Stimulation of central A1 adenosine receptors suppresses seizure and neuropathology in a soman nerve agent seizure rat model.

The current regimen for treating nerve agent poisoning does not sufficiently suppress the excitotoxic activity that causes severe brain damage, especially in cases where treatment is delayed and nerve agent-induced status epilepticus develops. New therapeutic targets are required to improve survivability and minimize neuropathology after irreversible acetylcholinesterase inactivation. Earlier studies have shown that systemic delivery of adenosine agonists decreases nerve agent lethality; however, the mechanism of protection remains to be understood. The primary aim of this study was to investigate the role of central adenosine receptor (AR) stimulation in neuroprotection by directly injecting (6)-cyclopentyladenosine (CPA), an adenosine agonist specific to the A1 receptor subtype (A1R), into the brain intracerebroventricularly (ICV) in a soman seizure rat model. In addition to general A1R stimulation, we hypothesized that bilateral micro-injection of CPA into the cholinergic basal forebrain (BF) could also suppress excitotoxic activity. The results from these studies demonstrated that centrally administered adenosine agonists are anti-seizure and neuroprotective. CPA-delivered ICV prevented seizure and convulsion in 100% of the animals. Moreover, neuropathological evaluation indicated that adenosine treatments reduced brain damage from severe to minimal. Inhibition of the BF via CPA had varied results. Some animals were protected by treatment; however, others displayed similar pathology to the control. Overall, these data suggest that stimulating central ARs could be an effective target for the next generation countermeasures for nerve agent intoxication.

In Vivo Evaluation of A1 Adenosine Agonists as Novel Anticonvulsant Medical Countermeasures to Nerve Agent Intoxication in a Rat Soman Seizure Model.

Organophosphorus nerve agents (NAs) irreversibly inhibit acetylcholinesterase, which results in the accumulation of acetylcholine and widespread excitotoxic seizure activity. Because current medical countermeasures (anticholinergics, AChE reactivators, and benzodiazepines) lack sufficient anti-seizure efficacy when treatment is delayed, those intoxicated are at risk for severe brain damage or death if treatment is not immediately available. Toward developing a more effective anti-seizure treatment for NA intoxication, this study evaluated the efficacy of A1 adenosine (ADO) receptor (A1AR) agonists in a rat soman seizure model. One minute after exposure to soman (1.6 × LD50, subcutaneous), rats were treated intraperitoneally with one of the following agonists at increasing dose levels until anti-seizure efficacy was achieved: N6-cyclopentaladenosine (CPA), 2-chloro-N6-cyclopentyladenosine (CCPA), and (±)-5'-chloro-5'-deoxy-ENBA (ENBA). All A1AR agonists were efficacious in preventing seizure and promoting survival. The effective doses for the A1AR agonists were 60 mg/kg CPA, 36 mg/kg CCPA, and 62 mg/kg ENBA. Whereas vehicle-treated rats experienced 100% seizure and 21% survival (N = 28), ADO treatments reduced seizure occurrence and improved survival rates: 8% seizure and 83% survival with CPA (60 mg/kg, N = 12), 17% seizure and 75% survival with CCPA (36 mg/kg, N = 12), and 8% seizure, 83% survival with ENBA (62 mg/kg, N = 12). The brains of ADO-treated rats were also protected from damage as indicated by neurohistopathological analysis. While all ADO agonists provided neuroprotection, rats receiving CCPA and ENBA experienced less severe ADO-induced side effects (e.g., sedation, hypothermia, bradycardia) than with CPA. The data from this study suggest that the ADO signaling pathway is a promising mechanism for countering seizure activity induced by NAs.

N-acylhydrazone derivative ameliorates monocrotaline-induced pulmonary hypertension through the modulation of adenosine AA2R activity.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a disease that results in right ventricular (RV) dysfunction. While pulmonary vascular disease is the primary pathological focus, RV hypertrophy and RV dysfunction are the major determinants of prognosis in PAH. The aim of this study was to investigate the effects of (E)-N'-(3,4-dimethoxybenzylidene)-4-methoxybenzohydrazide (LASSBio-1386), an N-acylhydrazone derivative, on the lung vasculature and RV dysfunction induced by experimental PAH. METHODS: Male Wistar rats were injected with a single dose (60mg/kg, i.p.) of monocrotaline (MCT) and given LASSBio-1386 (50mg/kg, p.o.) or vehicle for 14 days. The hemodynamic, exercise capacity (EC), endothelial nitric oxide synthase (eNOS), adenosine A2A receptor (A2AR), sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a), phospholamban (PLB) expression, Ca(2+)-ATPase activity and vascular activity of LASSBio-1386 were evaluated. RESULTS AND CONCLUSIONS: The RV systolic pressure was elevated in the PAH model and reduced from 49.6 ± 5.0 mm Hg (MCT group) to 27.2 ± 2.1 mm Hg (MCT+LASSBio-1386 group; P<0.05). MCT administration also impaired the EC, increased the RV and pulmonary arteriole size, and promoted endothelial dysfunction of the pulmonary artery rings. In the PAH group, the eNOS, A2AR, SERCA2a, and PLB levels were changed compared with the control; in addition, the Ca(2+)-ATPase activity was reduced. These alterations were related with MCT-injected rats, and LASSBio-1386 had favorable effects that prevented the development of PAH. LASSBio-1386 is effective at preventing endothelial and RV dysfunction in PAH, a finding that may have important implications for ongoing clinical evaluation of A2AR agonists for the treatment of PAH.