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

The Role of Mesenchymal Stem Cells and Imatinib in the Process of Liver Fibrosis Healing Through CCL2-CCR2 and CX3CL1-CX3CR1 Axes

Background

Persistent liver damage contributes to the development of liver fibrosis, marked by an accumulation of extracellular matrix. Macrophages play a pivotal role in this process, with the CCL2-CCR2 and CX3CR1-CX3CL1 axes serving as key regulators of macrophage recruitment, liver infiltration, and differentiation. In this study, utilizing a rat model of carbon tetrachloride (CCL4)-induced liver fibrosis, we aimed to investigate the impact of imatinib and bone marrow-derived mesenchymal stem cells (BM-MSCs) on the expression of these axis.

Methods

Sixteen Sprague-Dawley rats were divided into four groups: healthy, liver fibrosis, imatinib-recipient, and BM-MSC-recipient. Treatment effects were evaluated using histopathology and Sirus-red staining. Quantitative real-time PCR was employed to analyze changes in the expression of the genes CCL2, CCR2, CX3CL1, and CX3CR1.

Results

Histopathological assessments revealed the efficacy of imatinib and BM-MSCs in mitigating liver fibrosis. Our findings demonstrated a significant reduction in CCL2 and CCR2 expression in both imatinib and BM-MSCs treatment groups compared to the liver fibrosis group. Conversely, the gene expression of CX3CL1 and CX3CR1 increased in both therapeutic groups compared to the liver fibrosis groups.

Conclusions

The notable decrease in CCL2-CCR2 genes in both therapeutic groups suggests that BM-MSCs and imatinib may contribute to a decline in inflammatory macrophages within the liver. The lower CCL2-CCR2 expression in imatinib-recipient rats indicates better efficacy in modulating the recruitment of inflammatory macrophages. The elevated expression of CX3CL1 in BM-MSC-recipient rats suggests a greater impact on the polarization of LY6Chigh (inflammatory) to LY6Clow (anti-inflammatory) macrophages, warranting further investigation.

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.

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.