Comprehensive Multi-omics Analysis Reveals Mitochondrial Stress as a Central Biological Hub for Spaceflight Impact.

Spaceflight is known to impose changes on human physiology with unknown molecular etiologies. To reveal these causes, we used a multi-omics, systems biology analytical approach using biomedical profiles from fifty-nine astronauts and data from NASA's GeneLab derived from hundreds of samples flown in space to determine transcriptomic, proteomic, metabolomic, and epigenetic responses to spaceflight. Overall pathway analyses on the multi-omics datasets showed significant enrichment for mitochondrial processes, as well as innate immunity, chronic inflammation, cell cycle, circadian rhythm, and olfactory functions. Importantly, NASA's Twin Study provided a platform to confirm several of our principal findings. Evidence of altered mitochondrial function and DNA damage was also found in the urine and blood metabolic data compiled from the astronaut cohort and NASA Twin Study data, indicating mitochondrial stress as a consistent phenotype of spaceflight.

CRISPR screen for protein inclusion formation uncovers a role for SRRD in the regulation of intermediate filament dynamics and aggresome assembly.

The presence of large protein inclusions is a hallmark of neurodegeneration, and yet the precise molecular factors that contribute to their formation remain poorly understood. Screens using aggregation-prone proteins have commonly relied on downstream toxicity as a readout rather than the direct formation of aggregates. Here, we combined a genome-wide CRISPR knockout screen with Pulse Shape Analysis, a FACS-based method for inclusion detection, to identify direct modifiers of TDP-43 aggregation in human cells. Our screen revealed both canonical and novel proteostasis genes, and unearthed SRRD, a poorly characterized protein, as a top regulator of protein inclusion formation. APEX biotin labeling reveals that SRRD resides in proximity to proteins that are involved in the formation and breakage of disulfide bonds and to intermediate filaments, suggesting a role in regulation of the spatial dynamics of the intermediate filament network. Indeed, loss of SRRD results in aberrant intermediate filament fibrils and the impaired formation of aggresomes, including blunted vimentin cage structure, during proteotoxic stress. Interestingly, SRRD also localizes to aggresomes and unfolded proteins, and rescues proteotoxicity in yeast whereby its N-terminal low complexity domain is sufficient to induce this affect. Altogether this suggests an unanticipated and broad role for SRRD in cytoskeletal organization and cellular proteostasis.

Neutral sphingomyelinase blockade enhances hematopoietic stem cell fitness through an integrated stress response.

Hematopoietic stem and progenitor cell (HSPC) transplantation serves as a curative therapy for many benign and malignant hematopoietic disorders and as a platform for gene therapy. However, growing needs for ex vivo manipulation of HSPC-graft products are limited by barriers in maintaining critical self-renewal and quiescence properties. The role of sphingolipid metabolism in safeguarding these essential cellular properties has been recently recognized, but not yet widely explored. Here, we demonstrate that pharmacologic and genetic inhibition of neutral sphingomyelinase 2 (nSMase-2) leads to sustained improvements in long-term competitive transplantation efficiency after ex vivo culture. Mechanistically, nSMase-2 blockade activates a canonical integrated stress response (ISR) and promotes metabolic quiescence in human and murine HSPCs. These adaptations result in part from disruption in sphingolipid metabolism that impairs the release of nSMase-2-dependent extracellular vesicles (EVs). The aggregate findings link EV trafficking and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, transient nSMase-2 inhibition enables ex vivo graft manipulation with enhanced HSPC potency.

The Ubiquitin Ligase Itch Skews Light Zone Selection in Germinal Centers.

Ig diversification occurs in peripheral lymphoid organs after establishment of central tolerance during B cell development. In germinal centers (GCs), somatic hypermutation of Ig genes occurs in dark zones, followed by selection of mutated clones in light zones (LZs). This generates high-affinity Ig receptors to pathogens but can also produce autoreactive Ig receptors, which are removed by selection mechanisms that are incompletely understood. The ubiquitin ligase Itch prevents the emergence of autoimmune disease and autoantibodies in humans and mice, and patients lacking Itch develop potentially fatal autoimmune diseases; yet, how Itch regulates GC B cells is not well understood. By studying Itch-deficient mice, we have recently shown that Itch directly limits the magnitude of GC responses. Proteomic profiling of GC B cells uncovered that Itch-deficient cells exhibit high mTORC1 and Myc activity, hallmarks of positive selection. Bone marrow chimera and adoptive transfer experiments revealed that B cell Itch restricts noncycling LZ cells. These results support, to our knowledge, a novel role for Itch in skewing selection of GC B cells to restrict LZ accumulation and shape GC-derived humoral immunity. Determining how B cells integrate cues within GCs to navigate through LZs and dark zones will aid in understanding how autoreactive clones emerge from GCs in people with autoimmune disease.

Unveiling the human nitroproteome: Protein tyrosine nitration in cell signaling and cancer.

Covalent amino acid modification significantly expands protein functional capability in regulating biological processes. Tyrosine residues can undergo phosphorylation, sulfation, adenylation, halogenation, and nitration. These posttranslational modifications (PTMs) result from the actions of specific enzymes: tyrosine kinases, tyrosyl-protein sulfotransferase(s), adenylate transferase(s), oxidoreductases, peroxidases, and metal-heme containing proteins. Whereas phosphorylation, sulfation, and adenylation modify the hydroxyl group of tyrosine, tyrosine halogenation and nitration target the adjacent carbon residues. Because aberrant tyrosine nitration has been associated with human disorders and with animal models of disease, we have created an updated and curated database of 908 human nitrated proteins. We have also analyzed this new resource to provide insight into the role of tyrosine nitration in cancer biology, an area that has not previously been considered in detail. Unexpectedly, we have found that 879 of the 1971 known sites of tyrosine nitration are also sites of phosphorylation suggesting an extensive role for nitration in cell signaling. Overall, the review offers several forward-looking opportunities for future research and new perspectives for understanding the role of tyrosine nitration in cancer biology.

Stratification of neurogenic bladder risk in spina bifida using the urinary peptidome.

Neurogenic bladder poses a major morbidity in children with spina bifida (SB), and videourodynamic studies (VUDS) are used to stratify this risk. This small-scale pilot study utilized current mass-spectrometry-based proteomic approaches to identify peptides or proteins in urine that may differentiate children at high risk of developing renal complications from a neurogenic bladder. Twenty-two urine samples of which nine had high bladder pressure storage that put the upper urinary tract at risk, while 13 with a lower risk for renal compromise were analyzed. More than 1,900 peptides across all 22 samples were quantified, and 115 peptides differed significantly (P < 0.05) between the two groups. Using machine learning approaches five peptides that showed the greatest differences between these two clinical categories were used to build a classifier. We tested this classifier by blind analysis of an additional six urine samples and showed that it correctly assigned the unknown samples in their proper risk category. These promising results indicate that a urinary screening test based on peptides could be performed on a regular basis to stratify the neurogenic bladder into low or high-risk categories. Expanding this work to larger cohorts as well as across a broad spectrum of urodynamics outcomes may provide a useful diagnostic test for neurogenic bladder.NEW & NOTEWORTHY This approach could help risk stratify the neurogenic bladder in patients with spina bifida and could allow us to safely defer on up to 1/3 of urodynamic studies. These pilot data justify a larger trial before this approach becomes a clinical tool.

The E3 ubiquitin ligase Cul4b promotes CD4+ T cell expansion by aiding the repair of damaged DNA.

The capacity for T cells to become activated and clonally expand during pathogen invasion is pivotal for protective immunity. Our understanding of how T cell receptor (TCR) signaling prepares cells for this rapid expansion remains limited. Here we provide evidence that the E3 ubiquitin ligase Cullin-4b (Cul4b) regulates this process. The abundance of total and neddylated Cul4b increased following TCR stimulation. Disruption of Cul4b resulted in impaired proliferation and survival of activated T cells. Additionally, Cul4b-deficient CD4+ T cells accumulated DNA damage. In T cells, Cul4b preferentially associated with the substrate receptor DCAF1, and Cul4b and DCAF1 were found to interact with proteins that promote the sensing or repair of damaged DNA. While Cul4b-deficient CD4+ T cells showed evidence of DNA damage sensing, downstream phosphorylation of SMC1A did not occur. These findings reveal an essential role for Cul4b in promoting the repair of damaged DNA to allow survival and expansion of activated T cells.

Proteomics identifies novel biomarkers of synovial joint disease in a canine model of mucopolysaccharidosis I.

Mucopolysaccharidosis I is a lysosomal storage disorder characterized by deficient alpha-L-iduronidase activity, leading to abnormal accumulation of glycosaminoglycans in cells and tissues. Synovial joint disease is prevalent and significantly reduces patient quality of life. There is a critical need for improved understanding of joint disease pathophysiology in MPS I, including specific biomarkers to predict and monitor joint disease progression, and response to treatment. The objective of this study was to leverage the naturally-occurring MPS I canine model and undertake an unbiased proteomic screen to identify systemic biomarkers predictive of local joint disease in MPS I. Synovial fluid and serum samples were collected from MPS I and healthy dogs at 12 months-of-age, and protein abundance characterized using liquid chromatography tandem mass spectrometry. Stifle joints were evaluated postmortem using magnetic resonance imaging (MRI) and histology. Proteomics identified 40 proteins for which abundance was significantly correlated between serum and synovial fluid, including markers of inflammatory joint disease and lysosomal dysfunction. Elevated expression of three biomarker candidates, matrix metalloproteinase 19, inter-alpha-trypsin inhibitor heavy-chain 3 and alpha-1-microglobulin, was confirmed in MPS I cartilage, and serum abundance of these molecules was found to correlate with MRI and histological degenerative grades. The candidate biomarkers identified have the potential to improve patient care by facilitating minimally-invasive, specific assessment of joint disease progression and response to therapeutic intervention.

An interdomain helix in IRE1α mediates the conformational change required for the sensor's activation.

The unfolded protein response plays an evolutionarily conserved role in homeostasis, and its dysregulation often leads to human disease, including diabetes and cancer. IRE1α is a major transducer that conveys endoplasmic reticulum stress via biochemical signals, yet major gaps persist in our understanding of how the detection of stress is converted to one of several molecular outcomes. It is known that, upon sensing unfolded proteins via its endoplasmic reticulum luminal domain, IRE1α dimerizes and then oligomerizes (often visualized as clustering). Once assembled, the kinase domain trans-autophosphorylates a neighboring IRE1α, inducing a conformational change that activates the RNase effector domain. However, the full details of how the signal is transmitted are not known. Here, we describe a previously unrecognized role for helix αK, located between the kinase and RNase domains of IRE1α, in conveying this critical conformational change. Using constructs containing mutations within this interdomain helix, we show that distinct substitutions affect oligomerization, kinase activity, and the RNase activity of IRE1α differentially. Furthermore, using both biochemical and computational methods, we found that different residues at position 827 specify distinct conformations at distal sites of the protein, such as in the RNase domain. Of importance, an RNase-inactive mutant, L827P, can still dimerize with wildtype monomers, but this mutation inactivates the wildtype molecule and renders leukemic cells more susceptible to stress. We surmise that helix αK is a conduit for the activation of IRE1α in response to stress.

Differentiating children with sepsis with and without acute respiratory distress syndrome using proteomics.

Both sepsis and acute respiratory distress syndrome (ARDS) rely on imprecise clinical definitions leading to heterogeneity, which has contributed to negative trials. Because circulating protein/DNA complexes have been implicated in sepsis and ARDS, we aimed to develop a proteomic signature of DNA-bound proteins to discriminate between children with sepsis with and without ARDS. We performed a prospective case-control study in 12 children with sepsis with ARDS matched to 12 children with sepsis without ARDS on age, severity of illness score, and source of infection. We performed co-immunoprecipitation and downstream proteomics in plasma collected ≤ 24 h of intensive care unit admission. Expression profiles were generated, and a random forest classifier was used on differentially expressed proteins to develop a signature which discriminated ARDS. The classifier was tested in six independent blinded samples. Neutrophil and nucleosome proteins were over-represented in ARDS, including two S100A proteins, superoxide dismutase (SOD), and three histones. Random forest produced a 10-protein signature that accurately discriminated between children with sepsis with and without ARDS. This classifier perfectly assigned six independent blinded samples as having ARDS or not. We validated higher expression of the most informative discriminating protein, galectin-3-binding protein, in children with ARDS. Our methodology has applicability to isolation of DNA-bound proteins from plasma. Our results support the premise of a molecular definition of ARDS, and give preliminary insight into why some children with sepsis, but not others, develop ARDS.

Longitudinal Large-Scale Semiquantitative Proteomic Data Stability Across Multiple Instrument Platforms.

With the rapid developments in mass spectrometry (MS)-based proteomics methods, label-free semiquantitative proteomics has become an increasingly popular tool for profiling global protein abundances in an unbiased manner. However, the reproducibility of these data across time and LC-MS platforms is not well characterized. Here, we evaluate the performance of three LC-MS platforms (Orbitrap Elite, Q Exactive HF, and Orbitrap Fusion) in label-free semiquantitative analysis of cell surface proteins over a six-year period. Sucrose gradient ultracentrifugation was used for surfaceome enrichment, following gel separation for in-depth protein identification. With our established workflow, we consistently detected and reproducibly quantified >2300 putative cell surface proteins in a human acute myeloid leukemia (AML) cell line on all three platforms. To our knowledge this is the first study reporting highly reproducible semiquantitative proteomic data collection of biological replicates across multiple years and LC-MS platforms. These data provide experimental justification for semiquantitative proteomic study designs that are executed over multiyear time intervals and on different platforms. Multiyear and multiplatform experimental designs will likely enable larger scale proteomic studies and facilitate longitudinal proteomic studies by investigators lacking access to high throughput MS facilities. Data are available via ProteomeXchange with identifier PXD022721.

Itch attenuates CD4 T-cell proliferation in mice by limiting WBP2 protein stability.

To mount an antipathogen response, CD4 T cells must undergo rapid cell proliferation; however, poorly controlled expansion can result in diseases such as autoimmunity. One important regulator of T-cell activity is the E3 ubiquitin ligase Itch. Itch deficient patients suffer from extensive autoinflammation. Similarly, Itch deficient mice exhibit inflammation characterized by high numbers of activated CD4 T cells. While the role of Itch in limiting CD4 T-cell cytokine production has been extensively studied, it is less clear whether and how Itch regulates proliferation of these cells. We determined that Itch deficient CD4 T cells are hyperproliferative in vitro and in vivo, due to increased S phase entry. Whole cell proteomics analysis of Itch deficient primary mouse CD4 T cells revealed increased abundance of the ß-catenin coactivator WW domain-binding protein 2 (WBP2). Furthermore, Itch deficient cells demonstrate increased WBP2 protein stability, and Itch and WBP2 interact in CD4 T cells. Knockdown of WBP2 in CD4 T cells caused reduced proliferation. Together, our data support that Itch attenuates CD4 T cell proliferation by promoting WBP2 degradation. This study identifies novel roles for Itch and WBP2 in regulating CD4 T cell proliferation, providing insight into how Itch may prevent inflammation.

Plasma Nucleosomes Are Associated With Mortality in Pediatric Acute Respiratory Distress Syndrome.

OBJECTIVES: Circulating nucleosomes and their component histones have been implicated as pathogenic in sepsis and acute respiratory distress syndrome in adults. However, their role in pediatric acute respiratory distress syndrome is unknown. DESIGN: We performed a prospective cohort study in children with acute respiratory distress syndrome, with plasma collection within 24 hours of acute respiratory distress syndrome onset. We associated nucleosome levels with severity of acute respiratory distress syndrome and with nonpulmonary organ failures and tested for association of nucleosomes with PICU mortality and ventilator-free days at 28 days in univariate and multivariable analyses. We also performed proteomics of DNA-bound plasma proteins in a matched case-control study of septic children with and without acute respiratory distress syndrome in order to identify specific histone proteins elevated in acute respiratory distress syndrome. SETTING: Large academic tertiary-care PICU. PATIENTS: Intubated children meeting Berlin criteria for acute respiratory distress syndrome. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We enrolled 333 children with acute respiratory distress syndrome, with 69 nonsurvivors (21%). Plasma nucleosomes were correlated with acute respiratory distress syndrome severity and with the number of nonpulmonary organ failures at acute respiratory distress syndrome onset. Nucleosomes were higher (p < 0.001) in nonsurvivors (0.40 [interquartile range, 0.20-0.71] arbitrary units) relative to survivors (0.10 [interquartile range, 0.04-0.25] arbitrary units). Nucleosomes were associated with PICU mortality in multivariable analysis (adjusted odds ratio 1.84 per 1 sd increase; 95% CI, 1.38-2.45; p < 0.001). Nucleosomes were also associated with a lower probability of being extubated alive by day 28 after multivariable adjustment (adjusted subdistribution hazard ratio, 0.74; 95% CI, 0.63-0.88; p = 0.001). Proteomic analysis demonstrated higher levels of the core nucleosome histones H2A, H2B, H3, and H4 in septic children with acute respiratory distress syndrome, relative to septic children without acute respiratory distress syndrome. CONCLUSIONS: Plasma nucleosomes are associated with acute respiratory distress syndrome severity, nonpulmonary organ failures, and worse outcomes in pediatric acute respiratory distress syndrome.

Urine Proteomics: Evaluation of Different Sample Preparation Workflows for Quantitative, Reproducible, and Improved Depth of Analysis.

The growing field of urinary proteomics shows promise to expand the number of biomarkers for the diagnosis and prognosis of a number of human diseases. With the rapid developments in mass spectrometry methods for proteome quantification, there exists an opportunity for improved sample processing and separation workflows to make important contributions to urine proteomic analyses. Here we evaluate the performance of four sample preparation methods: MStern, PreOmics in-StageTip (iST), suspension-trapping (S-Trap), and conventional urea In-Solution trypsin hydrolysis for nondepleted urine samples. Data-dependent acquisition (DDA) mode on a QExactive HF mass spectrometer was used for single-shot label-free data acquisition. Our results demonstrate a high degree of reproducibility within each workflow. PreOmics iST yields the best digestion efficiency, whereas the S-Trap workflow gives the greatest number of peptide and protein identifications. Using the S-Trap method and starting with ∼0.5 mL, we identify ∼1500 protein groups and ∼17 700 peptides from DDA analysis with a single injection on the mass spectrometer.

Improved surfaceome coverage with a label-free nonaffinity-purified workflow.

The proteins of the cellular plasma membrane (PM) perform important functions relating to homeostasis and intercellular communication. Due to its overall low cellular abundance, amphipathic character, and low membrane-to-cytoplasm ratio, the PM proteome has been challenging to isolate and characterize, and is poorly represented in standard LC-MS/MS analyses. In this study, we employ sucrose gradient ultracentrifugation for the enrichment of the PM proteome, without chemical labeling and affinity purification, together with GeLCMS and use subsequent bioinformatics tools to select proteins associated with the PM/cell surface, herein referred to as the surfaceome. Using this methodology, we identify over 1900 cell surface associated proteins in a human acute myeloid leukemia cell line. These surface proteins comprise almost 50% of all detected cellular proteins, a number that substantially exceeds the depth of coverage in previously published studies describing the leukemia surfaceome.

Ultrafast hydrogen exchange reveals specific structural events during the initial stages of folding of cytochrome c.

Many proteins undergo a sharp decrease in chain dimensions during early stages of folding, prior to the rate-limiting step in folding. However, it remains unclear whether compact states are the result of specific folding events or a general hydrophobic collapse of the poly peptide chain driven by the change in solvent conditions. To address this fundamental question, we extended the temporal resolution of NMR-detected H/D exchange labeling experiments into the microsecond regime by adopting a microfluidics approach. By observing the competition between H/D exchange and folding as a function of labeling pH, coupled with direct measurement of exchange rates in the unfolded state, we were able to monitor hydrogen-bond formation for over 50 individual backbone NH groups within the initial 140 microseconds of folding of horse cytochrome c. Clusters of solvent-shielded amide protons were observed in two α-helical segments in the C-terminal half of the protein, while the N-terminal helix remained largely unstructured, suggesting that proximity in the primary structure is a major factor in promoting helix formation and association at early stages of folding, while the entropically more costly long-range contacts between the N- and C-terminal helices are established only during later stages. Our findings clearly indicate that the initial chain condensation in cytochrome c is driven by specific interactions among a subset of α-helical segments rather than a general hydrophobic collapse.

Sequential CRISPR screening reveals partial NatB inhibition as a strategy to mitigate alpha-synuclein levels in human neurons.

Alpha-synuclein (αSyn) protein levels correlate with the risk and severity of Parkinson's disease and related neurodegenerative diseases. Lowering αSyn is being actively investigated as a therapeutic modality. Here, we systematically map the regulatory network that controls endogenous αSyn using sequential CRISPR-knockout and -interference screens in an αSyn gene (SNCA)-tagged cell line and induced pluripotent stem cell-derived neurons (iNeurons). We uncover αSyn modifiers at multiple regulatory layers, with amino-terminal acetyltransferase B (NatB) enzymes being the most potent endogenous αSyn modifiers in both cell lines. Amino-terminal acetylation protects the cytosolic αSyn from rapid degradation by the proteasome in a Ube2w-dependent manner. Moreover, we show that pharmacological inhibition of methionyl-aminopeptidase 2, a regulator of NatB complex formation, attenuates endogenous αSyn in iNeurons carrying SNCA triplication. Together, our study reveals several gene networks that control endogenous αSyn, identifies mechanisms mediating the degradation of nonacetylated αSyn, and illustrates potential therapeutic pathways for decreasing αSyn levels in synucleinopathies.

An exploration of mechanisms underlying Desemzia incerta colonization resistance to methicillin-resistant Staphylococcus aureus on the skin.

Colonization of human skin and nares by methicillin-resistant Staphylococcus aureus (MRSA) leads to the community spread of MRSA. This spread is exacerbated by the transfer of MRSA between humans and livestock, particularly swine. Here, we capitalized on the shared features between human and porcine skin, including shared MRSA colonization, to study novel bacterial mediators of MRSA colonization resistance. We focused on the poorly studied bacterial species Desemzia incerta, which we found to exert antimicrobial activity through a secreted product and exhibited colonization resistance against MRSA in an in vivo murine skin model. Using parallel genomic and biochemical investigation, we discovered that D. incerta secretes an antimicrobial protein. Sequential protein purification and proteomics analysis identified 24 candidate inhibitory proteins, including a promising peptidoglycan hydrolase candidate. Aided by transcriptional analysis of D. incerta and MRSA cocultures, we found that exposure to D. incerta leads to decreased MRSA biofilm production. These results emphasize the value of exploring microbial communities across a spectrum of hosts, which can lead to novel therapeutic agents as well as an increased understanding of microbial competition.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) causes a significant healthcare burden and can be spread to the human population via livestock transmission. Members of the skin microbiome can prevent MRSA colonization via a poorly understood phenomenon known as colonization resistance. Here, we studied the colonization resistance of S. aureus by bacterial inhibitors previously identified from a porcine skin model. We identify a pig skin commensal, Desemzia incerta, that reduced MRSA colonization in a murine model. We employ a combination of genomic, proteomic, and transcriptomic analyses to explore the mechanisms of inhibition between D. incerta and S. aureus. We identify 24 candidate antimicrobial proteins secreted by D. incerta that could be responsible for its antimicrobial activity. We also find that exposure to D. incerta leads to decreased S. aureus biofilm formation. These findings show that the livestock transmission of MRSA can be exploited to uncover novel mechanisms of MRSA colonization resistance.

Quantitative label-free mass spectrometry reveals content and signaling differences between neonatal and adult platelets.

BACKGROUND: Recent clinical studies have shown that transfusions of adult platelets increase morbidity and mortality in preterm infants. Neonatal platelets are hyporesponsive to agonist stimulation, and emerging evidence suggests developmental differences in platelet immune functions. OBJECTIVES: This study was designed to compare the proteome and phosphoproteome of resting adult and neonatal platelets. METHODS: We isolated resting umbilical cord blood-derived platelets from healthy full-term neonates (n = 8) and resting blood platelets from healthy adults (n = 6) and compared protein and phosphoprotein contents using data-independent acquisition mass spectrometry. RESULTS: We identified 4770 platelet proteins with high confidence across all samples. Adult and neonatal platelets were clustered separately by principal component analysis. Adult platelets were significantly enriched in immunomodulatory proteins, including ß2 microglobulin and CXCL12, whereas neonatal platelets were enriched in ribosomal components and proteins involved in metabolic activities. Adult platelets were enriched in phosphorylated GTPase regulatory enzymes and proteins participating in trafficking, which may help prime them for activation and degranulation. Neonatal platelets were enriched in phosphorylated proteins involved in insulin growth factor signaling. CONCLUSION: Using label-free data-independent acquisition mass spectrometry, our findings expanded the known neonatal platelet proteome and identified important differences in protein content and phosphorylation between neonatal and adult platelets. These developmental differences suggested enhanced immune functions for adult platelets and presence of molecular machinery related to platelet activation. These findings are important to understanding mechanisms underlying key platelet functions as well as the harmful effects of adult platelet transfusions given to preterm infants.

Effect of dimethyl fumarate on mitochondrial metabolism in a pediatric porcine model of asphyxia-induced in-hospital cardiac arrest.

Neurological and cardiac injuries are significant contributors to morbidity and mortality following pediatric in-hospital cardiac arrest (IHCA). Preservation of mitochondrial function may be critical for reducing these injuries. Dimethyl fumarate (DMF) has shown potential to enhance mitochondrial content and reduce oxidative damage. To investigate the efficacy of DMF in mitigating mitochondrial injury in a pediatric porcine model of IHCA, toddler-aged piglets were subjected to asphyxia-induced CA, followed by ventricular fibrillation, high-quality cardiopulmonary resuscitation, and random assignment to receive either DMF (30 mg/kg) or placebo for four days. Sham animals underwent similar anesthesia protocols without CA. After four days, tissues were analyzed for mitochondrial markers. In the brain, untreated CA animals exhibited a reduced expression of proteins of the oxidative phosphorylation system (CI, CIV, CV) and decreased mitochondrial respiration (p < 0.001). Despite alterations in mitochondrial content and morphology in the myocardium, as assessed per transmission electron microscopy, mitochondrial function was unchanged. DMF treatment counteracted 25% of the proteomic changes induced by CA in the brain, and preserved mitochondrial structure in the myocardium. DMF demonstrates a potential therapeutic benefit in preserving mitochondrial integrity following asphyxia-induced IHCA. Further investigation is warranted to fully elucidate DMF's protective mechanisms and optimize its therapeutic application in post-arrest care.