BDE-154 Induces Mitochondrial Permeability Transition and Impairs Mitochondrial Bioenergetics

Brominated flame retardants are used in various consumer goods to make these materials difficult to burn. Polybrominated diphenyl ethers (PBDE), which are representative of this class of retardants, consist of two benzene rings linked by an oxygen atom, and contain between 1 and 10 bromine atoms in their chemical structure, with the possibility of up to 209 different congeners. Among these congeners, BDE-154 (hexa-BDE) is persistent in the environment and easy to detect in the biota, but no apparent information regarding the mechanism underlying action and toxicity is available. Mitochondria, as the main energy-producing organelles, play an important role in the maintenance of various cellular functions. Therefore, mitochondria were used in the present study as an experimental model to determine the effects of BDE-154 congener at concentrations ranging from 0.1 μM to 50 μM. Our results demonstrated that BDE-154 interacts with the mitochondrial membrane, preferably by inserting into the hydrophobic core of the mitochondrial membrane, which partially inhibits respiration, dissipates Δψ, and permeabilizes the inner mitochondrial membrane to deplete ATP. These effects are more pronounced at concentrations equal to or higher than 10 μM. Results also showed that BDE-154 did not induce reactive oxygen species (ROS) accumulation within the mitochondria, indicating the absence of oxidative stress. Therefore, BDE-154 impairs mitochondrial bioenergetics and permeabilizes the mitochondrial membrane, potentially leading to cell death but not via mechanisms involving oxidative stress.     

Regulatory authorities and orthopaedic clinical trials on expanded mesenchymal stem cells

Skeletal injuries requiring bone augmentation techniques are increasing in the context of avoiding or treating difficult cases with bone defects, bone healing problems, and bone regeneration limitations. Musculoskeletal severe trauma, osteoporosis-related fractures, and conditions where bone defect, bone collapse or insufficient bone regeneration occur are prone to disability and serious complications. Bone cell therapy has emerged as a promising technique to augment and promote bone regeneration. Interest in the orthopaedic community is considerable, although many aspects related to the research of this technique in specific indications may be insufficiently recognised by many orthopaedic surgeons. Clinical trials are the ultimate research in real patients that may confirm or refute the value of this new therapy. However, before launching the required trials in bone cell therapy towards bone regeneration, preclinical data is needed with the cell product to be implanted in patients to ensure safety and efficacy. These preclinical studies support the end-points that need to be evaluated in clinical trials. Orthopaedic surgeons are the ultimate players that, through their research, would confirm in clinical trials the benefit of bone cell therapies. To further foster this research, the pathway to eventually obtain authorisation from the National Competent Authorities and Research Ethics Committees under the European regulation is reviewed, and the experience of the REBORNE European project offers information and important clues about the current Voluntary Harmonization Procedure and other opportunities that need to be considered by surgeons and researchers on the topic.     

Biocompatibility of Ricinus communis polymer with addition of calcium carbonate compared to titanium. Experimental study in guinea pigs

Objective

The aim of the present investigation was to determine whether the difference in inflammatory tissue reaction between the Riccinus communis (castor) polymer with calcium carbonate and the titanium implant is statistically significant.

Methods

Thirty-two Cavia porcellus were allocated into four groups of eight animals each. We implanted the two types of materials in the retroperitoneal space of all the animals. They were euthanized at 7, 20, 30 and 40 days after surgery, and an histological study of the samples was conducted.

Results

All implants showed characteristics of chronic inflammation regardless of the material and timepoint of evaluation. There was no statistically significant difference between Pm+CaCO₃ and Ti with regard to the presence of granulation tissue, tissue congestion, histiocytes, lymphocytes, neutrophils, giant cells, and fibrosis (P> 0.05).

Conclusion

The castor oil polymer plus calcium carbonate implant was not statistically different from the titanium implant regarding inflammatory tissue reaction.     

Effects of LED phototherapy on relative wound contraction and reepithelialization during tissue repair in hypothyroid rats: morphometric and histological study

The aim of this study was to assess morphometrically and histologically, the effects of light-emitting diode (LED) (λ630?±?20 nm) phototherapy on reepithelialization and wound contraction during tissue repair in hypothyroid rats. Thyroid hormone deficiency has been associated with disorders of tissue repair. LED phototherapy has been studied using several healing models, but their usefulness in the improvement of hypothyroidism wound healing remains unknown. Under general anesthesia, a standard surgical wound (1 cm²) was produced on the dorsum of 48 male Wistar rats divided into four groups of 12 animals each: EC—control euthyroid, ED—euthyroid + LED, HC—control hypothyroid, and HD—Hypothyroid + LED. The irradiation started immediately after surgery and was repeated every other day for 7 and 14 days. Photographs of the wound were taken at the day of the surgical procedure and on days 8 and 15 after surgery, when animals’ deaths occurred. The specimens were removed, routinely processed, and stained with hematoxylin/eosin. Seven days after the surgery, it was possible to observe statistically significant reductions in the wound area of the irradiated euthyroid group, in comparison to hypothyroid group, irradiated and non-irradiated (ANOVA, p?<?0.05). The reepithelialization was significantly higher in the euthyroid and hypothyroid groups irradiated with LED than in the non-irradiated groups (Fisher’s test, p?<?0.05). No significant difference was found in the experimental period of 14 days among the groups. The hypothyroidism delayed wound healing and the LED phototherapy, at these specific parameters, improved the process of reepithelialization in the presence of hypothyroidism.     

Lung ultrasound during hemodialysis: the role in the assessment of volume status

Objective

Fluid balance is important in patients undergoing hemodialysis. “Dry” weight is usually estimated clinically, and also, bioimpedance is considered reliable. Ultrasonography of inferior vena cava (IVC) estimates central venous pressure, and lung ultrasound evaluates extravascular (counting B-lines artifact) lung water. Our study was aimed to clarify their usefulness in the assessment of volume status during hemodialysis.

Methods

A total of 71 consecutive patients undergoing hemodialysis underwent lung and IVC ultrasound and bioimpedance spectroscopy immediately before and after dialysis.

Results

There was a significant reduction in the number of B-lines (3.13 vs 1.41) and in IVC diameters (end-expiratory diameter 1.71 vs 1.37; end-inspiratory diameter 1.19 vs 0.95) during dialysis. The reduction in B-lines correlated with weight reduction during dialysis (p 0.007); none of the parameters concerning the IVC correlated with fluid removal. At the end of the dialysis session, the total number of B-lines correlated with bioimpedance residual weight (p 0.002).

Discussion

The reduction in B-lines correlated with fluid loss due to hemodialysis, despite the small pre-dialysis number, confirming that lung ultrasound can identify even modest variations in extravascular lung water. IVC ultrasound, which reflects the intravascular filling grade, might not be sensitive enough to detect rapid volume decrease. Clinically estimated dry weight had a poor correlation with both bioimpedance and ultrasound techniques. Post-dialysis B-lines number correlates with residual weight assessed with bioimpedance, suggesting a role for ultrasound in managing hemodialysis patients.     

Functional Role of Glucose Metabolism,Osmotic Stress,and Sodium-Glucose Cotransporter Isoform-Mediated Transport on Na+/H+ Exchanger Isoform 3 Activity in the Renal Proximal Tubule

Na⁺-glucose cotransporter 1 (SGLT1)-mediated glucose uptake leads to activation of Na⁺-H⁺ exchanger 3 (NHE3) in the intestine by a process that is not dependent on glucose metabolism. This coactivation may be important for postprandial nutrient uptake. However, it remains to be determined whether SGLT-mediated glucose uptake regulates NHE3-mediated NaHCO₃ reabsorption in the renal proximal tubule. Considering that this nephron segment also expresses SGLT2 and that the kidneys and intestine show significant variations in daily glucose availability, the goal of this study was to determine the effect of SGLT-mediated glucose uptake on NHE3 activity in the renal proximal tubule. Stationary in vivo microperfusion experiments showed that luminal perfusion with 5 mM glucose stimulates NHE3-mediated bicarbonate reabsorption. This stimulatory effect was mediated by glycolytic metabolism but not through ATP production. Conversely, luminal perfusion with 40 mM glucose inhibited NHE3 because of cell swelling. Notably, pharmacologic inhibition of SGLT activity by Phlorizin produced a marked inhibition of NHE3, even in the absence of glucose. Furthermore, immunofluorescence experiments showed that NHE3 colocalizes with SGLT2 but not SGLT1 in the rat renal proximal tubule. Collectively, these findings show that glucose exerts a bimodal effect on NHE3. The physiologic metabolism of glucose stimulates NHE3 transport activity, whereas, supraphysiologic glucose concentrations inhibit this exchanger. Additionally, Phlorizin-sensitive SGLT transporters and NHE3 interact functionally in the proximal tubule.The kidney proximal tubule (PT) is the site where the reabsorption of approximately 70% of filtered sodium bicarbonate occurs. It is mainly performed by the Na⁺/H⁺ exchanger isoform 3 (NHE3).¹ The physiologic importance of NHE3 became evident after the development of NHE3 knockout mice, which presented mild metabolic acidosis and volume depletion with reduced BP, underscoring the role of NHE3 in volume homeostasis.²It has been shown that NHE3 physically and functionally interacts with dipeptidyl-peptidase IV, an enzyme that degrades and inactivates the incretin hormone glucagon like peptide-1.³ The inhibition of dipeptidyl-peptidase IV and the action of glucagon like peptide-1 were shown to inhibit NHE3 and promote natriuresis.^3–8 Additionally, various conditions and substances related to glucose metabolism, including diabetes, insulin, ATP, and glucose, modulate NHE3 in different tissues, showing a close relationship between carbohydrate homeostasis and NHE3 activity.^9–12Plasma glucose concentration is maintained at a constant level by a complex system, in which the kidneys perform a pivotal role by reabsorbing all the filtered glucose in the PT.¹³ In addition, the kidneys and liver are the only organs that express the glucose-6-phosphatase enzyme, thus enabling them to perform gluconeogenesis.^14,15 This enzyme is only expressed in the PT,¹⁶ highlighting the importance of this kidney segment in carbohydrate metabolism.It has been shown that the kidneys metabolize 20% of the glucose consumed in a meal.¹⁴ The PT has a low expression of hexokinase but the highest concentration and activity of glucose-6-phosphate dehydrogenase, indicating that this segment is able to metabolize glucose.^16,17 However, it is currently believed that the PT uses noncarbohydrate compounds as energy sources.¹⁷With relation to glucose uptake, the majority of filtered glucose is reabsorbed by the low-affinity, high-capacity sodium-glucose cotransporter isoform 2 (SGLT2). Some glucose is also reabsorbed by the high-affinity, low-capacity sodium-glucose cotransporter isoform 1 (SGLT1).¹³ Recently, SGLT2 inhibitors have been approved for the treatment of hyperglycemia in diabetic patients. The use of these inhibitors has been shown to decrease blood glucose, glycated hemoglobin, postprandial glucose, insulinemia, and body weight.^18–20The role of glucose uptake in the modulation of NHE3 activity in the small intestine has been extensively studied. Experiments have shown that glucose uptake through SGLT1 promotes intracellular NHE3-dependent alkalinization.^21–26 However, functional differences between intestinal and renal NaHCO₃ NHE3-mediated reabsorption have not been established. These two systems differ physiologically, because the gastrointestinal system is exposed to fluctuations in glucose concentration between the periods of fasting and after meals.¹³ The presence of large amounts of solutes within the intestinal cells after meals modulates membrane transporters, such as glucose transporter 2 (GLUT2) and NHE3,^21,27 an important process for nutrient absorption.Although the synergistic activation between SGLT1 and NHE3 has been observed in the intestine,²¹ it is not known if this process also occurs in the kidneys. Considering that the kidneys also express SGLT2 and the particularities of glucose availability in this organ, the goal of the present work was to determine the effect of glucose and SGLT activity on NHE3 in the renal PT.