ATPace™: injectable adenosine 5'-triphosphate : Diagnostic and therapeutic indications

Discrimination of Ribonucleoside Mono-, Di-, and Triphosphates Using an Engineered Nanopore

Ribonucleotides, which widely exist in all living organisms and are essential to both physiological and pathological processes, can naturally appear as ribonucleoside mono-, di-, and triphosphates. Natural ribonucleotides can also dynamically switch between different phosphorylated forms, posing a great challenge for sensing. A specially engineered nanopore sensor is promising for full discrimination of all canonical ribonucleoside mono-, di-, and triphosphates. However, such a demonstration has never been reported, due to the lack of a suitable nanopore sensor that has a sufficient resolution. In this work, we utilized a phenylboronic acid (PBA) modified Mycobacterium smegmatis porin A (MspA) hetero-octamer for ribonucleotide sensing. Twelve types of ribonucleotides, including mono-, di-, and triphosphates of cytidine (CMP, CDP, CTP), uridine (UMP, UDP, UTP), adenosine (AMP, ADP, ATP), and guanosine (GMP, GDP, GTP) were simultaneously discriminated. A machine-learning algorithm was also developed, which achieved a general accuracy of 99.9% for ribonucleotide sensing. This strategy was also further applied to identify ribonucleotide components in ATP tablets and injections. This sensing strategy provides a direct, accurate, easy, and rapid solution to characterize ribonucleotide components in different phosphorylated forms.

Historical and Current Adenosine Receptor Agonists in Preclinical and Clinical Development

Adenosine receptors (ARs) function in the body’s response to conditions of pathology and stress associated with a functional imbalance, such as in the supply and demand of energy/oxygen/nutrients. Extracellular adenosine concentrations vary widely to raise or lower the basal activation of four subtypes of ARs. Endogenous adenosine can correct an energy imbalance during hypoxia and other stress, for example, by slowing the heart rate by A₁AR activation or increasing the blood supply to heart muscle by the A_2AAR. Moreover, exogenous AR agonists, antagonists, or allosteric modulators can be applied for therapeutic benefit, and medicinal chemists working toward that goal have reported thousands of such agents. Thus, numerous clinical trials have ensued, using promising agents to modulate adenosinergic signaling, most of which have not succeeded. Currently, short-acting, parenteral agonists, adenosine and Regadenoson, are the only AR agonists approved for human use. However, new concepts and compounds are currently being developed and applied toward preclinical and clinical evaluation, and initial results are encouraging. This review focuses on key compounds as AR agonists and positive allosteric modulators (PAMs) for disease treatment or diagnosis. AR agonists for treating inflammation, pain, cancer, non-alcoholic steatohepatitis, angina, sickle cell disease, ischemic conditions and diabetes have been under development. Multiple clinical trials with two A₃AR agonists are ongoing.

Historical and Current Adenosine Receptor Agonists in Preclinical and Clinical Development

Adenosine receptors (ARs) function in the body's response to conditions of pathology and stress associated with a functional imbalance, such as in the supply and demand of energy/oxygen/nutrients. Extracellular adenosine concentrations vary widely to raise or lower the basal activation of four subtypes of ARs. Endogenous adenosine can correct an energy imbalance during hypoxia and other stress, for example, by slowing the heart rate by A₁AR activation or increasing the blood supply to heart muscle by the A_2AAR. Moreover, exogenous AR agonists, antagonists, or allosteric modulators can be applied for therapeutic benefit, and medicinal chemists working toward that goal have reported thousands of such agents. Thus, numerous clinical trials have ensued, using promising agents to modulate adenosinergic signaling, most of which have not succeeded. Currently, short-acting, parenteral agonists, adenosine and Regadenoson, are the only AR agonists approved for human use. However, new concepts and compounds are currently being developed and applied toward preclinical and clinical evaluation, and initial results are encouraging. This review focuses on key compounds as AR agonists and positive allosteric modulators (PAMs) for disease treatment or diagnosis. AR agonists for treating inflammation, pain, cancer, non-alcoholic steatohepatitis, angina, sickle cell disease, ischemic conditions and diabetes have been under development. Multiple clinical trials with two A₃AR agonists are ongoing.

Emergency department visits for paroxysmal supraventricular tachycardia in Saudi Arabia

PURPOSE

The present study aimed to compare the demographic, medical history, clinical features, and treatment management of paroxysmal supraventricular tachycardia (PSVT) in the emergency department of a teaching hospital in Riyadh, Saudi Arabia. A secondary purpose was to evaluate Adenosine response among numerous variables that might be used as predictors of the conversion.

METHODS

All PSVT cases presented to the Department of Emergency Medicine at King Khalid University Hospital, during the period from January 1, 2016, until December 31, 2016, were included in the study. Patients were assigned into two groups: adenosine sensitive (AS-group) and adenosine resistant (AR-group) according to adenosine conversion response.

RESULTS

A total of 38 patients were admitted during the study period. Fisher's exact test results showed that there were no significant (P > 0.05) differences among the AS-group and AR-group in the demographics, past medical history and clinical features, and post-ablation condition, except for the previous usage of the other anti-arrhythmic drugs to convert the last PSVT in the AR-group. The first bolus of adenosine had higher sensitivity and specificity, compared to the second bolus. Further, the second bolus of adenosine was not specific for short-term treatment of PSVT.

CONCLUSIONS

Differences in adenosine sensitivity among PSVT patients were independent of demographic, past medical history, and clinical features of PSVT patients. Thus, the difference in adenosine response among groups may be attributed to the heterozygosity in conducting pathways. The first bolus of adenosine had high sensitivity and specificity, compared to the second bolus, and their optimal levels were predictable by HR deceleration.

Syncope

Syncope is common representing approximately 3% of ED visits and up to 6% of hospital admissions, with a cost close to 2 billion dollars per year. Diagnostic testing is often poorly sensitive and evaluations commonly lack a standardized approach. A mindful and systematic approach can increase sensitivity and improve diagnostic accuracy. A thorough history and physical exam is paramount, as conclusions drawn from the history and exam will guide further assessment. Developing a strategy for the first and, if necessary, subsequent tests will improve the accuracy of identifying the etiology of syncope and reduce cost. Although syncope has a favorable prognosis, identification of patients with structural heart disease is critical, as these patients are at greatest risk for mortality. Several risk scoring systems have been developed to help separate high risk from low risk patients.

Syncope associated with documented paroxysmal atrioventricular block reproduced by adenosine 5' triphosphate injection

AIMS

We sought to investigate in patients with syncope the relationship between documented paroxysmal atrioventricular block (AVB) of unknown mechanism and AVB induced by adenosine triphosphate (ATP) injection.

METHODS AND RESULTS

We selected patients >45 years free of structural heart disease with syncope related to paroxysmal AVB documented by Holter or in-hospital monitoring, but without any trigger suggestive of vasovagal origin and with normal baseline electrocardiogram. Adenosine triphosphate test was performed according to the usual protocol. Nine patients (all females; mean age 66 ± 14.6 years; range: 48-81 years) matching the abovementioned criteria particularly documented spontaneous complete AVB with long ventricular pauses. Their mean QRS duration was 86.6 ± 14.1 ms and the mean PR interval was 161 ± 21.3 ms. In all patients, ATP induced a long ventricular pause related to AVB (mean duration 13.2 s; range from 7 to 56 s). After a mean follow-up duration of 42 ± 36 months, electrocardiogram (ECG) remained unchanged without progression to permanent AVB or appearance of intraventricular conduction disturbances.

CONCLUSION

Some patients, predominantly older females, with 'normal' heart and ECG, have syncope associated with spontaneous AVB of unknown origin reproduced during the ATP test. They do not develop permanent AVB during follow-up. This unusual behaviour could be interpreted as an abnormal susceptibility to ATP and these patients could be considered to have 'ATP-sensitive AVB'. In this subgroup of syncope patients ATP test is useful.

ATP induces mild hypothermia in rats but has a strikingly detrimental impact on focal cerebral ischemia

Ischemic stroke is a devastating condition lacking effective therapies. A promising approach to attenuate ischemic injury is mild hypothermia. Recent studies show that adenosine nucleotides can induce hypothermia in mice. The purpose of the present study was to test the hypothesis that adenosine 5'-triphosphate (ATP) induces mild hypothermia in rats and reduces ischemic brain injury. We found that intraperitoneal injections of ATP decreased core body temperature in a dose-dependent manner; the dose appropriate for mild hypothermia was 2 g/kg. When ATP-induced hypothermia was applied to stroke induced by middle cerebral artery occlusion, however, a neuroprotective effect was not observed. Instead, the infarct volume grew even larger in ATP-treated rats. This was accompanied by an increased rate of seizure events, hemorrhagic transformation, and higher mortality. Continuous monitoring of physiologic parameters revealed that ATP reduced heartbeat rate and blood pressure. ATP also increased blood glucose, accompanied by severe acidosis and hypocalcemia. Western blotting showed that ATP decreased levels of both phospho-Akt and total-Akt in the cortex. Our results reveal that, despite inducing hypothermia, ATP is not appropriate for protecting the brain against stroke. Instead, we show for the first time that ATP treatment is associated with exaggerated ischemic outcomes and dangerous systemic side effects.