Unexplored Roles of Erythrocytes in Atherothrombotic Stroke.

Stroke constitutes the second highest cause of morbidity and mortality worldwide while also impacting the world economy, triggering substantial financial burden in national health systems. High levels of blood glucose, homocysteine, and cholesterol are causative factors for atherothrombosis. These molecules induce erythrocyte dysfunction, which can culminate in atherosclerosis, thrombosis, thrombus stabilization, and post-stroke hypoxia. Glucose, toxic lipids, and homocysteine result in erythrocyte oxidative stress. This leads to phosphatidylserine exposure, promoting phagocytosis. Phagocytosis by endothelial cells, intraplaque macrophages, and vascular smooth muscle cells contribute to the expansion of the atherosclerotic plaque. In addition, oxidative stress-induced erythrocytes and endothelial cell arginase upregulation limit the pool for nitric oxide synthesis, leading to endothelial activation. Increased arginase activity may also lead to the formation of polyamines, which limit the deformability of red blood cells, hence facilitating erythrophagocytosis. Erythrocytes can also participate in the activation of platelets through the release of ADP and ATP and the activation of death receptors and pro-thrombin. Damaged erythrocytes can also associate with neutrophil extracellular traps and subsequently activate T lymphocytes. In addition, reduced levels of CD47 protein in the surface of red blood cells can also lead to erythrophagocytosis and a reduced association with fibrinogen. In the ischemic tissue, impaired erythrocyte 2,3 biphosphoglycerate, because of obesity or aging, can also favor hypoxic brain inflammation, while the release of damage molecules can lead to further erythrocyte dysfunction and death.

Red Blood Cell Malfunction in COVID-19: Molecular Mechanisms and Therapeutic Targets.

The world has been facing a pandemic for the past 2 years. COVID-19 still leads to millions of deaths worldwide, while deteriorating the global economy. The need for therapeutic targets, thus, remains. Interestingly, red blood cells, apart from gas exchange, also serve as modulators of innate and adaptive immunity. This function is accommodated mainly by surface molecules (proteins, lipids, and carbohydrates) and increased antioxidant capacity. However, under the circumstances of a disease state, red blood cells can become proinflammatory cells. Recent evidence has shown that, in the context of COVID-19, erythrocytes present protein oxidation, decreased antioxidant capacity, increased glycolysis, altered membrane lipidome, increased binding of Cytosine-Guanine (CpG) DNA and complement proteins, and low CD47 levels. These changes lead to an erythrocyte-dependent inflammation, which possibly participates in the hyperinflammation status of COVID-19. The current knowledge for the dysfunction of red blood cells during COVID-19 implies that the BAND3 protein and toll-like receptor 9 are potential therapeutic targets for COVID-19.

Red Blood Cell-Conditioned Media from Non-Alcoholic Fatty Liver Disease Patients Contain Increased MCP1 and Induce TNF-α Release.

Background: Non-alcoholic fatty liver disease (NAFLD) constitutes a global pandemic. An intricate network among cytokines and lipids possesses a central role in NAFLD pathogenesis. Red blood cells comprise an important source of both cytokines and signaling lipids and have an important role in molecular crosstalk during immunometabolic deregulation. However, their role in NAFLD has not been thoroughly investigated. Methods: Conditioned media from erythrocytes derived from 10 NAFLD patients (4 men, 6 women, aged 57.875±15.16) and 10 healthy controls (4 men, 6 women, aged 39.3±15.55) was analyzed for the cytokines IFN-γ, TNF-α, CCL2, CCL5, IL-8, IL-1ß, IL-12p40, IL-17, MIP-1ß, the signaling lipids sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA), and cholesterol. Their effect on the cytokine profile released by RAW 264.7 macrophages was also studied. Results: MCP1 levels were greater in conditioned growth medium from NAFLD patient erythrocytes than in that from healthy controls (37±40 vs 6.51±5.63 pg/ml). No statistically significant differences were found between patients and healthy controls with regard to S1P, LPA, cholesterol, or eight other cytokines. TNF-a release by RAW 264.7 cells was greater after incubation with patient-derived erythrocyte-conditioned medium than in medium without RAW 264.7 cells from either healthy or NAFLD subjects. Conclusion: Erythrocytes may contribute to liver infiltration by monocytes, and macrophage activation, partially due to CCL2 release, in the context of NAFLD..

Nonalcoholic Fatty Liver Disease Patients Exhibit Reduced CD47 and Increased Sphingosine, Cholesterol, and Monocyte Chemoattractant Protein-1 Levels in the Erythrocyte Membranes.

Background: Nonalcoholic fatty liver disease (NAFLD) constitutes a significant cause of deaths, liver transplantations, and economic costs worldwide. Despite extended research, investigations on the role of erythrocytes are scarce. Red blood cells from experimental animals and human patients with NAFLD present phosphatidylserine exposure, which is then recognized by Kupffer cells. This event leads to erythrophagocytosis and amplification of inflammation through iron disposition. In addition, it has been shown that erythrocytes from NAFLD patients release the chemokine monocyte chemoattractant protein-1 (MCP1), leading to increased tumor necrosis factor alpha release from macrophages RAW 264.7. However, erythrophagocytosis can also be caused by reduced CD47 levels. Moreover, increased MCP1 release could be either signal-induced or caused by higher MCP1 levels on the erythrocyte membrane. Finally, erythrocyte efferocytosis could provide additional inflammatory metabolites. Methods: In this study, we measured the erythrocyte membrane levels of CD47 and MCP1 by enzyme-linked immunosorbent assay, and cholesterol and sphingosine with thin-layer chromatography. Eighteen patients (8 men and 10 women, aged 56.7 ± 11.5 years) and 14 healthy controls (7 men and 7 women, aged 39.3 ± 15.6 years) participated in our study. Results: The erythrocyte CD47 levels were decreased in the erythrocyte membranes of NAFLD patients (844 ± 409 pg/mL) compared with healthy controls (2969 ± 1936 pg/mL) with P = 0.012. Levels of MCP1 increased in NAFLD patients (389 ± 255 pg/mL) compared with healthy controls (230 ± 117 pg/mL) with P = 0.0274, but low statistical power. Moreover, in erythrocyte membranes, there was a statistically significant accumulation of sphingosine and cholesterol in NAFLD patients compared with healthy controls. Conclusions: Our results imply that erythrocytes release chemotactic "find me" signals (MCP1) while containing reduced "do not eat me" signals (CD47). These molecules can lead to erythrophagocytosis. Next, increased "goodbye" signals (sphingosine and cholesterol) could augment inflammation by metabolic reprogramming.

Post-Cardiac Arrest Syndrome Is Not Associated With an Early Bacterial Translocation.

BACKGROUND: The aim of this study was to investigate bacterial translocation and its possible role in the development of post-resuscitation inflammatory response following Cardio-Pulmonary Resuscitation (CPR) after cardiac arrest. METHODS: Munich female swine were employed for a model of cardiac arrest via application of electrical current. After 7 min, CPR was initiated, and animals were either successfully return to spontaneous circulation (ROSC) within 40 min or not (no-ROSC). At the end of experimental period and prior to sacrifice, samples from the intestine, mesenteric lymph nodes (MLN), liver and portal vein blood were obtained. Evaluation of inflammation and gut permeability was performed; MLN, liver and portal vein samples were analyzed for 16 s rRNA detection and cytokine mRNA expression. RESULTS: A decreased expression of the tight junction protein Occludin, with higher levels of inflammation, greater epithelial disintegration, ulceration, loss of crypts and villi height were found in the intestines of the ROSC swine in comparison to no-ROSC. The macrophage surface antigen CD-14 staining was relatively more intense in the ROSC than in no-ROSC. Higher levels of TNF-α mRNA expression were present in the liver of the ROSC group. Finally, despite the inflammatory response and the gut mucosal alterations in ROSC group, no bacterial translocation was detected in liver, MLN and portal vein. CONCLUSIONS: We show that resuscitation from cardiac arrest induces inflammatory response and intestinal permeability in swine 4h after resuscitation, but not a bacterial translocation. Bacterial translocation is not an early phase phenomenon but probably part of the pathophysiologic sequelae.

Molecular Interactions between Erythrocytes and the Endocrine System.

Hormones are secreted by the endocrine glands and reach their targets after circulating in the blood. Many studies have documented that erythrocytes can bind hormones, and possible interactions have been reported. Erythrocytes are responsive to signaling initiated after binding of epinephrine, norepinephrine, estrogen, progesterone, thyroid hormones, parathyroid hormone, and angiotensin. Signaling results in regulation of cellular metabolism and membrane fluidity. In addition, erythrocytes are circulating pools for dopamine, thyroid hormones, cortisol, and aldosterone. Erythrocyte function and structure are regulated by endocrine signals, while erythrocytes are important constituents for the transport of hormones in the body.

Lipotoxicity Disrupts Erythrocyte Function: A Perspective.

BACKGROUND: Lipid accumulation in the liver, skeletal and cardiac muscle, kidneys and pancreas causes cell dysfunction, death and inflammation, a biological phenomenon named lipotoxicity. Erythrocytes participate in the transport of lipids in the circulation, and their lipidome is determined by exchange with blood components. OBJECTIVE: The objective of this study is to summarize the current knowledge regarding the effect of toxic lipid accumulation in erythrocytes. RESULTS: Erythrocyte lipidome is altered in lipotoxic diseases, such as fatty liver disease, heart failure and diabetes. In addition, ceramide, lysophosphatidylcholine, lysophosphatidic acid, palmitic acid and free cholesterol induce erythrocyte malfunction. CONCLUSION: Erythrocytes are an additional cell target of lipotoxicity. Further exploration of the implicated molecular mechanisms could lead to novel therapeutic targets for cardiometabolic and hematological diseases.

Immune and Metabolic Interactions of Human Erythrocytes: A Molecular Perspective.

Apart from their main function as oxygen carriers in vertebrates, erythrocytes are also involved in immune regulation. By circulating throughout the body, the erythrocytes are exposed and interact with tissues that are damaged as a result of a disease. In this study, we summarize the literature regarding the contribution of erythrocytes to immune regulation and metabolism. Under the circumstances of a disease state, the erythrocytes may lose their antioxidant capacity and release Damage Associated Molecular Patterns, resulting in the regulation of innate and adaptive immunity. In addition, the erythrocytes scavenge and affect the levels of chemokines, circulating cell-free mtDNA, and C3b attached immune complexes. Furthermore, through surface molecules, erythrocytes control the function of T lymphocytes, macrophages, and dendritic cells. Through an array of enzymes, red blood cells contribute to the pool of blood's bioactive lipids. Finally, the erythrocytes contribute to reverse cholesterol transport through various mechanisms. Our study is highlighting overlooked molecular interactions between erythrocytes and immunity and metabolism, which could lead to the discovery of potent therapeutic targets for immunometabolic diseases.

Cholesterol and Phospholipid Distribution Pattern in the Erythrocyte Membrane of Patients with Hepatitis C and Severe Fibrosis, before and after Treatment with Direct Antiviral Agents: A pilot Study.

Objectives: Hepatitis C virus requires and induces changes in liver lipidome for its life cycle. In addition, alterations in plasma and erythrocyte lipidome are observed during a range of chronic liver diseases. Methods: A total of six subjects (three males and three females) were included in our study. All subjects were HCV positive according to virus RNA detection. Erythrocyte ghosts were prepared from blood and collected upon diagnosis and also at the end of the treatment with Direct Antiviral Agents (DAA). Lipids were extracted from the erythrocyte ghosts, and cholesterol and phospholipids were analyzed by thin layer chromatography. A semi-quantitative estimation of cholesterol (CHOL), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylcholine (PC) and sphingomyelin (SM) was performed by densitometric analysis of the chromatographs. Results: After the antiviral treatment, PE percentage decreased, whereas the PC/PE and CHOL/PE ratio increased significantly. There were also other weaker differences for CHOL, PI, PS, PC and SM. Before DAA there was a very weak correlation between ALT and PC/PE ratio. In contrast, there was a steep negative correlation between these two parameters after DAA. Conclusion: Red blood cell lipid composition and especially the PC/PE ratio could be a candidate real time biological marker for inflammation resolution during hepatitis C treatment.

Red Blood Cell Dysfunction in Non-Alcoholic Fatty Liver Disease: Marker and Mediator of Molecular Mechanisms.

Despite efforts to unravel the pathogenetic mechanisms of non-alcoholic fatty liver disease (NAFLD), there is still a need for approved treatments and biomarkers. Interestingly, red blood cells present alterations in their characteristics during NAFLD. The phosphatidylcholine to phosphatidylethanolamine ratio, fatty acid profile, red blood cell count and red cell distribution width reflect molecular changes that are taking place in the liver. In addition, glycosylated hemoglobin, chemokine binding and release, and phosphatidylserine exposure actively participate in NAFLD pathogenesis. In this review, we describe the neglected red blood cell dysfunction in NAFLD, with the aim to unveil potent biomarkers and therapeutic targets.

Complications and problems related to pedicle screw fixation of the spine.

This retrospective study analyzes the complications and the problems developed during and after pedicle screw fixation in patients with spinal disorders and trauma. One hundred twelve patients were treated using the Cotrel-Dubousset pedicle screw fixation system for degenerative disease (57 patients), trauma (42 patients), infection (eight patients), and tumor (five patients) of the lumbar or thoracolumbar spine. The average age of the patients was 47 years and the average followup was 35 months. Forty-seven general complications were seen in 41 patients (36.5%). In addition, hardware failures were observed in 12 patients (10.7%), junctional problems were seen in five patients (4.5%), problems in the instrumented segments were seen in 39 patients (34.7%), and problems of balance occurred in five patients (4.5%). Although the rate of the reported complications was high, the final outcome of the patients was not affected significantly. Placement of the pedicle screws in the thoracolumbar and lumbar spine is a technically demanding procedure. It should be used by experienced and qualified surgeons who are aware of the pitfalls associated with its use.

Serratia spondylodiscitis after elective lumbar spine surgery: a report of two cases.

STUDY DESIGN: This report describes two cases of acute spondylodiscitis, caused by, complicating two different conditions: microdiscectomy for herniated nucleus pulposus and decompressing laminotomy for spinal stenosis. OBJECTIVE: To describe a rare and life-threatening spinal infection and discuss its successful management. SUMMARY OF BACKGROUND DATA: To our knowledge, no published reports in the English language have described this potentially devastating infection as a complication of elective noninstrumented discectomy or decompressive laminotomy. METHODS: Two cases of a very early onset of acute spondylodiscitis, caused by, after minimally invasive lumbar spine surgeries are presented. The elapsed time between these two complications was 1 week. The clinical presentation was characteristically stormy in both cases. On postoperative day 2, the patients developed high fever with intense chills and concomitant acute low back pain rapidly increasing in severity. The overall clinical appearance was alarming. The patients were carefully investigated immediately and scrutinized for possible origin of the infection. Treatment consisted of prompt intravenous antibiotics and surgical debridement. RESULTS: The history and clinical manifestations of postoperative spondylodiscitis were corroborated with magnetic resonance imaging findings and bacteriologic and hematologic laboratory examination. Blood cultures revealed as the responsible pathogenic microorganism. The source of the pathogens was contaminated normal saline used for surgical lavage. Both patients were able to completely resume their previous occupations after aggressive surgical debridement/irrigation and 3 months of antibiotic treatment. CONCLUSIONS: may become a potential pathogen, causing severe spinal infection after elective surgery. For prompt diagnosis and effective treatment of this life-threatening infection, one should maintain high index of suspicion and should not procrastinate in initiating treatment, which should consist of appropriate intravenous antibiotics and surgical debridement.