We, therefore, concluded that the observed negative chronotropic effect results from OR51E1 activation

ductions in coronary perfusion. The absence of coronary coupling to ventricular activity, described by us in this and other models, suggests additional coronary dysregulation. Multiple paths/mediators regulating angiogenesis were also sensitive to A 2A R KO in endotoxemic heart, including shifts in VEGF, HIF-1, angiopoietin, TGF-, GM-CSF, PDGF and IGF-1 pathways and key regulatory molecules . While the A2B receptor is more broadly implicated in control of angiogenesis, these changes suggest A2A R-dependent processes may influence angiogenesis in the context of uncontrolled inflammation. RT-qPCR confirmation of microarray-detected responses Data confirm agreement between transcript expression determined via RT-qPCR and microarray methods, with PCR further highlighting distinct transcriptional effects of A2A R KO: in some cases, KO eliminates responses to LPS; alters baseline yet not LPSdependent expression; enhances induction or repression in response to vehicle and LPS or reduces gene expression in the vehicle group while negating further changes with LPS. Confirming PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19801058 the microarray approach, some of these responses are also functionally relevant. For example, Txnip encodes a stress-responsive protein inhibiting the anti-oxidant/signalling molecule thioredoxin. Reductions in TXNIP inhibit vascular inflammation and TNF- signalling, TXNIP dysregulation promotes inflammatory disease and elevations in TXNIP facilitate apoptosis. Inhibition of Txnip induction by A2AR activity may thus enhance protective thioredoxin functionality. Study limitations Several study limitations are worth noting. While essential genesis of cardiac injury is studied and understood within the in situ organ, this entails experimental limitations inherent to in vivo studies of organ dysfunction in sepsis/ endotoxemia. Organ injury in these settings not only involves intrinsic organ-specific mechanisms but also influenced by extrinsic factors, including shifts in systemic inflammation, haemodynamics and neuroendocrine influences. Although we assess the intrinsic myocardial dysfunction in ex vivo tissue, we cannot isolate potential influences of A2AR KO on cardiac loading, neurohumoral factors or indeed systemic inflammation. That said, while A2AR KO augmented some inflammatory markers, systemic and cardiac cytokine responses were largely insensitive to KO and the myocardial response was very selectively modified, MedChemExpress AGI-5198 indicating distinct effects of A2AR activity on cardiac injury processes. We are also unable to detail cell-specific origins of myocardial transcriptional changes. Migrating inflammatory cells could influence the transcriptomic profile for intact myocardium, though, as detailed in the Supplementary material, the expression profile of endotoxemic myocardial tissue is inconsistent with major contamination from such cells. An added limitation relates to the intriguing observation of both age- and sex-dependent mortality effects of LPS and A2ARs. This unfortunately precluded any detailed interrogation of these outcomes 46 Purinergic Signalling 13:2749 due to poor survival in older KO mice. Future work might focus specifically on responses to LPS/sepsis in clinically relevant aged cohorts, correlating age-dependent transcriptomic and phenotypic outcomes. Finally, while profound transcriptional changes observed in the current profiling study are predicted to translate to functionally relevant protein changes, this exploratory analysis does not directly confirm altere