Long-term xanthine therapy of asthma. Enprofylline and theophylline compared. International Enprofylline Study Group

Prioritizing Pain-Associated Targets with Machine Learning

While hundreds of genes have been associated with pain, much of the molecular mechanisms of pain remain unknown. As a result, current analgesics are limited to few clinically validated targets. Here, we trained a machine learning (ML) ensemble model to predict new targets for 17 categories of pain. The model utilizes features from transcriptomics, proteomics, and gene ontology to prioritize targets for modulating pain. We focused on identifying novel G-protein-coupled receptors (GPCRs), ion channels, and protein kinases because these proteins represent the most successful drug target families. The performance of the model to predict novel pain targets is 0.839 on average based on AUROC, while the predictions for arthritis had the highest accuracy (AUROC = 0.929). The model predicts hundreds of novel targets for pain; for example, GPR132 and GPR109B are highly ranked GPCRs for rheumatoid arthritis. Overall, gene-pain association predictions cluster into three groups that are enriched for cytokine, calcium, and GABA-related cell signaling pathways. These predictions can serve as a foundation for future experimental exploration to advance the development of safer and more effective analgesics.

Doxofylline is not just another theophylline!

Doxofylline, which differs from theophylline in containing the dioxalane group at position 7, has comparable efficacy to theophylline in the treatment of respiratory diseases, but with an improved tolerability profile and a favorable risk-to-benefit ratio. Furthermore, it does not have significant drug-drug interactions as exhibited with theophylline, which make using theophylline more challenging, especially in elderly patients with co-morbidities receiving multiple classes of drug. It is now clear that doxofylline also possesses a distinct pharmacological profile from theophylline (no significant effect on any of the known phosphodiesterase isoforms, no significant adenosine receptor antagonism, no direct effect on histone deacetylases, interaction with β₂-adrenoceptors) and therefore, should not be considered as just a modified theophylline. Randomized clinical trials of doxofylline to investigate the use of this drug to reduce exacerbations and hospitalizations due to asthma or COPD as an alternative to expensive biologics, and certainly as an alternative to theophylline are to be encouraged.

The association between asthma, asthma, therapeutic classes and hepatic enzyme elevation among adult HMO members

The results of this case-control study conducted at a large HMO support the notion that severe asthma may be associated with transient hepatic enzyme elevation. Conversely, we found no evidence of associations between asthma therapeutic classes and hepatic enzyme elevation.

Theophylline-induced recovery in a hemidiaphragm paralyzed by hemisection in rats: contribution of adenosine receptors

Previously, we demonstrated that a single intravenous injection of theophylline can induce recovery in a hemidiaphragm paralyzed by cervical (C2) spinal cord hemisection for up to 3 h. The present study contrasts the actions of enprofylline and theophylline on inducing hemidiaphragmatic recovery after cervical spinal cord hemisection. Both drugs are methylxanthines; however, theophylline is an adenosine receptor antagonist while enprofylline is not. To further test the involvement of adenosine receptors, N6 (L-2-phenylisopropyl) adenosine (L-PIA), an analogue of adenosine was used in conjunction with theophylline. Following a left C2 spinal cord hemisection, animals were injected with either enprofylline (2.5-20 mg/kg) or theophylline (15 mg/kg) alone or in combination. Theophylline-injected animals demonstrated robust respiratory-related activity in the previously quiescent left phrenic nerve and hemidiaphragm. No recovery was observed in any of the enprofylline-injected rats. When enprofylline injection was followed later with theophylline, recovery occurred. Prior L-PIA administration blocked theophylline-induced recovery. When given after theophylline, L-PIA attenuated and then blocked the induced activity in both the nerve and hemidiaphragm ipsilateral to spinal cord hemisection. We conclude that adenosine receptor antagonism is implicated in hemidiaphragmatic recovery after hemisection and theophylline may be useful in the treatment of spinal cord injured patients with respiratory deficits.

Canine mast cell adenosine receptors: cloning and expression of the A3 receptor and evidence that degranulation is mediated by the A2B receptor

We cloned and characterized the canine A3 adenosine receptor (AR) and examined AR-induced degranulation of the BR line of canine mastocytoma cells. Canine A3AR transcript is found predominantly in spleen, lung, liver, and testes and encodes a 314-amino acid heptahelical receptor. 125I-N6-Aminobenzyladenosine binds to two affinity states of canine A3AR with KD values of 0.7 +/- 0.1 and 16 +/- 0.8 nM, reflecting G protein-coupled and -uncoupled receptors, respectively. Xanthine antagonists bind with similar affinities to human, canine, and rabbit receptors but with 80-400-fold lower affinities to rat A3AR. Although canine BR mastocytoma cells contain A1AR, A2BAR, and A3AR, degranulation seems to be mediated primarily by A2BARs stimulated by the nonselective agonist 5'-N-ethylcarboxamidoadenosine (NECA) but not by the A3-selective agonist N6-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide. NECA-stimulated degranulation is not prevented by pertussis toxin and is blocked by enprofylline (Ki = 7 microM), an antiasthmatic xanthine with low affinity (Ki > 100 microM) for A1AR, A2AAR, and A3AR. NECA increases canine mastocytoma cell cAMP, Ca2+, and inositol trisphosphate levels; these responses are antagonized half-maximally by 7-15 microM enprofylline. The results suggest that (i) the cloned canine A3AR is structurally and pharmacologically more similar to human than to rat A3AR; (ii) the A2BAR, and not the A1AR or A3AR, is principally responsible for adenosine-mediated degranulation of canine BR mastocytoma cells; and (iii) the BR cell A2BAR couples to both Ca2+ mobilization and cAMP accumulation. Although A2B receptors play a major role in the regulation of BR mast cell degranulation, multiple AR subtypes and G proteins may influence mast cell functions.