, and amitriptyline has the most potent inhibitory effect. This is the first evidence, to our knowledge, showing the diverse effects of antidepressants on various α subunits. Moreover, the β₃ subunit appears important for inhibition of Na_v1.3. These findings may aid better understanding of the mechanisms underlying the pain relieving effects of antidepressants.

Spinal Disinhibition in Experimental and Clinical Painful Diabetic Neuropathy

Impaired rate-dependent depression (RDD) of the Hoffman reflex is associated with reduced dorsal spinal cord potassium chloride cotransporter expression and impaired spinal γ-aminobutyric acid type A receptor function, indicative of spinal inhibitory dysfunction. We have investigated the pathogenesis of impaired RDD in diabetic rodents exhibiting features of painful neuropathy and the translational potential of this marker of spinal inhibitory dysfunction in human painful diabetic neuropathy. Impaired RDD and allodynia were present in type 1 and type 2 diabetic rats but not in rats with type 1 diabetes receiving insulin supplementation that did not restore normoglycemia. Impaired RDD in diabetic rats was rapidly normalized by spinal delivery of duloxetine acting via 5-hydroxytryptamine type 2A receptors and temporally coincident with the alleviation of allodynia. Deficits in RDD and corneal nerve density were demonstrated in patients with painful diabetic neuropathy compared with healthy control subjects and patients with painless diabetic neuropathy. Spinal inhibitory dysfunction and peripheral small fiber pathology may contribute to the clinical phenotype in painful diabetic neuropathy. Deficits in RDD may help identify patients with spinally mediated painful diabetic neuropathy who may respond optimally to therapies such as duloxetine.

Effects of subthalamic deep brain stimulation with duloxetine on mechanical and thermal thresholds in 6OHDA lesioned rats

Chronic pain is the most common non-motor symptom of Parkinson's disease (PD) and is often overlooked. Unilateral 6-hydroxydopamine (6-OHDA) medial forebrain bundle lesioned rats used as models for PD exhibit decreased sensory thresholds in the left hindpaw. Subthalamic deep brain stimulation (STN DBS) increases mechanical thresholds and offers improvements with chronic pain in PD patients. However, individual responses to STN high frequency stimulation (HFS) in parkinsonian rats vary with 58% showing over 100% improvement, 25% showing 30-55% improvement, and 17% showing no improvement. Here we augment STN DBS by supplementing with a serotonin-norepinephrine reuptake inhibitor commonly prescribed for pain, duloxetine. Duloxetine was administered intraperitoneally (30mg/kg) in 15 parkinsonian rats unilaterally implanted with STN stimulating electrodes in the lesioned right hemisphere. Sensory thresholds were tested using von Frey, Randall-Selitto and hot-plate tests with or without duloxetine, and stimulation to the STN at HFS (150Hz), low frequency (LFS, 50Hz), or off stimulation. With HFS or LFS alone (left paw; p=0.016; p=0.024, respectively), animals exhibited a higher mechanical thresholds stable in the three days of testing, but not with duloxetine alone (left paw; p=0.183). Interestingly, the combination of duloxetine and HFS produced significantly higher mechanical thresholds than duloxetine alone (left paw, p=0.002), HFS alone (left paw, p=0.028), or baseline levels (left paw; p<0.001). These findings show that duloxetine paired with STN HFS increases mechanical thresholds in 6-OHDA-lesioned animals more than either treatment alone. It is possible that duloxetine augments STN DBS with a central and peripheral additive effect, though a synergistic mechanism has not been excluded.

Duloxetine Inhibits Microglial P2X4 Receptor Function and Alleviates Neuropathic Pain after Peripheral Nerve Injury

P2X4 receptors (P2X4R) are a family of ATP-gated non-selective cation channels. We previously demonstrated that activation of P2X4R in spinal microglia is crucial for neuropathic pain, a highly debilitating chronic pain condition, suggesting that P2X4R is a potential therapeutic target for treating neuropathic pain. Thus, the identification of a compound that has a potent inhibitory effect on P2X4R is an important clinical challenge. In the present study, we screened a chemical library of clinically approved drugs and show for the first time that duloxetine, a serotonin and noradrenaline reuptake inhibitor, has an inhibitory effect on rodent and human P2X4R. In primary cultured microglial cells, duloxetine also inhibited P2X4R-, but not P2X7R-, mediated responses. Moreover, intrathecal administration of duloxetine in a model of neuropathic pain produced a reversal of nerve injury-induced mechanical allodynia, a cardinal symptom of neuropathic pain. In rats that were pretreated with a serotonin-depleting agent and a noradrenaline neurotoxin, the antiallodynic effect of duloxetine was reduced, but still remained. Based on these results, we suggest that, in addition to duloxetine’s primary inhibitory action on serotonin and noradrenaline transporters, an inhibitory effect on P2X4R may be involved at least in part in an antiallodynic effect of intrathecal duloxetine in a model of neuropathic pain.

Small Molecule Agonists of Cell Adhesion Molecule L1 Mimic L1 Functions In Vivo

Lack of permissive mechanisms and abundance of inhibitory molecules in the lesioned central nervous system of adult mammals contribute to the failure of functional recovery after injury, leading to severe disabilities in motor functions and pain. Peripheral nerve injury impairs motor, sensory, and autonomic functions, particularly in cases where nerve gaps are large and chronic nerve injury ensues. Previous studies have indicated that the neural cell adhesion molecule L1 constitutes a viable target to promote regeneration after acute injury. We screened libraries of known drugs for small molecule agonists of L1 and evaluated the effect of hit compounds in cell-based assays in vitro and in mice after femoral nerve and spinal cord injuries in vivo. We identified eight small molecule L1 agonists and showed in cell-based assays that they stimulate neuronal survival, neuronal migration, and neurite outgrowth and enhance Schwann cell proliferation and migration and myelination of neurons in an L1-dependent manner. In a femoral nerve injury mouse model, enhanced functional regeneration and remyelination after application of the L1 agonists were observed. In a spinal cord injury mouse model, L1 agonists improved recovery of motor functions, being paralleled by enhanced remyelination, neuronal survival, and monoaminergic innervation, reduced astrogliosis, and activation of microglia. Together, these findings suggest that application of small organic compounds that bind to L1 and stimulate the beneficial homophilic L1 functions may prove to be a valuable addition to treatments of nervous system injuries.

Pharmacological modulation of pulvinar resting-state regional oscillations and network dynamics in major depression

The pulvinar, the largest thalamus nucleus, has rich anatomical connections with several different cortical and subcortical regions suggesting its important involvement in high-level cognitive and emotional functions. Unfortunately, pulvinar dysfunction in psychiatric disorders particularly major depression disorder has not been thoroughly examined to date. In this study we explored the alterations in the baseline regional and network activities of the pulvinar in MDD by applying spectral analysis of resting-state oscillatory activity, functional connectivity and directed (effective) connectivity on resting-state fMRI data acquired from 20 healthy controls and 19 participants with MDD. Furthermore, we tested how pharmacological treatment with duloxetine can modulate the measured local and network variables in ten participants who completed treatment. Our results revealed a frequency-band dependent modulation of power spectrum characteristics of pulvinar regional oscillatory activity. At the network level, we found MDD is associated with aberrant causal interactions between pulvinar and several systems including default-mode and posterior insular networks. It was also shown that duloxetine treatment can correct or overcompensate the pathologic network behavior of the pulvinar. In conclusion, we suggest that pulvinar regional baseline oscillatory activity and its resting-state network dynamics are compromised in MDD and can be modulated therapeutically by pharmacological treatment.

Central Sensitization and Neuropathic Features of Ongoing Pain in a Rat Model of Advanced Osteoarthritis

Osteoarthritis (OA) pain is most commonly characterized by movement-triggered joint pain. However, in advanced disease, OA pain becomes persistent, ongoing and resistant to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs). The mechanisms underlying ongoing pain in advanced OA are poorly understood. We recently showed that intra-articular (i.a.) injection of monosodium iodoacetate (MIA) into the rat knee joint produces concentration-dependent outcomes. Thus, a low dose of i.a. MIA produces NSAID-sensitive weight asymmetry without evidence of ongoing pain and a high i.a. MIA dose produces weight asymmetry and NSAID-resistant ongoing pain. In the present study, palpation of the ipsilateral hind limb of rats treated 14 days previously with high, but not low, doses of i.a. MIA produced expression of the early oncogene, FOS, in the spinal dorsal horn. Inactivation of descending pain facilitatory pathways using a microinjection of lidocaine within the rostral ventromedial medulla induced conditioned place preference selectively in rats treated with the high dose of MIA. Conditioned place preference to intra-articular lidocaine was blocked by pretreatment with duloxetine (30 mg/kg, intraperitoneally at -30 minutes). These observations are consistent with the likelihood of a neuropathic component of OA that elicits ongoing, NSAID-resistant pain and central sensitization that is mediated, in part, by descending modulatory mechanisms. This model provides a basis for exploration of underlying mechanisms promoting neuropathic components of OA pain and for the identification of mechanisms that might guide drug discovery for treatment of advanced OA pain without the need for joint replacement.

PERSPECTIVE

Difficulty in managing advanced OA pain often results in joint replacement therapy in these patients. Improved understanding of mechanisms driving NSAID-resistant ongoing OA pain might facilitate development of alternatives to joint replacement therapy. Our findings suggest that central sensitization and neuropathic features contribute to NSAID-resistant ongoing OA joint pain.

Effects of duloxetine on microRNA expression profile in frontal lobe and hippocampus in a mouse model of depression

Depression is a major mood disorder affecting people worldwide. The posttranscriptional gene regulation mediated by microRNAs (miRNAs) which may have critical roles in the pathogenesis of depression. However, to date, little is known about the effects of the antidepressant drug duloxetine on miRNA expression profile in chronic unpredictable mild stress (CUMS)-induced depression model in mice. Healthy adult male Kunming mice were randomly divided into three groups: control group, model group and duloxetine group. Sucrose preference test and open field test were used to represent the behavioral change. MiRNAs levels in frontal lobe and hippocampus of mice were analyzed using miRNA microarrays assay. We observed that long-term treatment with duloxetine significantly ameliorated the CUMS procedure-induced sucrose preference decreases and mice treated with duloxetine demonstrated a reversal of the number of crossings, and rearings reduced by CUMS. A significant upregulation of miR-132 and miR-18a in hippocampus in the duloxetine treatment group compared with model group, whereas the levels of miR-134 and miR-124a were significantly downregulated. Furthermore, miR-18a showed significant upregulation in frontal lobe in the duloxetine treatment group relative to model group. Our data showed that miRNA expression profile in frontal lobe and hippocampus was affected by duloxetine in mice model of depression. The effect was especially pronounced in the hippocampus, suggesting that hippocampus might be the action site of duloxetine, which presumably worked by regulating the expression of miRNA levels.

Adolescent social isolation increases anxiety-like behavior and ethanol intake and impairs fear extinction in adulthood: Possible role of disrupted noradrenergic signaling

Alcohol use disorder, anxiety disorders, and post-traumatic stress disorder (PTSD) are highly comorbid, and exposure to chronic stress during adolescence may increase the incidence of these conditions in adulthood. Efforts to identify the common stress-related mechanisms driving these disorders have been hampered, in part, by a lack of reliable preclinical models that replicate their comorbid symptomatology. Prior work by us, and others, has shown that adolescent social isolation increases anxiety-like behaviors and voluntary ethanol consumption in adult male Long-Evans rats. Here we examined whether social isolation also produces deficiencies in extinction of conditioned fear, a hallmark symptom of PTSD. Additionally, as disrupted noradrenergic signaling may contribute to alcoholism, we examined the effect of anxiolytic medications that target noradrenergic signaling on ethanol intake following adolescent social isolation. Our results confirm and extend previous findings that adolescent social isolation increases anxiety-like behavior and enhances ethanol intake and preference in adulthood. Additionally, social isolation is associated with a significant deficit in the extinction of conditioned fear and a marked increase in the ability of noradrenergic therapeutics to decrease ethanol intake. These results suggest that adolescent social isolation not only leads to persistent increases in anxiety-like behaviors and ethanol consumption, but also disrupts fear extinction, and as such may be a useful preclinical model of stress-related psychopathology. Our data also suggest that disrupted noradrenergic signaling may contribute to escalated ethanol drinking following social isolation, thus further highlighting the potential utility of noradrenergic therapeutics in treating the deleterious behavioral sequelae associated with early life stress.

Early effects of duloxetine on emotion recognition in healthy volunteers

The serotonin-noradrenaline reuptake inhibitor (SNRI) duloxetine is an effective treatment for major depression and generalised anxiety disorder. Neuropsychological models of antidepressant drug action suggest therapeutic effects might be mediated by the early correction of maladaptive biases in emotion processing, including the recognition of emotional expressions. Sub-chronic administration of duloxetine (for two weeks) produces adaptive changes in neural circuitry implicated in emotion processing; however, its effects on emotional expression recognition are unknown. Forty healthy participants were randomised to receive either 14 days of duloxetine (60 mg/day, titrated from 30 mg after three days) or matched placebo (with sham titration) in a double-blind, between-groups, repeated-measures design. On day 0 and day 14 participants completed a computerised emotional expression recognition task that measured sensitivity to the six primary emotions. Thirty-eight participants (19 per group) completed their course of tablets and were included in the analysis. Results provide evidence that duloxetine, compared to placebo, may reduce the accurate recognition of sadness. Drug effects were driven by changes in participants' ability to correctly detect subtle expressions of sadness, with greater change observed in the placebo relative to the duloxetine group. These effects occurred in the absence of changes in mood. Our preliminary findings require replication, but complement recent evidence that sadness recognition is a therapeutic target in major depression, and a mechanism through which SNRIs could resolve negative biases in emotion processing to achieve therapeutic effects.