A thrombospondin-dependent pathway for a protective ER stress response.

Thrombospondin (Thbs) proteins are induced in sites of tissue damage or active remodeling. The endoplasmic reticulum (ER) stress response is also prominently induced with disease where it regulates protein production and resolution of misfolded proteins. Here we describe a function for Thbs as ER-resident effectors of an adaptive ER stress response. Thbs4 cardiac-specific transgenic mice were protected from myocardial injury, whereas Thbs4(-/-) mice were sensitized to cardiac maladaptation. Thbs induction produced a unique profile of adaptive ER stress response factors and expansion of the ER and downstream vesicles. Thbs bind the ER lumenal domain of activating transcription factor 6α (Atf6α) to promote its nuclear shuttling. Thbs4(-/-) mice showed blunted activation of Atf6α and other ER stress-response factors with injury, and Thbs4-mediated protection was lost upon Atf6α deletion. Hence, Thbs can function inside the cell during disease remodeling to augment ER function and protect through a mechanism involving regulation of Atf6α.

Fast skeletal myosin-binding protein-C regulates fast skeletal muscle contraction.

Fast skeletal myosin-binding protein-C (fMyBP-C) is one of three MyBP-C paralogs and is predominantly expressed in fast skeletal muscle. Mutations in the gene that encodes fMyBP-C, MYBPC2, are associated with distal arthrogryposis, while loss of fMyBP-C protein is associated with diseased muscle. However, the functional and structural roles of fMyBP-C in skeletal muscle remain unclear. To address this gap, we generated a homozygous fMyBP-C knockout mouse (C2-/-) and characterized it both in vivo and in vitro compared to wild-type mice. Ablation of fMyBP-C was benign in terms of muscle weight, fiber type, cross-sectional area, and sarcomere ultrastructure. However, grip strength and plantar flexor muscle strength were significantly decreased in C2-/- mice. Peak isometric tetanic force and isotonic speed of contraction were significantly reduced in isolated extensor digitorum longus (EDL) from C2-/- mice. Small-angle X-ray diffraction of C2-/- EDL muscle showed significantly increased equatorial intensity ratio during contraction, indicating a greater shift of myosin heads toward actin, while MLL4 layer line intensity was decreased at rest, indicating less ordered myosin heads. Interfilament lattice spacing increased significantly in C2-/- EDL muscle. Consistent with these findings, we observed a significant reduction of steady-state isometric force during Ca2+-activation, decreased myofilament calcium sensitivity, and sinusoidal stiffness in skinned EDL muscle fibers from C2-/- mice. Finally, C2-/- muscles displayed disruption of inflammatory and regenerative pathways, along with increased muscle damage upon mechanical overload. Together, our data suggest that fMyBP-C is essential for maximal speed and force of contraction, sarcomere integrity, and calcium sensitivity in fast-twitch muscle.

Bereaved Parents: Insights for the Antenatal Consultation.

OBJECTIVE: The study aimed to explore experiences of extremely preterm infant loss in the delivery room and perspectives about antenatal consultation. STUDY DESIGN: Bereaved participants were interviewed, following a semi-structured protocol. Personal narratives were analyzed with a mixed-methods approach. RESULTS: In total, 13 participants, reflecting on 17 pregnancies, shared positive, healing and negative, harmful interactions with clinicians and institutions: feeling cared for or abandoned, doubted or believed, being treated rigidly or flexibly, and feeling that infant's life was valued or not. Participants stressed their need for personalized information, individualized approaches, and affective support. Their decision processes varied; some wanted different things for themselves than what they recommended for others. These interactions shaped their immediate experiences, long-term well-being, healing, and regrets. All had successful subsequent pregnancies; few returned to institutions where they felt poorly treated. CONCLUSION: Antenatal consultations can be strengthened by personalizing them, within a strong caregiver relationship and supportive institutional practices. KEY POINTS: · Personalized antenatal consultations should strive to balance cognitive and affective needs.. · Including perspectives from bereaved parents can strengthen antenatal consultations.. · Trusting provider-parent partnerships are pivotal for risk communication..

Amino terminus of cardiac myosin binding protein-C regulates cardiac contractility.

Phosphorylation of cardiac myosin binding protein-C (cMyBP-C) regulates cardiac contraction through modulation of actomyosin interactions mediated by the protein's amino terminal (N')-region (C0-C2 domains, 358 amino acids). On the other hand, dephosphorylation of cMyBP-C during myocardial injury results in cleavage of the 271 amino acid C0-C1f region and subsequent contractile dysfunction. Yet, our current understanding of amino terminus region of cMyBP-C in the context of regulating thin and thick filament interactions is limited. A novel cardiac-specific transgenic mouse model expressing cMyBP-C, but lacking its C0-C1f region (cMyBP-C∆C0-C1f), displayed dilated cardiomyopathy, underscoring the importance of the N'-region in cMyBP-C. Further exploring the molecular basis for this cardiomyopathy, in vitro studies revealed increased interfilament lattice spacing and rate of tension redevelopment, as well as faster actin-filament sliding velocity within the C-zone of the transgenic sarcomere. Moreover, phosphorylation of the unablated phosphoregulatory sites was increased, likely contributing to normal sarcomere morphology and myoarchitecture. These results led us to hypothesize that restoration of the N'-region of cMyBP-C would return actomyosin interaction to its steady state. Accordingly, we administered recombinant C0-C2 (rC0-C2) to permeabilized cardiomyocytes from transgenic, cMyBP-C null, and human heart failure biopsies, and we found that normal regulation of actomyosin interaction and contractility was restored. Overall, these data provide a unique picture of selective perturbations of the cardiac sarcomere that either lead to injury or adaptation to injury in the myocardium.

Ablation of the calpain-targeted site in cardiac myosin binding protein-C is cardioprotective during ischemia-reperfusion injury.

Cardiac myosin binding protein-C (cMyBP-C) phosphorylation is essential for normal heart function and protects the heart from ischemia-reperfusion (I/R) injury. It is known that protein kinase-A (PKA)-mediated phosphorylation of cMyBP-C prevents I/R-dependent proteolysis, whereas dephosphorylation of cMyBP-C at PKA sites correlates with its degradation. While sites on cMyBP-C associated with phosphorylation and proteolysis co-localize, the mechanisms that link cMyBP-C phosphorylation and proteolysis during cardioprotection are not well understood. Therefore, we aimed to determine if abrogation of cMyBP-C proteolysis in association with calpain, a calcium-activated protease, confers cardioprotection during I/R injury. Calpain is activated in both human ischemic heart samples and ischemic mouse myocardium where cMyBP-C is dephosphorylated and undergoes proteolysis. Moreover, cMyBP-C is a substrate for calpain proteolysis and cleaved by calpain at residues 272-TSLAGAGRR-280, a domain termed as the calpain-target site (CTS). Cardiac-specific transgenic (Tg) mice in which the CTS motif was ablated were bred into a cMyBP-C null background. These Tg mice were conclusively shown to possess a normal basal structure and function by analysis of histology, electron microscopy, immunofluorescence microscopy, Q-space MRI of tissue architecture, echocardiography, and hemodynamics. However, the genetic ablation of the CTS motif conferred resistance to calpain-mediated proteolysis of cMyBP-C. Following I/R injury, the loss of the CTS reduced infarct size compared to non-transgenic controls. Collectively, these findings demonstrate the physiological significance of calpain-targeted cMyBP-C proteolysis and provide a rationale for studying inhibition of calpain-mediated proteolysis of cMyBP-C as a therapeutic target for cardioprotection.

Inhibiting Fibronectin Attenuates Fibrosis and Improves Cardiac Function in a Model of Heart Failure.

BACKGROUND: Fibronectin (FN) polymerization is necessary for collagen matrix deposition and is a key contributor to increased abundance of cardiac myofibroblasts (MFs) after cardiac injury. We hypothesized that interfering with FN polymerization or its genetic ablation in fibroblasts would attenuate MF and fibrosis and improve cardiac function after ischemia/reperfusion (I/R) injury. METHODS: Mouse and human MFs were used to assess the impact of the FN polymerization inhibitor (pUR4) in attenuating pathological cellular features such as proliferation, migration, extracellular matrix deposition, and associated mechanisms. To evaluate the therapeutic potential of inhibiting FN polymerization in vivo, wild-type mice received daily intraperitoneal injections of either pUR4 or control peptide (III-11C) immediately after cardiac surgery for 7 consecutive days. Mice were analyzed 7 days after I/R to assess MF markers and inflammatory cell infiltration or 4 weeks after I/R to evaluate long-term effects of FN inhibition on cardiac function and fibrosis. Furthermore, inducible, fibroblast-restricted, FN gene-ablated (Tcf21MerCreMer; Fnflox) mice were used to evaluate cell specificity of FN expression and polymerization in the heart. RESULTS: pUR4 administration on activated MFs reduced FN and collagen deposition into the extracellular matrix and attenuated cell proliferation, likely mediated through decreased c-myc signaling. pUR4 also ameliorated fibroblast migration accompanied by increased ß1 integrin internalization and reduced levels of phosphorylated focal adhesion kinase protein. In vivo, daily administration of pUR4 for 7 days after I/R significantly reduced MF markers and neutrophil infiltration. This treatment regimen also significantly attenuated myocardial dysfunction, pathological cardiac remodeling, and fibrosis up to 4 weeks after I/R. Last, inducible ablation of FN in fibroblasts after I/R resulted in significant functional cardioprotection with reduced hypertrophy and fibrosis. The addition of pUR4 to the FN-ablated mice did not confer further cardioprotection, suggesting that the salutary effects of inhibiting FN polymerization may be mediated largely through effects on FN secreted from the cardiac fibroblast lineage. CONCLUSIONS: Inhibiting FN polymerization or cardiac fibroblast gene expression attenuates pathological properties of MFs in vitro and ameliorates adverse cardiac remodeling and fibrosis in an in vivo model of heart failure. Interfering with FN polymerization may be a new therapeutic strategy for treating cardiac fibrosis and heart failure.

Sickle cell anemia mice develop a unique cardiomyopathy with restrictive physiology.

Cardiopulmonary complications are the leading cause of mortality in sickle cell anemia (SCA). Elevated tricuspid regurgitant jet velocity, pulmonary hypertension, diastolic, and autonomic dysfunction have all been described, but a unifying pathophysiology and mechanism explaining the poor prognosis and propensity to sudden death has been elusive. Herein, SCA mice underwent a longitudinal comprehensive cardiac analysis, combining state-of-the-art cardiac imaging with electrocardiography, histopathology, and molecular analysis to determine the basis of cardiac dysfunction. We show that in SCA mice, anemia-induced hyperdynamic physiology was gradually superimposed with restrictive physiology, characterized by progressive left atrial enlargement and diastolic dysfunction with preserved systolic function. This phenomenon was absent in WT mice with experimentally induced chronic anemia of similar degree and duration. Restrictive physiology was associated with microscopic cardiomyocyte loss and secondary fibrosis detectable as increased extracellular volume by cardiac-MRI. Ultrastructural mitochondrial changes were consistent with severe chronic hypoxia/ischemia and sarcomere diastolic-length was shortened. Transcriptome analysis revealed up-regulation of genes involving angiogenesis, extracellular-matrix, circadian-rhythm, oxidative stress, and hypoxia, whereas ion-channel transport and cardiac conduction were down-regulated. Indeed, progressive corrected QT prolongation, arrhythmias, and ischemic changes were noted in SCA mice before sudden death. Sudden cardiac death is common in humans with restrictive cardiomyopathies and long QT syndromes. Our findings may thus provide a unifying cardiac pathophysiology that explains the reported cardiac abnormalities and sudden death seen in humans with SCA.

Autonomic dysfunction following traumatic brain injury: translational insights.

Although there is a substantial amount of research on the neurological consequences of traumatic brain injury (TBI), there is a knowledge gap regarding the relationship between TBI and the pathophysiology of organ system dysfunction and autonomic dysregulation. In particular, the mechanisms or incidences of renal or cardiac complications after TBI are mostly unknown. Autonomic dysfunction following TBI exacerbates secondary injury and may contribute to nonneurologial complications that prolong hospital length of stay. Gaining insights into the mechanisms of autonomic dysfunction can guide advancements in monitoring and treatment paradigms to improve acute survival and long-term prognosis of TBI patients. In this paper, the authors will review the literature on autonomic dysfunction after TBI and possible mechanisms of paroxysmal sympathetic hyperactivity. Specifically, they will discuss the link among the brain, heart, and kidneys and review data to direct future research on and interventions for TBI-induced autonomic dysfunction.

You Can't Take Your Baby Home Yet: A Longitudinal Study of Psychological Symptoms in Mothers of Infants Hospitalized in the NICU.

Evidence suggests that mothers of infants hospitalized in the Neonatal Intensive Care Unit (NICU) experience elevated rates of psychological symptoms. However, previous studies of this population have been mainly cross-sectional and have focused on very preterm infants. Although moderate- to late-preterm infants generally thrive, the possible psychological toll on their mothers has not yet been sufficiently examined. In the current study, we used a longitudinal design to investigate whether mothers of moderate- to late-preterm infants experience elevated rates of psychological symptoms during the infant's hospitalization in the NICU and 6 months later. Results indicated that these mothers did show elevated depression, anxiety, and PTSD symptoms, and that symptom levels were similar in mothers of moderate- versus late-preterm infants. Mothers of moderate- to late-preterm infants hospitalized in the NICU appeared to experience these symptoms steadily over a 6-month period after giving birth. These findings suggest a need for greater support for these mothers while in the NICU.

Tranilast Blunts the Hypertrophic and Fibrotic Response to Increased Afterload Independent of Cardiomyocyte Transient Receptor Potential Vanilloid 2 Channels.

Tranilast is clinically indicated for the treatment of allergic disorders and is also a nonselective blocker of the transient receptor potential vanilloid 2 (TRPV2) channel. Previous studies have found that it has protective effects in various animal models of cardiac disease. Our laboratory has found that genetic deletion of TRPV2 results in a blunted hypertrophic response to increased afterload; thus, this study tested the hypothesis that tranilast through cardiomyocyte TRPV2 blockade can inhibit the hypertrophic response to pressure overload in vivo through transverse aortic constriction and ex vivo through isolated myocyte studies. The in vivo studies demonstrated that tranilast blunted the fibrotic response to increased afterload and, to a lesser extent, the hypertrophic response. After 4 weeks, this blunting was associated with improved cardiac function, although at 8 weeks, the cardiac function deteriorated similarly to the control group. Finally, the in vitro studies demonstrated that tranilast was not inhibiting these responses at the cardiomyocyte level. In conclusion, we demonstrated that tranilast blunting of the fibrotic and hypertrophic response occurs independently of cardiac TRPV2 channels and may be cardioprotective in the short term but not after prolonged administration.

Constructing a Culturally Informed Spanish Decision-Aid to Counsel Latino Parents Facing Imminent Extreme Premature Delivery.

Objective How Latino parents perceive and understand antenatal counseling for extreme prematurity, < 26 weeks of gestational age (GA), is not clear. We aim to characterize Latino parental perceptions of antenatal counseling in order to construct and validate a Spanish decision-aid (SDA) to improve parental knowledge of prematurity after antenatal consults. Methods This is a three-phased, prospective, multicenter study. First, interviews of 22 Latino parents with a history of birth < 26 weeks GA were conducted. Thematic analysis identified themes valued during antenatal counseling for decisions regarding neonatal resuscitation. Next, we incorporated these themes into the SDA. Finally, improvement in knowledge of prematurity in two Spanish-speaking groups, 'experienced' parents with a history of extremely premature birth and 'naïve' adult Latino volunteers, was measured using a multiple choice test before and after simulated counseling with the SDA. Result Twenty-two interviews generated seven unique themes. An SDA was constructed that preserved six themes paralleled by those found in a previously studied English population, and addressed a novel theme of "intercultural linguistic barriers" unique to our population. Knowledge scores rose in "naive" volunteers, 41 ± 12% to 71 ± 15% (P < 0.001), after simulated counseling with the SDA. 'Experienced' parents had a ceiling effect in knowledge scores, 62 ± 9% to 65 ± 11% (P = 0.22). The SDA was well received by participants. Conclusions for Practice Interviews of Latino parents with a history of premature birth generated similar themes to English-speaking parents, with intercultural linguistic barriers as a novel theme. An SDA for Latino parents facing extremely premature birth may improve comprehension of antenatal counseling.

Provider Perceptions of Bubble Continuous Positive Airway Pressure and Barriers to Implementation in a Level III Neonatal Unit in South India.

BACKGROUND: Bubble continuous positive airway pressure (bCPAP) is a simple, safe, and cost-effective strategy to provide respiratory support to newborns with respiratory distress syndrome in resource-limited settings. PURPOSE: To understand whether implementation of bCPAP, relative to other modes of respiratory support in the care of newborns with respiratory distress syndrome, increases positive attitudes about its potential for consistent and widespread use among providers in neonatal intensive care units (NICUs) of lower middle-income countries. METHODS: Semistructured qualitative interviews with 14 healthcare providers, including 5 neonatal nurses, 2 respiratory therapists, 5 postgraduate trainees in pediatrics, and 2 attending physicians, were conducted at a level III NICU in south India where bCPAP had been in consistent use for 6 years. Interviews were transcribed and then coded and categorized using NVivo 10 Software (QSR International, Victoria, Australia). FINDINGS: Categories that emerged from our data include (1) perceived indications, (2) learning curve, (3) perceived costs, (4) perceived shortages, and (5) barriers to use. Providers believed that bCPAP was easy to learn and that it helped empower neonatal nurses in decision-making process. Participants provided a nuanced perspective of cost-benefit associated with bCPAP and that it helped make optimal use of limited resources. Participants identified several barriers to the implementation of bCPAP. IMPLICATIONS FOR PRACTICE: Providers of a level III NICU in a lower- to middle-income country viewed the use of bCPAP favorably. Addressing context-specific barriers will be important for the successful widespread implementation of bCPAP. IMPLICATIONS FOR RESEARCH: Further research will need to focus on whether bCPAP can be safely implemented at level II NICUs.Video Abstract Available at https://journals.lww.com/advancesinneonatalcare/Pages/videogallery.aspx.

Overexpression of miR-223 Tips the Balance of Pro- and Anti-hypertrophic Signaling Cascades toward Physiologic Cardiac Hypertrophy.

MicroRNAs (miRNAs) have been extensively examined in pathological cardiac hypertrophy. However, few studies focused on profiling the miRNA alterations in physiological hypertrophic hearts. In this study we generated a transgenic mouse model with cardiac-specific overexpression of miR-223. Our results showed that elevation of miR-223 caused physiological cardiac hypertrophy with enhanced cardiac function but no fibrosis. Using the next generation RNA sequencing, we observed that most of dys-regulated genes (e.g. Atf3/5, Egr1/3, Sfrp2, Itgb1, Ndrg4, Akip1, Postn, Rxfp1, and Egln3) in miR-223-transgenic hearts were associated with cell growth, but they were not directly targeted by miR-223. Interestingly, these dys-regulated genes are known to regulate the Akt signaling pathway. We further identified that miR-223 directly interacted with 3'-UTRs of FBXW7 and Acvr2a, two negative regulators of the Akt signaling. However, we also validated that miR-223 directly inhibited the expression of IGF-1R and ß1-integrin, two positive regulators of the Akt signaling. Lastly, Western blotting did reveal that Akt was activated in miR-223-overexpressing hearts. Adenovirus-mediated overexpression of miR-223 in neonatal rat cardiomyocytes induced cell hypertrophy, which was blocked by the addition of MK2206, a specific inhibitor of Akt Taken together, these data represent the first piece of work showing that miR-223 tips the balance of promotion and inactivation of Akt signaling cascades toward activation of Akt, a key regulator of physiological cardiac hypertrophy. Thus, our study suggests that the ultimate phenotype outcome of a miRNA may be decided by the secondary net effects of the whole target network rather than by several primary direct targets in an organ/tissue.

In vivo definition of cardiac myosin-binding protein C's critical interactions with myosin.

Cardiac myosin-binding protein C (cMyBP-C) is an integral part of the sarcomeric machinery in cardiac muscle that enables normal function. cMyBP-C regulates normal cardiac contraction by functioning as a brake through interactions with the sarcomere's thick, thin, and titin filaments. cMyBP-C's precise effects as it binds to the different filament systems remain obscure, particularly as it impacts on the myosin heavy chain's head domain, contained within the subfragment 2 (S2) region. This portion of the myosin heavy chain also contains the ATPase activity critical for myosin's function. Mutations in myosin's head, as well as in cMyBP-C, are a frequent cause of familial hypertrophic cardiomyopathy (FHC). We generated transgenic lines in which endogenous cMyBP-C was replaced by protein lacking the residues necessary for binding to S2 (cMyBP-C(S2-)). We found, surprisingly, that cMyBP-C lacking the S2 binding site is incorporated normally into the sarcomere, although systolic function is compromised. We show for the first time the acute and chronic in vivo consequences of ablating a filament-specific interaction of cMyBP-C. This work probes the functional consequences, in the whole animal, of modifying a critical structure-function relationship, the protein's ability to bind to a region of the critical enzyme responsible for muscle contraction, the subfragment 2 domain of the myosin heavy chain. We show that the binding is not critical for the protein's correct insertion into the sarcomere's architecture, but is essential for long-term, normal function in the physiological context of the heart.

Is urinary neutrophil gelatinase-associated lipocalin able to predict acute kidney injury episodes in very low birth weight infants in clinical settings?

BACKGROUND: We evaluated the potential utility of elevated urinary neutrophil gelatinase-associated lipocalin (UNGAL) concentration as a screening test for early identification of acute kidney injury (AKI) in very low birth weight (VLBW) newborns. METHODS: Urine for UNGAL analysis was collected prospectively daily until 32 wk postmenstrual age in 91 VLBW newborns, yielding 2,899 specimens. UNGAL values > 50 ng/ml were considered elevated. AKI was defined as two or more consecutive elevations in s[Cr] above the 95th percentile adjusted for gestational age and chronological age within a 48 h period. We compared UNGAL values taken during the 5 d prior to AKI onset (pre-AKI) to values taken during non-AKI days. RESULTS: Overall, 15 episodes of AKI were identified in 13 infants. UNGAL was available in 44 pre-AKI days and 969 non-AKI days. UNGAL > 50 ng/ml occurred more often in pre-AKI days than in non-AKI days (risk ratio 3.48 (1.89, 6.40)). Positive and negative likelihood ratios were 1.92 (1.52, 2.41) and 0.52 (0.34, 0.78), respectively. CONCLUSION: Although UNGAL elevation > 50 ng/ml discriminates between pre-AKI and non-AKI days, high false positive and false negative rates limit utility as a screening test in VLBW newborns.

Urinary neutrophil gelatinase-associated lipocalin: potential biomarker for late-onset sepsis.

BACKGROUND: To assess the ability of urinary neutrophil gelatinase-associated lipocalin (UNGAL) to discriminate between culture-positive vs. culture-negative late-onset sepsis evaluations. METHODS: This is a prospective observational study of 136 neonates who underwent ≥1 sepsis evaluation at >72 h of age. Urine was obtained at the time of sepsis evaluation to measure UNGAL concentration. Using generalized estimating equations controlling for gender, gestational and postnatal age, acute kidney injury, and within-patient correlations, pair-wise contrasts between mean log UNGAL concentrations of infants with negative sepsis evaluations vs. culture-positive sepsis and presumed sepsis were assessed. Discrimination characteristics at several UNGAL cutoff concentrations were assessed using receiver-operating characteristic curves. RESULTS: The predicted mean log UNGAL values of culture-positive sepsis and presumed sepsis vs. negative sepsis evaluations differed significantly (P < 0.001 and P = 0.02, respectively). At a cutoff ≥ 50 ng/ml, UNGAL discriminated between culture-positive sepsis and culture-negative sepsis evaluations with sensitivity = 86%, specificity = 56%, positive predictive value = 41%, negative predictive value = 92%, and number needed to treat = 3. CONCLUSION: UNGAL is a noninvasive biomarker with high negative predictive value at the time of late-onset sepsis evaluation in neonates and could be a useful adjunct to traditional components of sepsis evaluations.

Serum creatinine concentration in very-low-birth-weight infants from birth to 34-36 wk postmenstrual age.

BACKGROUND: Serum creatinine (s[Cr]) reference ranges for very-low-birth-weight (VLBW) infants must account for physiologic changes in the first months of life. METHODS: We retrospectively identified a sample of 218 appropriate-for-gestational age (GA) VLBW infants without risk factors for renal impairment, and classified into one of three GA groups: 25-27, 28-29, and 30-33 wk. We observed three phases of s[Cr] change (initial, decline, and equilibrium), whose characteristics varied by GA group. We used mixed-effects regression models to estimate mean and upper 95th prediction interval of s[Cr] for each GA group from birth to 34-36 wk post menstrual age (PMA). RESULTS: In phase I, s[Cr] increased after birth, then returned slowly to baseline. The duration of phase I and the magnitude of s[Cr] rise decreased with increasing GA. In phase II, s[Cr] declined abruptly at a rate that increased with GA. A gradual transition to phase III, a steady-state equilibrium with similar s[Cr] among GA groups, began at approximately 34-36 wk PMA. We constructed GA group-specific nomograms depicting s[Cr] behaviour across the three phases. CONCLUSION: The reference ranges derived from a sample of infants without risk factors for renal impairment provide a context for quantitative interpretation of s[Cr] trends in VLBW infants.

Unrestrained p38 MAPK activation in Dusp1/4 double-null mice induces cardiomyopathy.

RATIONALE: Mitogen-activated protein kinases (MAPKs) are activated in the heart by disease-inducing and stress-inducing stimuli, where they participate in hypertrophy, remodeling, contractility, and heart failure. A family of dual-specificity phosphatases (DUSPs) directly inactivates each of the MAPK terminal effectors, potentially serving a cardioprotective role. OBJECTIVE: To determine the role of DUSP1 and DUSP4 in regulating p38 MAPK function in the heart and the effect on disease. METHODS AND RESULTS: Here, we generated mice and mouse embryonic fibroblasts lacking both Dusp1 and Dusp4 genes. Although single nulls showed no molecular effects, combined disruption of Dusp1/4 promoted unrestrained p38 MAPK activity in both mouse embryonic fibroblasts and the heart, with no change in the phosphorylation of c-Jun N-terminal kinases or extracellular signal-regulated kinases at baseline or with stress stimulation. Single disruption of either Dusp1 or Dusp4 did not result in cardiac pathology, although Dusp1/4 double-null mice exhibited cardiomyopathy and increased mortality with aging. Pharmacological inhibition of p38 MAPK with SB731445 ameliorated cardiomyopathy in Dusp1/4 double-null mice, indicating that DUSP1/4 function primarily through p38 MAPK in affecting disease. At the cellular level, unrestrained p38 MAPK activity diminished cardiac contractility and Ca2+ handling, which was acutely reversed with a p38 inhibitory compound. Poor function in Dusp1/4 double-null mice also was partially rescued by phospholamban deletion. CONCLUSIONS: Our data demonstrate that Dusp1 and Dusp4 are cardioprotective genes that play a critical role in the heart by dampening p38 MAPK signaling that would otherwise reduce contractility and induce cardiomyopathy.