Plasma β2M Research Articles

Evaluation of the Effects of the Heart-Lung Machine on the Plasma Beta-2 Microglobulin Level

Purpose: In this study, it was aimed to investigate whether beta-2 microglobulin (β2M) blood plasma level is affected by cardiopulmonary bypass (CPB) and its effects on prognosis in surgeries performed using a heart-lung machine.
 
 Material and Methods: The study was carried out on 33 patients who underwent cardiac surgery using a heart-lung machine in the cardiovascular surgery department of Sivas Cumhuriyet University. Plasma β2M levels were evaluated in peripheral venous blood samples taken just before the operation, thirty minutes after connecting to the heart-lung machine, and at the twenty-fourth postoperative hour.
 
 Results: It was observed that a high β2M level was associated with long intensive care and hospital stay, prolonged intubation, increased inotrope requirement, and blood product use (P

Rapid improvement in symptoms and physical function following ibrutinib initiation in chronic lymphocytic leukemia and the associated changes in plasma cytokines

A prospective pilot study was carried out on 34 CLL patients treated with ibrutinib, evaluating the effects on symptoms and physical function with changes in plasma exosomes (EXs), β2-microglobulin (β2M) and 26 plasma cytokines. The revised Edmonton Symptom Assessment Scale (ESAS-R) demonstrated moderate fatigue, shortness of breath and a sense of unwellness before treatment, which significantly improved within 2 weeks of starting ibrutinib. These changes were associated with a rapid improvement in sit-to-stand and 4 m walking speeds. The plasma levels of CCL11, IL-7, -8 and -10 dropped initially while the levels of TNF-α/-β, CCL3, CCL4, CCL17, and IL-16 continued to decline for 12 months. Despite the initial lymphocytosis, plasma β2M levels fell but no consistent change in plasma EXs occurred. Thus, ibrutinib can produce a rapid and sustained improvement in symptoms and physical function in CLL, associated with a decline in multiple plasma cytokines.

β2M Signals Monocytes Through Non-Canonical TGFβ Receptor Signal Transduction.

Circulating monocytes can have proinflammatory or proreparative phenotypes. The endogenous signaling molecules and pathways that regulate monocyte polarization in vivo are poorly understood. We have shown that platelet-derived β2M (β-2 microglobulin) and TGF-β (transforming growth factor β) have opposing effects on monocytes by inducing inflammatory and reparative phenotypes, respectively, but each bind and signal through the same receptor. We now define the signaling pathways involved. To determine the molecular mechanisms and signal transduction pathways by which β2M and TGF-β regulate monocyte responses both in vitro and in vivo. Wild-type- (WT) and platelet-specific β2M knockout mice were treated intravenously with either β2M or TGF-β to increase plasma concentrations to those in cardiovascular diseases. Elevated plasma β2M increased proinflammatory monocytes, while increased plasma TGFβ increased proreparative monocytes. TGF-βR (TGF-β receptor) inhibition blunted monocyte responses to both β2M and TGF-β in vivo. Using imaging flow cytometry, we found that β2M decreased monocyte SMAD2/3 nuclear localization, while TGF-β promoted SMAD nuclear translocation but decreased noncanonical/inflammatory (JNK [jun kinase] and NF-κB [nuclear factor-κB] nuclear localization). This was confirmed in vitro using both imaging flow cytometry and immunoblots. β2M, but not TGF-β, promoted ubiquitination of SMAD3 and SMAD4, that inhibited their nuclear trafficking. Inhibition of ubiquitin ligase activity blocked noncanonical SMAD-independent monocyte signaling and skewed monocytes towards a proreparative monocyte response. Our findings indicate that elevated plasma β2M and TGF-β dichotomously polarize monocytes. Furthermore, these immune molecules share a common receptor but induce SMAD-dependent canonical signaling (TGF-β) versus noncanonical SMAD-independent signaling (β2M) in a ubiquitin ligase dependent manner. This work has broad implications as β2M is increased in several inflammatory conditions, while TGF-β is increased in fibrotic diseases. Graphic Abstract: A graphic abstract is available for this article.

Platelet-derived β2m regulates age related monocyte/macrophage functions.

Platelets have central roles in both immune responses and development. Stimulated platelets express leukocyte adhesion molecules and release numerous immune modulatory factors that recruit and activate leukocytes, both at the sites of activation and distantly. Monocytes are innate immune cells with dynamic immune modulatory functions that change during the aging process, a phenomenon termed “inflammaging”. We have previously shown that platelets are a major source of plasma beta-2 microglobulin (β2M) and that β2M induced a monocyte pro-inflammatory phenotype. Plasma β2M increases with age and is a pro-aging factor. We hypothesized that platelet derived β2M regulates monocyte phenotypes in the context of aging. Using wild-type (WT) and platelet specific β2M knockout mice (Plt-β2M-/-) mice, we found that plasma β2M increased with age and correlated with increased circulating Ly6CHi monocytes. However, aged Plt-β2M-/- mice had significantly fewer Ly6CHi monocytes compared to WT mice. Quantitative real-time PCR of circulating monocytes showed that WT mouse monocytes were more “pro-inflammatory” with age, while Plt-β2M-/- derived monocytes adopted a “pro-reparative” phenotype. Older Plt-β2M-/- mice had a significant decline in heart function compared to age matched WT mice, as well as increased cardiac fibrosis and pro-fibrotic markers. These data suggest that platelet-derived β2M regulates age associated monocyte polarization, and a loss of platelet derived β2M shifted monocytes and macrophages to a pro-reparative phenotype and increased pro-fibrotic cardiac responses. Platelet regulation of monocyte phenotypes via β2M may maintain a balance between inflammatory and reparative signals that affects age related physiologic outcomes.

Platelet-derived β2M regulates monocyte inflammatory responses.

β-2 Microglobulin (β2M) is a molecular chaperone for the major histocompatibility class I (MHC I) complex, hemochromatosis factor protein (HFE), and the neonatal Fc receptor (FcRn), but β2M may also have less understood chaperone-independent functions. Elevated plasma β2M has a direct role in neurocognitive decline and is a risk factor for adverse cardiovascular events. β2M mRNA is present in platelets at very high levels, and β2M is part of the activated platelet releasate. In addition to their more well-studied thrombotic functions, platelets are important immune regulatory cells that release inflammatory molecules and contribute to leukocyte trafficking, activation, and differentiation. We have now found that platelet-derived β2M is a mediator of monocyte proinflammatory differentiation through noncanonical TGFβ receptor signaling. Circulating monocytes from mice lacking β2M only in platelets (Plt-β2M-/-) had a more proreparative monocyte phenotype, in part dependent on increased platelet-derived TGFβ signaling in the absence of β2M. Using a mouse myocardial infarction (MI) model, Plt-β2M-/- mice had limited post-MI proinflammatory monocyte responses and, instead, demonstrated early proreparative monocyte differentiation, profibrotic myofibroblast responses, and a rapid decline in heart function compared with WT mice. These data demonstrate a potentially novel chaperone-independent, monocyte phenotype-regulatory function for platelet β2M and that platelet-derived 2M and TGFβ have opposing roles in monocyte differentiation that may be important in tissue injury responses.

Evidence for a Causal Role of the SH2B3-β2M Axis in Blood Pressure Regulation.

Genetic variants at SH2B3 are associated with blood pressure and circulating β2M (β-2 microglobulin), a well-characterized kidney filtration biomarker. We hypothesize that circulating β2M is an independent risk predictor of hypertension and may causally contribute to its development. The study sample consisted of 7 065 Framingham Heart Study participants with measurements of plasma β2M. Generalized estimating equations were used to test the association of β2M with prevalent and new-onset hypertension. There were 2 145 (30%) cases of prevalent hypertension at baseline and 886 (21%) cases of incident hypertension during 6 years of follow-up. A 1-SD increase in baseline plasma β2M was associated with a greater risk of prevalent (odds ratio 1.14, 95% CI 1.05-1.24) and new-onset (odds ratio 1.18, 95% CI 1.07-1.32) hypertension. Individuals within the top β2M quartile had a greater risk than the bottom quartile for prevalent (odds ratio 1.29, 95% CI 1.05-1.57) and new-onset (odds ratio 1.59, 95% CI 1.20-2.11) hypertension. These associations remained essentially unchanged in analyses restricted to participants free of albuminuria and chronic kidney disease. Mendelian randomization demonstrated that lower SH2B3 expression is causal for increased circulating β2M levels, and in a hypertensive mouse model, knockout of Sh2b3 increased β 2 M gene expression. In a community-based study of healthy individuals, higher plasma β2M levels are associated with increased risk of prevalent and incident hypertension independent of chronic kidney disease status. Overlapping genetic signals for hypertension and β2M, in conjunction with mouse knockout experiments, suggest that the SH2B3-β2M axis plays a causal role in hypertension.

Comparison of β2-microglobulin serum level between Alzheimer’s patients, cognitive healthy and mild cognitive impaired individuals

Background: Several studies performed in the last years on the brain, showed that beta2-microglobulin (β2m) and MHC can act independently of their canonical immune function to regulate normal brain development, synaptic plasticity and behaviour. Increased systemic levels of soluble β2m have been implicated in cognitive impairments like that associated with chronic haemodialysis, or aortic valve replacement. Increased soluble β2m has also been detected in the cerebral spinal fluid (CSF) of patients with HIV-associated dementia and Alzheimer’s disease (AD).Objective: To compare plasma β2m levels in healthy subjects and subjects with dementia or cognitive impairment.Methods: We measured the concentration of β2m in a cohort of 245 individuals and compared sex matched, cognitive healthy individuals.Results: We found higher levels of β2m in AD patients compared to non-AD MCI and healthy controls (2063 ng/mL ±852 versus 1613 ± 503 and 1832 ± 382 ng/mL, p< 0.001 and <0.033, respectively), while there was no difference between mild cognitive impairment (MCI) and healthy controls (p > 0.05).Conclusions: Our data confirm that β2m could play a role in AD. However, a replication study in an independent cohort would be necessary to confirm our preliminary results.

Abstract P051: Circulating Beta-2-microglobulin Predicts Cardiovascular, Cancer, and All-cause Mortality: The Framingham Heart Study

Beta-2-microglobulin (β 2 M), a multifunctional protein involved in immune function, is a filtration marker that has been reported to predict renal failure, cancer, cardiovascular disease (CVD), and all-cause mortality. Previous studies of β 2 M and mortality were limited to select study samples (elderly or patient-based) lacking information on cancer or kidney function. We examined plasma β 2 M as a predictor of all-cause and cause-specific mortality in those with and without chronic kidney disease (CKD). The study sample consisted of Framingham Heart Study participants from the 2 nd (n=3196) and 3 rd (n=3911) generations who attended an on-site examination (2001-2007). Plasma β 2 M concentration was measured using a Luminex bead-based immunoassay. Mortality events were adjudicated by a physician committee. Proportional hazard models were conducted based on standardized values of β 2 M, adjusted for CVD risk factors, prevalent CVD, cancer, and family structure. We additionally analyzed subgroups stratified for CKD (defined as GFR ckdepi &lt; 60 mL/min/1.73 m 2 ). The study sample included 7107 individuals [mean age 50 years, 54% female, 4% with prevalent CKD, mean length of follow-up: 13 years]. In the overall sample, β 2 M concentrations were associated with increased risk of CVD death (HR=1.42 [CI=1.17-1.72]), cancer death (HR=1.27 [CI=1.07-1.5]), and all-cause mortality (HR=1.27 [CI=1.16-1.4]). β 2 M performed better in participants with prevalent CKD than in those free of CKD. Adjusting for cystatin C, a filtration biomarker, did not affect the results. For all-cause mortality, including plasma β 2 M yielded a relative integrated discrimination improvement of 3% (p-value 0.03) beyond the covariate-only model. The net reclassification improvements (NRI) for all-cause mortality was 4% that was not statistically significant (p-value 0.26). We conclude that among middle-aged adults, plasma β 2 M is a predictor of all-cause and cause-specific mortality. Much of the risk associated with β 2 M is concentrated in those with CKD.

Comparison of changes in urinary and blood levels of biomarkers associated with proximal tubular injury in rat models

To investigate useful biomarkers associated with proximal tubular injury, we assessed changes in levels of a focused set of biomarkers in urine and blood. Male rats administered a single dose or four doses of gentamicin (GM, 240 mg/kg/day) or a single dose of cisplatin (CDDP, 5 mg/kg) were euthanized on days 2 (the day after initial dosing) 5, or 12. At each time point, histopathological examination of the kidney and immunohistochemistry for biomarkers, kidney injury molecule-1 (Kim-1), lipocalin (NGAL), clusterin (CLU), cystatin C (CysC) and β2-microglobulin (β2M) were performed. Biomarker levels were measured in urine and blood. In both treatment groups, degenerated/necrotic proximal tubules and regenerated tubules were mainly observed on days 5 and 12, respectively. At the same time as these tubular injuries, urinary Kim-1, CysC and β2M levels were increased. Moreover, urinary levels of CysC and β2M in GM-treated animals and Kim-1 in CDDP-treated animals increased (on day 2) prior to tubular injury on day 5. This was considered to reflect the characteristics of drug toxicity. Although almost all of the biomarkers in blood were not sufficiently sensitive to detect proximal tubular injury, urinary and plasma β2M levels simultaneously increased. Therefore, in addition to urinary Kim-1, CysC and β2M levels, plasma β2M levels were also considered useful for detecting proximal tubular injury.

Abstract 3792: Upregulation of TNF-α by ethanol extract of Moringa oleifera leaves in benzene-induced leukemic Wister rat: a possible mechanism of anticancer property

Abstract Ethanol extract of Monringa oleifera leaves has been shown to possess anticancer properties in animal models. The mechanisms of action of its anticancer properties have not been fully demonstrated. In this study, we induced leukemia in two groups of 7 rats each by intravenous injection of benzene chromasolv solution (0.2 mL) 48 hourly for 4 weeks. The extract (0.2 ml of 100 mg/mL) was administered orally by gavage, after leukemia induction, daily for 4 weeks to one of the groups while the other group was not treated. The third group served as the normal control. At the end of the treatment, the rats were immobilized by cervical dislocation and blood samples were collected by cardiac puncture. Plasma concentrations of Beta-2 Microglobulins (β2M), Perforins (PF), Interleukin-2(IL2), Interferon-gamma (IFN-γ) and Tumour Necrosis Factor-alpha (TNF-α) were determined by standard commercial ELISA Results showed that leukemia was induced within 4 weeks as a significantly elevated leukocyte count and plasma β2M concentration over the baseline were noted (p&amp;lt; 0.05). Plasma IL2 and TNF-α were also significantly elevated while PF and IFN-γ decreased significantly in Moringa oleifera leaves extract treated rats compared with untreated groups. Since IL2 and PF are associated with cytotoxicity of CD8 T lymphocytes, reduced expression of PF in the face of increasing plasma concentration of IL-2 suggests that Moringa oleifera extract may not exert its anticancer properties via direct cytotoxicity. We thus concluded that increased expression TNF-α may translate to enhanced apoptosis and may be a possible mechanism of action. Citation Format: Olufemi E. Akanni, Adebayo L. Adedeji, Kola J. Oloke. Upregulation of TNF-α by ethanol extract of Moringa oleifera leaves in benzene-induced leukemic Wister rat: a possible mechanism of anticancer property. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3792. doi:10.1158/1538-7445.AM2014-3792

β2-microglobulin, a novel biomarker of peripheral arterial disease, independently predicts aortic stiffness in these patients

Arterial stiffness is a prominent feature of vascular ageing and strongly predicts cardiovascular and total mortality. The β2-microglobulin, (β2M) a newly identified biomarker of peripheral arterial disease (PAD), is related to renal insufficiency, inflammatory and neoplastic diseases, but may also play a role in vascular dysfunction. However, the relationship between arterial stiffness and β2M has not been previously studied in patients with atherosclerosis. In the present study we examined a possible association between β2M and arterial stiffness in patients with PAD and in healthy subjects. Plasma β2M levels and parameters of arterial stiffness such as aortic pulse wave velocity (aPWV) and augmentation index (AIx) were measured in 66 patients with PAD and in 66 apparently healthy subjects. Plasma levels of β2M, aPWV and AIx were significantly increased in patients with PAD compared with controls (1858.1 ± 472.8 vs 1554.5 ± 277.9 μg/L, p < 0.001; 9.9 ± 2.2 m/s vs 7.6 ± 1.6 m/s, p < 0.001; 28 ± 8 vs 14 ± 11%, p < 0.001; respectively). There existed significant correlation between aPWV and β2M for the patient group (R = 0.47; p < 0.001), but not for the controls (R = 0.14; p = 0.26). In multivariate analysis, β2M remained independently associated with aPWV, fetuin-A, age and glomerular filtration rate in patients (R2 = 0.5, p < 0.001). We found no relationship between β2M and AIx in either group. We demonstrated that among patients with PAD elevated plasma β2M levels were associated with higher aortic stiffness irrespective of cardiovascular disease risk factors. These data suggest that β2M may influence the pathogenesis of aortic stiffness in atherosclerosis.

Mouse model to study human A β2M amyloidosis: generation of a transgenic mouse with excessive expression of human β2-microglobulin

Patients on long-term hemodialysis can develop dialysis-related amyloidosis (DRA) due to deposition of β2-microglobulin (β2m) into amyloid fibrils (Aβ2M). Despite intensive biochemical studies, the pathogenesis of amyloid deposition in DRA patients remains poorly understood. To elucidate the mechanisms that underlie Aβ2M fibril formation in DRA, we generated transgenic mice that overexpress human β2m protein in a mouse β2m gene knockout background (hB2MTg+/+ mB2m+/+). The hB2MTg+/+mB2m−/− mice express a high level of human β2m protein in many tissues as well as a high plasma β2m concentration (192.8 mg/L). This concentration is >100 times higher than that observed in healthy humans and >4 times higher than that detected in patients on dialysis. We examined spontaneous and amyloid fibril-induced amyloid deposition in these mice. Amyloid deposition of β2m protein was not observed in aged or amyloid fibril injected animals. However, mouse senile apolipoprotein A-II amyloidosis (AApoAII) was detected, particularly in the joints of mice that were injected with AApoAII amyloid fibrils.This study demonstrates that this mouse model could be valuable in studying the components and conditions that promote DRA, and indicates that high plasma concentrations of hβ2m as well as seeding with pre-existing amyloid fibrils may not be sufficient to induce Aβ2M.

Beta-2-Microglobulin in Autism Spectrum Disorders

Autism spectrum disorders (ASD) are heterogeneous neurodevelopmental diseases of unknown etiology. There are no biological markers for ASD and current diagnosis is based on behavioral criteria. Recent data has shown that MHC I, a compound involved in adaptive immune function, is also involved in neurodevelopment, synaptic plasticity and behavior. It has been suggested that altered MHC I expression could play a part in neurodevelopmental diseases like ASD. To address this possibility, we measured plasma levels of beta-2-microglobulin (I²2m), a molecule that associates with MHC I and is indicative of MHC I expression, in 36 children with autism, 28 typically developing controls and subjects with developmental disabilities (n=16) but not autism. The age range of our study population was 17-120 months. We found no statistically significant differences in plasma β2m levels between groups. Therefore, plasma levels of I²2m measured in early childhood in autism may not reflect changes in MHC class I in autism.

1497 URINARY BETA-2-MICROGLOBULIN (β2M) AS AN INDEX OF RENAL TUBLAR MATURATION IN HUMAN NEONATES

Tubular reabsorption of β2M was previously reported to increase with conceptional age (CA) and to reflect maturation of renal tubular function. To study this concept further, timed-urine collections and blood samples were obtained on 50 newborn infants (CA 28-42 wks) between 1-12 days of age. Creatinine, sodium and β2M were measured in urine and plasma; creatinine clearance (CCR) and fractional reabsorption of sodium (TNa) and β2M (Tβ2M) were calculated. Plasma β2M concentrations (3.63 ± 0.14 mg/liter, mean ± SE) did not vary with CA (r=0.085). CCR (r=0.715), TNa (r=0.627) and Tβ2M (r=0.693) increased with CA of the infants (p<0.001). Moreover, Tβ2M varied directly with TNa (r=0.474, p<0.001) and inversely with fractional urine flow rate (V/CCR) (r= -0.601, p<0.001). In serial studies of 18 infants 3.64 ± 0.67 (range 1-12) days later, changes in Tβ2M in the same infant were observed to vary inversely with changes in V/CCR (r= -0.470, p=0.05). Although the results of this study confirm previous reports that Tβ2M increases with CA of the infant, these data do not support Tβ2M as a reliable index of renal tubular maturation in the human neonate.