Identification of gravity-responsive serum proteins in spaceflight mice using a quantitative proteomic approach with data-independent acquisition mass spectrometry.

Physical inactivity associated with gravity unloading, such as microgravity during spaceflight and hindlimb unloading (HU), can cause various physiological changes. In this study, we attempted to identify serum proteins whose levels fluctuated in response to gravity unloading. First, we quantitatively assessed changes in the serum proteome profiles of spaceflight mice using mass spectrometry with data-independent acquisition. The serum levels of several proteins involved in the responses to estrogen and glucocorticoid, blood vessel maturation, osteoblast differentiation, and ossification were changed by microgravity exposure. Furthermore, a collective evaluation of serum proteomic data from spaceflight and HU mice identified 30 serum proteins, including Mmp2, Igfbp2, Tnc, Cdh5, and Pmel, whose levels varied to a similar extent in both gravity unloading models. These changes in serum levels could be involved in the physiological changes induced by gravity unloading. A collective evaluation of serum, femur, and soleus muscle proteome data of spaceflight mice also showed 24 serum proteins, including Igfbp5, Igfbp3, and Postn, whose levels could be associated with biological changes induced by microgravity. This study examined serum proteome profiles in response to gravity unloading, and may help deepen our understanding of microgravity adaptation mechanisms during prolonged spaceflight missions.

Changes in the astronaut serum proteome during prolonged spaceflight.

The molecular mechanisms associated with spaceflight-induced biological adaptations that may affect many healthy tissue functions remain poorly understood. In this study, we analyzed temporal changes in the serum proteome of six astronauts during prolonged spaceflight missions using quantitative comprehensive proteome analysis performed with the data-independent acquisition method of mass spectrometry (DIA-MS). All six astronauts participated in a spaceflight mission for approximately 6 months and showed a decreasing trend in T-scores at almost all sites where dual-energy X-ray absorptiometry scans were performed. DIA-MS successfully identified 624 nonredundant proteins in sera and further quantitative analysis for each sampling point provided information on serum protein profiles closely related to several time points before (pre-), during (in-), and after (post-) spaceflight. Changes in serum protein levels between spaceflight and on the ground suggest that abnormalities in bone metabolism are induced in astronauts during spaceflight. Furthermore, changes in the proteomic profile occurring during spaceflight suggest that serum levels of bone metabolism-related proteins, namely ALPL, COL1A1, SPP1, and POSTN, could serve as highly responsive indicators of bone metabolism status in spaceflight missions. This study will allow us to accelerate research to improve our understanding of the molecular mechanisms of biological adaptations associated with prolonged spaceflight.

Use of data-independent acquisition mass spectrometry to identify an objective serum indicator of the need for osteoporotic therapeutic intervention.

Osteoporosis is characterized by weakened bone microstructure and loss of bone mass. Current diagnostic criteria for osteoporosis are based on the T-score, which is a measure of bone mineral density. However, osteoporotic fragility fractures can occur regardless of the T-score, underscoring the need for additional criteria for the early detection of patients at fracture risk. To identify indicators of reduced bone strength, we performed serum proteomic analysis using data-independent acquisition mass spectrometry with serum samples from two patient groups, one with osteoporosis but no fractures and the other with osteopenia and fragility fractures. Collective evaluation of the results identified six serum proteins that changed to a similar extent in both patient groups compared with controls. Of these, extracellular matrix protein 1 (ECM1), which contributes to bone formation, showed the most significant increase in serum levels in both patient groups. An ELISA-based assay suggested that ECM1 could serve as a serum indicator of the need for therapeutic intervention; however, further prospective studies with a larger sample size are necessary to confirm these results. The present findings may contribute to the provision of early and appropriate therapeutic strategies for patients at risk of osteoporotic fractures. SIGNIFICANCE: This study aimed to identify objective serum indicators of the need for therapeutic intervention in individuals at risk of osteoporotic fracture. Comprehensive proteome analyses of serum collected from patients with osteoporosis but no fractures, patients with osteopenia and fragility fractures, and controls were performed by data-independent acquisition mass spectrometry. Collective evaluation of the proteome analysis data and ELISA-based assays identified serum ECM1 as a potential objective marker of the risk of fragility fractures in patients with osteoporosis or osteopenia. The findings are an important step toward the development of appropriate bone health management methods to improve well-being and maintain quality of life.

Identification of mouse soleus muscle proteins altered in response to changes in gravity loading.

Gravity-dependent physical processes strongly affect the ability of elderly people to maintain musculoskeletal health by reducing muscle atrophy and increasing bone mineral density, thereby increasing quality of life. A need therefore exists to identify molecules in the musculoskeletal system that are responsive to gravitational loading and to establish an objective indicator for the maintenance of healthy musculoskeletal systems. Here, we performed an integrated assessment of the results of soleus muscle proteomic analyses in three model mouse experiments under different gravity environments (hypergravity, hindlimb unloading, and spaceflight). Myl6b, Gpd1, Fbp2, Pvalb, and Actn3 were shown to be gravity-responsive muscle proteins, and alterations in the levels of these proteins indicated changes in muscle fiber type to slow-twitch type due to gravity loading. In addition, immunoblotting and enzyme-linked immunosorbent assays revealed that Pvalb levels in the sera of hindlimb-unloaded mice and osteoporosis patients were higher than in control subjects, suggesting that Pvalb levels might be useful to objectively evaluate soleus muscle atrophy and bone loss.

Identification of gravity-responsive proteins in the femur of spaceflight mice using a quantitative proteomic approach.

Although the microgravity (µ-g) environment that astronauts encounter during spaceflight can cause severe acute bone loss, the molecular mechanism of this bone loss remains unclear. To investigate the gravity-response proteins involved in bone metabolism, it is important to comprehensively determine which proteins exhibit differential abundance associated with mechanical stimuli. However, comprehensive proteomic analysis using small bone samples is difficult because protein extraction in mineralized bone tissue is inefficient. Here, we established a high-sensitivity analysis system for mouse bone proteins using data-independent acquisition mass spectrometry. This system successfully detected 40 proteins in the femoral diaphysis showing differential abundance between mice raised in a µ-g environment, where the bone mass was reduced by gravity unloading, and mice raised in an artificial 1-gravity environment on the International Space Station. Additionally, 22 proteins, including noncollagenous bone matrix proteins, showed similar abundance between the two groups in the mandible, where bone mass was unaltered due to mastication stimuli, suggesting that these proteins are responsive to mechanical stimuli. One of these proteins, SPARCL1, is suggested to promote osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand. We expect these findings to lead to new insights into the mechanisms of bone metabolism induced by mechanical stimuli. SIGNIFICANCE: We aimed to investigate the gravity-response proteins involved in bone metabolism. To this end, we established a comprehensive analysis system for mouse bone proteins using data-independent acquisition mass spectrometry, which is particularly useful in comprehensively analyzing the bone proteome using small sample volumes. In addition, a comprehensive proteomic analysis of the femoral diaphysis and mandible, which exhibit different degrees of bone loss in mice raised on the International Space Station, identified proteins that respond to mechanical stimuli. SPARCL1, a mechanical stimulus-responsive protein, was consequently suggested to be involved in osteoclast differentiation associated with bone remodeling. Our findings represent an important step toward elucidating the molecular mechanism of bone metabolism induced by mechanical stimuli.

Identification of serum prognostic biomarkers of severe COVID-19 using a quantitative proteomic approach.

The COVID-19 pandemic is an unprecedented threat to humanity that has provoked global health concerns. Since the etiopathogenesis of this illness is not fully characterized, the prognostic factors enabling treatment decisions have not been well documented. Accurately predicting the progression of the disease would aid in appropriate patient categorization and thus help determine the best treatment option. Here, we have introduced a proteomic approach utilizing data-independent acquisition mass spectrometry (DIA-MS) to identify the serum proteins that are closely associated with COVID-19 prognosis. Twenty-seven proteins were differentially expressed between severely ill COVID-19 patients with an adverse or favorable prognosis. Ingenuity Pathway Analysis revealed that 15 of the 27 proteins might be regulated by cytokine signaling relevant to interleukin (IL)-1ß, IL-6, and tumor necrosis factor (TNF), and their differential expression was implicated in the systemic inflammatory response and in cardiovascular disorders. We further evaluated practical predictors of the clinical prognosis of severe COVID-19 patients. Subsequent ELISA assays revealed that CHI3L1 and IGFALS may serve as highly sensitive prognostic markers. Our findings can help formulate a diagnostic approach for accurately identifying COVID-19 patients with severe disease and for providing appropriate treatment based on their predicted prognosis.

New horny layer marker proteins for evaluating skin condition in atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) has a complicated pathogenesis and its clinical features vary greatly among patients. Although many clinical parameters have been reported, it remains difficult to evaluate AD skin conditions adequately. OBJECTIVE: To support better evaluation of AD patients, we attempted to develop a new, objective and noninvasive method that assesses skin condition in AD using biochemical markers in the skin's horny layer (HL). METHODS: Thirty-six patients with AD, 8 with psoriasis and 16 healthy volunteers were recruited. HL samples were obtained by tape stripping from involved and uninvolved skin of the forearms. Expression levels of 6 proteins in the HL [fatty acid-binding protein-5 (FABP-5), squamous cell carcinoma antigens 2 (SCCA2), alpha-enolase, annexin II, apolipoprotein A-I and albumin] were analyzed by immunoblotting and compared with clinical data. RESULTS: The 6 proteins were detected at a high level in AD skin lesions, but scarcely in the normal controls. FABP-5 showed correlation with the local severity of the involved skin. Annexin II, apoprotein A-I and albumin showed correlation with the severity of specific eruptions. SCCA2 correlated significantly with total serum IgE level. Albumin levels in the uninvolved skin of AD patients showed significant correlation with the local severity in the involved skin of the same patient and with the trans-epidermal water loss. Albumin levels in psoriatic skin were very low, even with scratch marks, compared to those in AD skin. CONCLUSION: FABP-5, albumin and some other proteins in HL seem to be useful as biomarkers to evaluate inflammation and skin barrier conditions in AD patients.

Nephrotic syndrome and aberrant expression of laminin isoforms in glomerular basement membranes for an infant with Herlitz junctional epidermolysis bullosa.

Herlitz junctional epidermolysis bullosa (H-JEB) is a hereditary bullous disease caused by absent expression of laminin-5, a component of anchoring filaments within the dermal-epidermal basement membrane zone. Affected individuals usually die during the first 1 year of life. We studied an infant with H-JEB who presented with nephrotic syndrome, a previously unreported complication that may contribute to early death in this disease. DNA analysis revealed a compound heterozygote for mutations 2379delG and Q995X in the LAMB3 gene. The patient had massive albuminuria, attributable to failure of the glomerular filtration barrier, and high urinary N-acetylglucosaminidase levels, indicating renal tubular involvement. Electron-microscopic examination of the renal tissue revealed diffuse fusion of the foot processes, irregular swelling of the lamina rara interna, and disappearance of endothelial cell fenestrations. Immunohistopathologic analysis of the patient's renal tissue revealed compositional changes in laminin isoforms of the glomerular basement membrane and no detectable laminin-5 in the renal tubular basement membrane, which suggests that laminin-5 may play an important role in renal function. Our findings strongly suggest that H-JEB should be considered in the spectrum of congenital nephrotic syndromes. Combination therapy with meticulous skin care and treatment strategies established for congenital nephrotic syndromes may rescue patients with this disease.

Laminin-6 is activated by proteolytic processing and regulates cellular adhesion and migration differently from laminin-5.

Laminin-6 (LN6) and laminin-5 (LN5), which share the common integrin-binding domain in the laminin alpha3 chain, are thought to cooperatively regulate cellular functions, but the former has poorly been characterized. Human fibrosarcoma HT1080 cells expressing an exogenous alpha3 chain were found to secrete LN6 with the full-length alpha3 chain and a smaller amount of its processed form lacking the carboxyl-terminal G4-5 domain, besides mature LN5 without G4-5 (mat-LN5). We prepared the unprocessed LN6 and mat-LN5, as well as LN6 mutants without G4-5 (LN6DeltaG4-5) or G5 (LN6DeltaG5). These laminins supported attachment of HT1080 cells and human keratinocytes (HaCaT) through integrins alpha(3)beta(1) and/or alpha(6)beta(1). LN6DeltaG4-5, LN6DeltaG5, and mat-LN5 promoted rapid cell spreading, whereas LN6 did hardly. A purified G4-5 fragment of the laminin alpha3 chain supported cell attachment through interaction with heparan sulfate proteoglycans and promoted cell spreading in combination with mat-LN5 or LN6DeltaG4-5. These results imply that the G4-5 domain within the LN6 molecule suppresses cell adhesion, while the released G4-5 promotes it. The presence of G5 rather than the heparin-binding domain G4 was responsible for the impaired cell spreading activity of LN6. However, the unprocessed LN6 promoted cell spreading in the presence of mat-LN5. Unlike mat-LN5, both LN6DeltaG4-5 and LN6 did weakly or did not stimulate cell motility. These findings demonstrate that LN6 and LN5 have distinct biological activities, but they may cooperatively support cell adhesion. The proteolytic processing of the alpha3 chain seems to regulate the physiological functions of LN6.