Human safety study of a selective neuronal adenylate cyclase 1 inhibitor NB001 which relieves the neuropathic pain and blocks ACC in adult mice.

Calcium-dependent, neuronal adenylyl cyclase subtype 1 (AC1) is critical for cortical potentiation and chronic pain. NB001 is a first-in-class drug acting as a selective inhibitor against AC1. The present study delineated the pharmacokinetic (PK) properties of human-used NB001 (hNB001) formulated as immediate-release tablet. This first-in-human (FIH) study was designed as randomized, double-blind, placebo-controlled trial. hNB001 showed placebo-like safety and good tolerability in healthy volunteers. A linear dose-exposure relationship was demonstrated at doses between 20 mg and 400 mg. The relatively small systemic exposure of hNB001 in human showed low bioavailability of this compound through oral administration, which can be improved through future dosage research. Food intake had minimal impact on the absorption of hNB001 tablet. Animal experiments further confirmed that hNB001 had strong analgesic effect in animal models of neuropathic pain. In brain slice prepared from the anterior cingulate cortex (ACC), bath application of hNB001 blocked the induction of long-term potentiation (LTP). These results from both rodents and human strongly suggest that hNB001 can be safely used for the future treatment of different types of chronic pain in human patients.

Neuronal Adenylyl Cyclase Targeting Central Plasticity for the Treatment of Chronic Pain.

Chronic pain is a major health problem and the effective treatment for chronic pain is still lacking. The recent crisis created by the overuse of opioids for pain treatment has clearly shown the need for non-addictive novel pain medicine. Conventional pain medicines usually inhibit peripheral nociceptive transmission and reduce central transmission, especially pain-related excitatory transmission. For example, both opioids and gabapentin produce analgesic effects by inhibiting the release of excitatory transmitters and reducing neuronal excitability. Here, we will review recent studies of central synaptic plasticity contributing to central sensitization in chronic pain. Neuronal selective adenylyl cyclase subtype 1 (AC1) is proposed to be a key intracellular protein that causes both presynaptic and postsynaptic forms of long-term potentiation (LTP). Inhibiting the activity of AC1 by selective inhibitor NB001 blocks behavioral sensitization and injury-related anxiety in animal models of chronic pain. We propose that inhibiting injury-related LTPs will provide new mechanisms for designing novel medicines for the treatment of chronic pain and its related emotional disorders.

The Soluble Adenylyl Cyclase Inhibitor LRE1 Prevents Hepatic Ischemia/Reperfusion Damage Through Improvement of Mitochondrial Function.

Hepatic ischemia/reperfusion (I/R) injury is a leading cause of organ dysfunction and failure in numerous pathological and surgical settings. At the core of this issue lies mitochondrial dysfunction. Hence, strategies that prime mitochondria towards damage resilience might prove applicable in a clinical setting. A promising approach has been to induce a mitohormetic response, removing less capable organelles, and replacing them with more competent ones, in preparation for an insult. Recently, a soluble form of adenylyl cyclase (sAC) has been shown to exist within mitochondria, the activation of which improved mitochondrial function. Here, we sought to understand if inhibiting mitochondrial sAC would elicit mitohormesis and protect the liver from I/R injury. Wistar male rats were pretreated with LRE1, a specific sAC inhibitor, prior to the induction of hepatic I/R injury, after which mitochondria were collected and their metabolic function was assessed. We find LRE1 to be an effective inducer of a mitohormetic response based on all parameters tested, a phenomenon that appears to require the activity of the NAD+-dependent sirtuin deacylase (SirT3) and the subsequent deacetylation of mitochondrial proteins. We conclude that LRE1 pretreatment leads to a mitohormetic response that protects mitochondrial function during I/R injury.

Antinociceptive effects of the adenylyl cyclase inhibitor ST034307 on tooth-movement-induced nociception in rats.

OBJECTIVE: This study aimed to investigate the antinociceptive effects of the selective adenylyl cyclase type 1 (AC1) inhibitor ST034307 on tooth movement nociception through orofacial nociceptive behavior tests and molecular examination. METHODS: We placed fixed nickel-titanium alloy closed-coil springs around the incisors of male Sprague-Dawley rats to induce tooth movement. We subsequently administered ST034307 (3 mg/kg), for 2 days, intraperitoneally, and then subjected the rats to a battery of behavioral tests (n = 10/group) to assess orofacial nociception. The changes in the expression of key molecules in the anterior cingulate cortex were measured by ELISA (n = 8/group) and Western blotting (n = 8/group). RESULTS: Tooth movement increased face-grooming activities and rat grimace scale scores. Tooth movement was also associated with enhanced cyclic adenosine monophosphate (cAMP) generation as well as protein kinase A (PKA) activation. Moreover, the phosphorylation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and expression of N-methyl-d-aspartate (NMDA) receptors in the anterior cingulate cortex increased during tooth movement. ST034307 significantly decreased mouth wiping and rat grimace scale scores, accompanied by reductions in cAMP generation, PKA activation, AMPA receptor phosphorylation, and NMDA receptor expression in the anterior cingulate cortex. CONCLUSIONS: These results suggest that adenylyl cyclase type 1 plays an important role in the development of orthodontic tooth movement nociception. Furthermore, ST034307 can be used as an effective pharmacotherapy for orthodontic nociception.

Inhibition of Adenylyl Cyclase in the Spinal Cord Alleviates Painful Diabetic Neuropathy in Zucker Diabetic Fatty Rats.

OBJECTIVES: Diabetic neuropathy is the most common complication of both type 1 and type 2 diabetes. In this study, we tested the hypotheses that impaired Gi protein expression/function in the spinal cord is associated with the development of painful neuropathy in people with type 2 diabetes and that reduction of cyclic adenosine monophosphate (cAMP) production by inhibiting adenylyl cyclase in the spinal cord can alleviate diabetic neuropathy. METHODS: To this end, we examined the levels of cAMP, cAMP-dependent protein kinase (PKA) and cAMP response element-binding protein (CREB) in the spinal cord after the development of neuropathic pain in Zucker diabetic fatty (ZDF) rats with type 2 diabetes. We evaluated the effects of intrathecal injections of SQ22536, an adenylyl cyclase inhibitor, on mechanical allodynia and thermal hyperalgesia in rats with painful diabetic neuropathy. RESULTS: We found that diabetic ZDF rats exhibited mechanical allodynia and thermal hyperalgesia, which are associated with enhanced cAMP production, increased PKA activation and elevated CREB phosphorylation in the spinal cord. Additionally, diabetic ZDF rats exhibited attenuated expression of Giα, but not Gsα, in the spinal cord. Furthermore, intrathecal administrations of SQ22536 dose-dependently alleviated mechanical allodynia and thermal hyperalgesia in diabetic ZDF rats and reduced cAMP production, PKA activation and p-CREB expression in the spinal cord. CONCLUSIONS: Taken together, our study suggested that cAMP-mediated signalling in the spinal cord is likely critical for the development of painful neuropathy in people with type 2 diabetes.

The role of adenylyl cyclase in the medial prefrontal cortex in cocaine-induced behavioral sensitization in rats.

Repeated exposure to cocaine progressively increases drug-induced locomotor activity, which is termed behavioral sensitization. Previous research has demonstrated that in the medial prefrontal cortex (mPFC) modulation of cocaine-induced motor activity by agonists of Gi-coupled receptors, such as dopamine D2, GABAB and Group II metabotropic glutamate receptors, is reduced in sensitized animals, suggesting a loss in receptor function. Stimulation of each of these receptors acts in part to inhibit adenylyl cyclase activity, and thus, the formation of cAMP. The present studies tested the hypothesis that intra-mPFC inhibition of adenylyl cyclase by infusion of an inhibitor, SQ22536, could bypass the loss of inhibitory receptor function seen in this region, and thereby inhibit the expression of cocaine sensitization. Additional studies determined whether activation of mPFC adenylyl cyclase with NKH 477 could enhance the motor-stimulant response to cocaine. Initial studies demonstrated that cocaine-induced (15 mg/kg, i.p.) motor activity was dose-dependently reduced by injection of SQ22536 (5-75 nmol/side) into the mPFC, whereas NKH 477 (1.25-40 nmol/side) produced no significant effects. Additional studies showed that intra-mPFC injection of SQ22536 (50 nmol/side) attenuated the initiation of cocaine-induced behavioral sensitization and blocked the expression of sensitization following 1, 7 or 30 days of abstinence from cocaine. Also, intra-mPFC injection of NKH 477 enhanced cocaine-induced behavioral sensitization following 21 days of abstinence from cocaine. The results of the present study suggest modulation of adenylyl cyclase in the medial prefrontal cortex plays a key role in the expression of cocaine sensitization.