High Glucose Impairs Expression and Activation of MerTK in ARPE-19 Cells

MerTK (Mer Tyrosine Kinase) is a cell surface receptor that regulates phagocytosis of pho-toreceptor outer segments (POS) in retinal pigment epithelial (RPE) cells. POS phagocytosis is im-paired in several pathologies, including diabetes. In this study, we investigate whether hyperglyce-mic conditions may affect MerTK expression and activation in ARPE-19 cells, a retinal pigment epithelial cellular model. ARPE-19 cells were cultured in standard (CTR) or high-glucose (HG) me-dium for 24 h. Then, we analyzed: mRNA levels and protein expression of MerTK and ADAM9, a protease that cleaves the extracellular region of MerTK; the amount of cleaved Mer (sMer); and the ability of GAS6, a MerTK ligand, to induce MerTK phosphorylation. Since HG reduces miR-126 levels, and ADAM9 is a target of miR-126, ARPE-19 cells were transfected with miR-126 inhibitor or mimic; then, we evaluated ADAM9 expression, sMer, and POS phagocytosis. We found that HG reduced expression and activation of MerTK. Contextually, HG increased expression of ADAM9 and the amount of sMer. Overexpression of miR-126 reduced levels of sMer and improved phago-cytosis in ARPE-19 cells cultured with HG. In this study, we demonstrate that HG compromises MerTK expression and activation in ARPE-19 cells. Our results suggest that HG up-regulates ADAM9 expression, leading to increased shedding of MerTK. The consequent rise in sMer coupled to reduced expression of MerTK impairs binding and internalization of POS in ARPE-19 cells

Shoulder hemiarthroplasty for fractures of the proximal humerus

Proximal humeral fractures were managed with primary hemiarthroplasty in 57 patients, 53 women (93%) and 4 men (7%) aged 51–87 years (mean 72.2). The mean follow-up period was 52 months (range 12–98), and the mean Constant score was 59.2 (range 38–76). Patients were very satisfied (n = 19); satisfied (n = 32) or dissatisfied with the outcome (n = 5). One patient required early revision surgery. Surgical treatment of three- and four-part fractures of the proximal humerus with hemiarthroplasty is a safe and effective approach, the outcome of which appears to be related to the quality of the anatomical reconstruction of the tuberosities

Antioxidant role of metallothioneins: a comparatie overview.

Metallothioneins (MTs) are sulfhydryl-rich proteins binding essential and non-essential heavy metals. MTs display in vitro oxyradical scavenging capacity, suggesting that they may specifically neutralize hydroxyl radicals. Yet, this is probably an oversimplified view, as MTs represent a superfamily of widely differentiated metalloproteins. MT antioxidant properties mainly derive from sulfhydryl nucleophilicity, but also from metal complexation. Binding of transition metals displaying Fenton reactivity (Fe,Cu) can reduce oxidative stress, whereas their release exacerbates it. In vertebrates, MT gene promoters contain metal (MRE) and glucocorticoid response elements (GRE), Sp and AP sequences, but also antioxidant response elements (ARE). MT neosynthesis is induced by heavy metals, cytokines, hormones, but also by different oxidants and prooxidants. Accordingly, MT overexpression increases the resistance of tissues and cells to oxidative stress. As for invertebrates, data from the mussel show that MT can actually protect against oxidative stress, but is poorly inducible by oxidants. In yeast, there is a Cu(I)-MT that in contrast to mammalCu-MT exhibits antioxidant activity, possibly due to differences in metal binding domains. Finally, as the relevance of redox processes in cell signaling is becoming more and more evident, a search for MT effects on redox signaling could represent a turning point in the understanding of the functional role of these protein

The hormetic effect of metformin: \u201cless is more\u201d?

Metformin (MTF) is the first-line therapy for type 2 diabetes (T2DM). The euglycemic effect of MTF is due to the inhibition of hepatic glucose production. Literature reports that the principal molecular mechanism of MTF is the activation of 5\u2032-AMP-activated protein kinase (AMPK) due to the decrement of ATP intracellular content consequent to the inhibition of Complex I, although this effect is obtained only at millimolar concentrations. Conversely, micromolar MTF seems to activate the mitochondrial electron transport chain, increasing ATP production and limiting oxidative stress. This evidence sustains the idea that MTF exerts a hormetic effect based on its concentration in the target tissue. Therefore, in this review we describe the effects of MTF on T2DM on the principal target organs, such as liver, gut, adipose tissue, endothelium, heart, and skeletal muscle. In particular, data indicate that all organs, except the gut, accumulate MTF in the micromolar range when administered in therapeutic doses, unmasking molecular mechanisms that do not depend on Complex I inhibition

Hamstrings anterior cruciate ligament reconstruction with and without platelet rich fibrin matrix

Anterior cruciate ligament (ACL) rupture is the most common complete ligamentous injury in the knee. Many studies explored ACL graft integration and maturation, but only a few assessed the application of platelet rich fibrin matrix (PRFM) as augmentation for ACL reconstruction. The main aim of this study was to test the PRFM augmentation in terms of graft-bone integration and knee stability. The secondary aim was to investigate patient-reported functional status.Prospective evaluation has been done in two consecutive series of patients who underwent ACL reconstruction with semitendinosus and gracilis (STG) grafts: 14 patients were operated with PRFM augmentation and 14 patients without PRFM augmentation. Objective clinical evaluation (Rolimeter) and MRI evaluation were performed at 1 year from surgery. Subjective evaluation (IKDC) was performed pre-operatively and at 6 months, 1 and 2 years from surgery.A statistically significant difference was not detected between the two groups in terms of MRI and objective clinical evaluation, although PRFM-augmented patients showed a statistically significant higher clinical improvement.The procedure described for PRFM augmentation in ACL STG reconstruction does not improve radiologic graft integration and knee stability after 1 year and should not be used by clinicians to this purpose. However, it may result in a short-term improvement of patient-reported knee function, and future research should focus on further developing PRP treatment to optimize ACL clinical outcome. LEVEL OF EVIDENCE: III

Platelet-rich plasma augmentation for arthroscopic rotator cuff repair: a randomized controlled trial.

BACKGROUND: After reinsertion on the humerus, the rotator cuff has limited ability to heal. Growth factor augmentation has been proposed to enhance healing in such procedure. PURPOSE: This study was conducted to assess the efficacy and safety of growth factor augmentation during rotator cuff repair. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Eighty-eight patients with a rotator cuff tear were randomly assigned by a computer-generated sequence to receive arthroscopic rotator cuff repair without (n = 45) or with (n = 43) augmentation with autologous platelet-rich fibrin matrix (PRFM). The primary end point was the postoperative difference in the Constant score between the 2 groups. The secondary end point was the integrity of the repaired rotator cuff, as evaluated by magnetic resonance imaging. Analysis was on an intention-to-treat basis. RESULTS: All the patients completed follow-up at 16 months. There was no statistically significant difference in total Constant score when comparing the results of arthroscopic repair of the 2 groups (95% confidence interval, -3.43 to 3.9) (P = .44). There was no statistically significant difference in magnetic resonance imaging tendon score when comparing arthroscopic repair with or without PRFM (P = .07). CONCLUSION: Our study does not support the use of autologous PRFM for augmentation of a double-row repair of a small or medium rotator cuff tear to improve the healing of the rotator cuff. Our results are applicable to small and medium rotator cuff tears; it is possible that PRFM may be beneficial for large and massive rotator cuff tears. Also, given the heterogeneity of PRFM preparation products available on the market, it is possible that other preparations may be more effective

Impairment of extramitochondrial oxidative phosphorylation in mouse rod outer segments by blue light irradiation

Exposure to short wavelength light causes increased reactive oxygen intermediates production in the outer retina, particularly in the rod Outer Segments (OS). Consistently, the OS were shown to conduct aerobic ATP production through the ectopic expression of the electron transfer chain complexes I-IV and F1Fo-ATP synthase. These facts prompted us to verify if the oxidative phosphorylation in the OS is implied in the oxidative damage of the blue-light (BL) treated OS, in an organotypic model of mouse retina. Whole mouse eyeball cultures were treated with short wavelength BL (peak at 405 nm, output power 1 mW/cm2) for 6 h. Immunogold transmission electron microscopy confirmed the expression of Complex I and F1Fo-ATP synthase in the OS. In situ histochemical assays on unfixed sections showed impairment of respiratory Complexes I and II after BL exposure, both in the OS and IS, utilized as a control. Basal O2 consumption and ATP synthesis were impaired in the OS purified from blue-light irradiated eyeball cultures. Electron transfer capacity between Complex I and II as well as activity of Complexes I and II was decreased in blue-light irradiated purified OS. The severe malfunctioning of the OS aerobic respiratory capacity after 6 h BL treatment may be the consequence of a self-induced damage. BL exposure would cause an initial over-functioning of both the phototransduction and respiratory chain, with reactive oxygen species production. In a self-renewal vicious cycle, membrane and protein oxidative damage, proton leakage and uncoupling, would impair redox chains, perpetuating the damage and causing hypo-metabolism with eventual apoptosis of the rod. Data may shed new light on the rod-driven retinopathies such as Age Related Macular Degeneration, of which blue-light irradiated retina represents a model