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Background/Objective: Pediatric neurocritical care survivorship is frequently accompanied by functional impairments. Lack of prognostic biomarkers is a barrier to early identification and management of impairment. We explored the association between blood biomarkers and functional impairment in children with acute acquired brain injury. Methods: This study is a secondary analysis of a randomized control trial evaluating early versus usual care rehabilitation in the pediatric intensive care unit (PICU). Forty-four children (17 [39%] female, median age 11 [interquartile range 6–13] years) with acute acquired brain injury admitted to the PICU were studied. A single center obtained serum samples on admission days 0, 1, 3, 5, and the day closest to hospital discharge. Biomarkers relevant to brain injury (neuron specific enolase [NSE], S100b), inflammation (interleukin [IL-6], C-reactive protein), and regeneration (brain-derived neurotrophic factor [BDNF], vascular endothelial growth factor [VEGF]) were collected. Biomarkers were analyzed using a Luminex® bioassay. Functional status scale (FSS) scores were abstracted from the medical record. New functional impairment was defined as a (worse) FSS score at hospital discharge compared to pre-PICU (baseline). Individual biomarker fluorescence index (FI) values for each sample collection day were correlated with new functional impairment using Spearman rank correlation coefficient (ρ). Trends in repeated measures of biomarker FI over time were explored graphically, and the association between repeated measures of biomarker FI and new functional impairment was analyzed using covariate adjusted linear mixed-effect models. Results: Functional impairment was inversely correlated with markers of regeneration and plasticity including BDNF at day 3 (ρ = − 0.404, p =.015), day 5 (ρ = − 0.549, p = 0.005) and hospital discharge (ρ = − 0.420, p = 0.026) and VEGF at day 1 (ρ = − 0.282, p = 0.008) and hospital discharge (ρ = − 0.378, p = 0.047), such that lower levels of both markers at each time point were associated with greater impairment. Similarly, repeated measures of BDNF and VEGF were inversely correlated with new functional impairment (B = − 0.001, p = 0.001 and B = − 0.001, p = 0.003, respectively). NSE, a biomarker of acute brain injury, showed a positive correlation between day 0 levels and new functional impairment (ρ = 0.320, p = 0.044). Conclusions: Blood-based biomarkers of regeneration and plasticity may hold prognostic utility for functional impairment among pediatric patients with neurocritical illness and warrant further investigation. [ABSTRACT FROM AUTHOR]

CD73 metabolizes extracellular 5'-AMP to adenosine; yet recent experiments in brain tissue suggest that CD73 is not required for the metabolism of 5'-AMP to adenosine because of tissue nonspecific alkaline phosphatase (TNAP), which like CD73 is a GPI-anchored ecto-enyzme with 5'-nucleotidase activity. Because adenosine importantly regulates renovascular function, we investigated whether both TNAP and CD73 are involved in the renovascular metabolism of 5=-AMP. To test this, we examined in isolated, perfused mouse kidneys the metabolism of 5'-AMP (applied to the lumen of the renal vasculature via intrarenal artery administration) to adenosine by measuring renal venous levels of 5'-AMP, adenosine, and inosine (adenosine metabolite) by mass spectrometry. In one study, we compared 5'-AMP metabolism in naive CD73/ (wild-type, n = 16) vs. CD73-/- (knockout, n = 16) kidneys; and in a second study, we compared 5=-AMP metabolism in CD73+/+ (n = 9) vs. CD73-/- (n = 8) kidneys pretreated with levamisole (1 mmol/l; TNAP inhibitor). In naive kidneys, 5'-AMP increased renal venous 5=-AMP, adenosine, and inosine, and these responses were similar in CD73+/+ vs. CD73-/- kidneys. Levamisole per se did not inhibit renovascular 5=-AMP metabolism; however, in the presence of levamisole, 5'-AMP increased renal venous 5=-AMP threefold more in CD73-/- vs. CD73+/+ kidneys and knockout of CD73 inhibited 5=-induced adenosine and inosine by 81 and 86%, respectively. TNAP mRNA, protein, and activity were similar in CD73+/+ vs. CD73-/- kidneys. In conclusion, CD73 and TNAP play interactive roles to metabolize luminally applied 5'-AMP in the renal vasculature such that inhibition of both is required to inhibit the production of adenosine. [ABSTRACT FROM AUTHOR]

Energy depletion increases the renal production of 2',3'-cAMP (a positional isomer of 3',5'- cAMP that opens mitochondrial permeability transition pores) and 2',3'-cAMP is converted to 2'-AMP and 3'-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this "2',3'-cAMP-adenosine pathway" are unknown, we examined whether 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) participates in the renal metabolism of 2',3'-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3',5'-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2',3'-cAMP to 2'-AMP. Infusions of 2',3'-cAMP into isolated CNPase wild-type (+/+) kidneys increasedrenal venous 2'-AMP, and this response was diminished by 63% in CNPase knockout (-/-) kidneys, whereas the conversion of 3',5'- cAMP to 5'-AMP was similar in CNPase +/+ vs. -/- kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2',3'- cAMP. In contrast, in CNPase -/- kidneys, energy depletion increased kidney tissue levels of 2',3'-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2',3'-cAMPadenosine pathway. [ABSTRACT FROM AUTHOR]

A1 receptors may participate in renal sympathetic neurotransmission by enhancing the postjunctional effects of norepinephrine. The purpose of this study was to test this concept using A1 receptor knockout (A1AR-/-) mice. In isolated kidneys from nontransgenic mice perfused with Tyrode's solution at a constant rate, renal sympathetic nerve stimulation (RSNS) increased (P = 0.0001) renal venous perfusate levels of inosine (adenosine metabolite) from 23.9 ± 3.7 to 32.7 ± 5.1, 68.2 ± 12.4, and 94.0 ± 14.3 ng/ml at 3, 5, and 7 Hz, respectively (n = 28), suggesting frequency-dependent production of adenosine. Conversely, RSNS decreased (P = 0.0001) renal venous perfusate levels of 5=-AMP (adenosine precursor) from 1.4 ± 0.3 to 1.1 ± 0.3, 0.80 ± 0.2, and 0.6 ± 0.2 ng/ml at 3, 5, and 7 Hz, respectively (n = 28), suggesting frequency-dependent increased metabolism of 5=-AMP. In kidneys from nontransgenic mice, blockade of adenosine receptors with 1,3-dipropyl-8-p-sulfophenylxanthine attenuated (P = 0.0130) vasoconstrictor responses to RSNS at 3, 5, and 7 Hz [control (n = 29): 22 ± 4, 34 ± 6, 42 ± 6 mmHg, respectively, 1,3-dipropyl-8-p-sulfophenylxanthine-treated (n = 11): 6 ± 1, 12 ± 3, 15 ± 3 mmHg, respectively]. In A1AR-/- kidneys (n = 10), vasoconstrictor responses to RSNS at 3, 5, and 7 Hz were 7 ± 3, 20 ± 5, and 36 ± 9 mmHg, respectively. In kidneys from wild-type littermates (n = 9), responses were 27 ± 9, 58 ± 14, and 59 ± 11 mmHg, respectively (effect of genotype: P = 0.0363). In kidneys from nontransgenic mice, 2-chloro-N6-cyclopentyladenosine (CCPA, highly selective A1 receptor agonist) increased renal vasoconstriction induced by norepinephrine (P = 0.0008; n = 28). In kidneys from A1AR-/- the response to norepinephrine was attenuated and the ability of CCPA to enhance responses to norepinephrine was abolished. In conclusion, adenosine formed during RSNS enhances the postjunctional effects of released norepinephrine by activating A1 receptors. [ABSTRACT FROM AUTHOR]

α-Synuclein is one of the most abundant proteins in presynaptic terminals. Normal expression of α-synuclein is essential for neuronal survival and it prevents the initiation of apoptosis in neurons through covalent cross-linking of cytochrome c released from mitochondria. Exocytosis of α-synuclein occurs with neuronal mitochondrial dysfunction, making its detection in cerebrospinal fluid (CSF) of children after severe traumatic brain injury (TBI) a potentially important marker of injury. Experimental therapeutic hypothermia (TH) improves mitochondrial function and attenuates cell death, and therefore may also affect CSF α-synuclein concentrations. We assessed α-synuclein levels in CSF of 47 infants and children with severe TBI using a commercial ELISA for detection of monomeric protein. 23 patients were randomized to TH based on published protocols where cooling (32-33°C) was initiated within 6-24 h, maintained for 48 h, and then followed by slow rewarming. CSF samples were obtained continuously via an intraventricular catheter for 6 days after TBI. Control CSF (n = 9) was sampled from children receiving lumbar puncture for CSF analysis of infection that was proven negative. Associations of initial Glasgow Coma Scale (GCS) score, age, gender, treatment, mechanism of injury and Glasgow Outcome Scale (GOS) score with CSF α-synuclein were compared by multivariate regression analysis. CSF α-synuclein levels were elevated in TBI patients compared to controls (p = 0.0093), with a temporal profile showing an early, approximately 5-fold increase on days 1-3 followed by a delayed, >10-fold increase on days 4-6 versus control. α-Synuclein levels were higher in patients treated with normothermia versus hypothermia (p = 0.0033), in patients aged <4 years versus ≥4 years (p < 0.0001), in females versus males (p = 0.0007), in nonaccidental TBI versus accidental TBI victims (p = 0.0003), and in patients with global versus focal injury on computed tomography of the brain (p = 0.046). Comparisons of CSF α-synuclein levels with initial GCS and GOS scores were not statistically significant. Further studies are needed to evaluate the conformational status of α-synuclein in CSF, and whether TH affects α-synuclein aggregation. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]