Caffeine, a nonspecific adenosine receptor (AR) antagonist is widely used to treat apnea of prematurity. Because adenosine modulates multiple biologic processes including inflammation, we hypothesized that AR blockade by caffeine would increase cytokine release from neonatal monocytes. Using cord blood monocytes (CBM), we investigated 1) the changes in AR mRNA profile by real time quantitative reverse-transcription polymerase-chain-reaction (qRT-PCR) and protein expression (western blot) after in vitro culture, caffeine or lipopolysaccharide (LPS) exposure, and 2) the modulation of cytokine release and cyclic adenosine monophosphate (cAMP) production by enzyme-linked immunosorbent assay (ELISA) induced by caffeine and specific AR antagonists: DPCPX(A 1 R), ZM241385(A 2a R), MRS1754(A 2b R), and MRS1220(A 3 R). After 48 h in culture, A 2a R and A 2b R gene expression increased 1.9 (p ϭ 0.04) and 2.5-fold (p ϭ 0.003), respectively. A 1 R protein expression directly correlated with increasing LPS concentrations (p ϭ 0.01), with minimal expression preexposure. Only caffeine (50 M) and DPCPX (10 nM) decreased tumor necrosis factor-alpha (TNF-␣) release from LPS activated-CBM by 20 and 25% (p ϭ 0.01) and TNF-␣ gene expression by 30 and 50%, respectively, in conjunction with a Ն2-fold increase in cAMP (p Ͻ 0.05). AR blockade did not modulate other measured cytokines. The induction of A 1 R after LPS exposure suggests an important role of this receptor in the control of inflammation in neonates. Our findings also suggest that caffeine, via A 1 R blockade, increases cAMP production and inhibits pretranscriptional TNF-␣ production by CBM. (Pediatr Res 65: 203-208, 2009) C affeine (1,3,11 trimethylxantine) is a stimulant widely used in neonatology to treat apnea of prematurity (1). At therapeutic range (5 to 15 g/mL), caffeine blocks A 1 and A 2a adenosine receptors (ARs) stimulating ventilation (2-4). Recently, caffeine has also been linked to a decrease in the incidence of bronchopulmonary dysplasia and cerebral palsy in extremely premature infants (5,6), although the mechanisms explaining these findings have not been elucidated.The natural ligand for ARs, adenosine, has a crucial role in multiple biologic processes including inflammation (7,8). The increase in tumor necrosis factor-alpha (TNF-␣) release by adult peripheral blood monocytes (PBM) in response to lipopolysaccharide (LPS) exposure can be abolished by pretreatment with A 2a R agonists (9,10). Adenosine binding to A 1 R (11,12) and A 3 R (13,14) also modulates TNF-␣ release from adult monocytes, whereas A 2b R appears to have little effect (10).Little is known about AR expression on neonatal monocytes and the role of caffeine in modulating cytokine release. We hypothesized that caffeine blockade of ARs on neonatal monocytes would increase the release of cytokines in response to LPS. To test this hypothesis, we used cord blood monocytes (CBM) from full-term infants to 1) characterize the changes in AR mRNA profile and protein expression after 48 h in ...

Synaptic activity can modify expression of neurotrophins, which influence the development of neuronal circuits. In the newborn rat, early hyperoxia silences the synaptic activity and input from the carotid body, impairing the development and function of chemoreceptors. The purpose of this study was to determine whether early hyperoxic exposure, sufficient to induce hypoplasia of the carotid body and decrease the number of chemoafferents, would also modify neurotrophin expression within the nucleus tractus solitarii (nTS). Rat pups were exposed to hyperoxia (fraction of inspired oxygen 0.60) or normoxia until 7 or 14 days of postnatal development (PND). In the carotid body, hyperoxia decreased brain-derived neurotrophic factor (BDNF) protein expression by 93% (P = 0.04) after a 7-day exposure, followed by a decrease in retrogradely labeled chemoafferents by 55% (P = 0.004) within the petrosal ganglion at 14 days. Return to normoxia for 1 wk after a 14-day hyperoxic exposure did not reverse this effect. In the nTS, hyperoxia for 7 days: 1) decreased BDNF gene expression by 67% and protein expression by 18%; 2) attenuated upregulation of BDNF mRNA levels in response to acute hypoxia; and 3) upregulated p75 neurotrophic receptor, truncated tropomyosin kinase B (inactive receptor), and cleaved caspase-3. These effects were not observed in the locus coeruleus (LC). Hyperoxia for 14 days also decreased tyrosine hydroxylase levels by 18% (P = 0.04) in nTS but not in the LC. In conclusion, hyperoxic exposure during early PND reduces neurotrophin levels in the carotid body and the nTS and shifts the balance of neurotrophic support from prosurvival to proapoptotic in the nTS, the primary brain stem site for central integration of sensory and autonomic inputs.

Objective To determine changes in cytokine levels associated with caffeine treatment in a cohort of preterm infants. Study design For this observational prospective study, we collected clinical data from 26 preterm infants (≤30 weeks gestational age). In addition to caffeine levels, cytokine profiles in peripheral blood (PB) and tracheal aspirates (TA) were determined with enzyme-linked immunosorbent assay at birth, before and after (at 24 hours and 1 week) initiation of caffeine. Non-parametric statistics were applied. Results Included infants were 26.9 1.7 weeks gestational age and weighed 985 ± 202 g. At birth, all cytokine concentrations were significantly greater in TA than PB. Serum caffeine levels were 11.1 μg/mL (interquartile range, 1.85) at approximately 24 hours post-load and 16.4 (8.7) μg/mL at 1 week on treatment. At approximately 24 hours post-load, interleukin (IL)-10 levels decreased by 47.5% (P = .01) in PB and 38.5% (P = .03) in TA, whereas other cytokine levels remained unchanged. At 1 week, caffeine levels were correlated (U-shaped) with changes in proinflammatory tumor necrosis factor-α (R2 = 0.65; P = .0008), interleukin (IL)-1β (R2 = 0.73; P = .0007), and IL-6 (R2 = 0.59; P = .003), whereas inversely correlated (linear) with the anti-inflammatory IL-10 (R2 = 0.64; P = .0008). Altogether, caffeine, at serum levels ≥20 μg/mL, was associated with a proinflammatory profile after 1 week of treatment. Conclusions Caffeine treatment for apnea of prematurity correlates with changes in cytokine profile. Caffeine levels ≥20 μg/mL are associated with a proinflammatory profile in our cohort of preterm infants.