Effects Of CCL2 Research Articles

RETRACTED ARTICLE: Long non-coding RNA CCL2 promoted gastric cancer function via miR-128/ PARP2 signal pathway

Statement of Retraction Liang Ma, Yunshan Jiang, Ning Wu. 2022. Long non-coding RNA CCL2 promoted gastric cancer function via miR-128/ PARP2 signal pathway - 2022, Long non-coding RNA CCL2 promoted gastric cancer function via miR-128/ PARP2 signal pathway, Bioengineered 13(1), doi: 10.1080/21655979.2021.2020548 Since publication, significant concerns have been raised about the integrity of the data and reported results in the article. When approached for an explanation, the authors did not provide their original data or any necessary supporting information. As verifying the validity of published work is core to the integrity of the scholarly record, we are therefore retracting the article. All authors listed in this publication have been informed. We have been informed in our decision-making by our editorial policies and the COPE guidelines. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Neuronal CCL2 is upregulated during hepatic encephalopathy and contributes to microglia activation and neurological decline.

BackgroundAcute liver failure leads to systemic complications with one of the most dangerous being a decline in neurological function, termed hepatic encephalopathy. Neurological dysfunction is exacerbated by an increase of toxic metabolites in the brain that lead to neuroinflammation. Following various liver diseases, hepatic and circulating chemokines, such as chemokine ligand 2 (CCL2), are elevated, though their effects on the brain following acute liver injury and subsequent hepatic encephalopathy are unknown. CCL2 is known to activate microglia in other neuropathies, leading to a proinflammatory response. However, the effects of CCL2 on microglia activation and the pathogenesis of hepatic encephalopathy following acute liver injury remain to be determined.MethodsHepatic encephalopathy was induced in mice via injection of azoxymethane (AOM) in the presence or absence of INCB 3284 dimesylate (INCB), a chemokine receptor 2 inhibitor, or C 021 dihydrochloride (C021), a chemokine receptor 4 inhibitor. Mice were monitored for neurological decline and time to coma (loss of all reflexes) was recorded. Tissue was collected at coma and used for real-time PCR, immunoblots, ELISA, or immunostaining analyses to assess the activation of microglia and consequences on pro-inflammatory cytokine expression.ResultsFollowing AOM administration, microglia activation was significantly increased in AOM-treated mice compared to controls. Concentrations of CCL2 in the liver, serum, and cortex were significantly elevated in AOM-treated mice compared to controls. Systemic administration of INCB or C021 reduced liver damage as assessed by serum liver enzyme biochemistry. Administration of INCB or C021 significantly improved the neurological outcomes of AOM-treated mice, reduced microglia activation, reduced phosphorylation of ERK1/2, and alleviated AOM-induced cytokine upregulation.ConclusionsThese findings suggest that CCL2 is elevated systemically following acute liver injury and that CCL2 is involved in both the microglia activation and neurological decline associated with hepatic encephalopathy. Methods used to modulate CCL2 levels and/or reduce CCR2/CCR4 activity may be potential therapeutic targets for the management of hepatic encephalopathy due to acute liver injury.

CCL2-ethanol interactions and hippocampal synaptic protein expression in a transgenic mouse model.

Chronic exposure to ethanol produces a number of detrimental effects on behavior. Neuroadaptive changes in brain structure or function underlie these behavioral effects and may be transient or persistent in nature. Central to the functional changes are alterations in the biology of neuronal and glial cells of the brain. Recent data show that ethanol induces glial cells of the brain to produce elevated levels of neuroimmune factors including CCL2, a key innate immune chemokine. Depending on the conditions of ethanol exposure, the upregulated levels of CCL2 can be transient or persistent and outlast the period of ethanol exposure. Importantly, results indicate that the upregulated levels of CCL2 may lead to CCL2-ethanol interactions that mediate or regulate the effects of ethanol on the brain. Glial cells are in close association with neurons and regulate many neuronal functions. Therefore, effects of ethanol on glial cells may underlie some of the effects of ethanol on neurons. To investigate this possibility, we are studying effects of chronic ethanol on hippocampal synaptic function in a transgenic mouse model that expresses elevated levels of CCL2 in the brain through enhanced glial expression, a situation know to occur in alcoholics. Both CCL2 and ethanol have been reported to alter synaptic function in the hippocampus. In the current study, we determined if interactions are evident between CCL2 and ethanol at the level of hippocampal synaptic proteins. Two ethanol exposure paradigms were used; the first involved ethanol exposure by drinking and the second involved ethanol exposure in a paradigm that combines drinking plus ethanol vapor. The first paradigm does not produce dependence on ethanol, whereas the second paradigm is commonly used to produce ethanol dependence. Results show modest effects of both ethanol exposure paradigms on the level of synaptic proteins in the hippocampus of CCL2 transgenic mice compared with their non-transgenic littermate controls, consistent with ethanol-CCL2 interactions. No evidence of toxic effects of CCL2 or CCL2-ethanol interactions was observed. Taken together, these results support the idea that ethanol induced astrocyte production of CCL2 can result in neuroadaptive changes that interact with the actions of ethanol.

CCL2 disrupts the adherens junction: implications for neuroinflammation

Alterations to blood–brain barrier (BBB) adhesion molecules and junctional integrity during neuroinflammation can promote central nervous system (CNS) pathology. The chemokine CCL2 is elevated during CNS inflammation and is associated with endothelial dysfunction. The effects of CCL2 on endothelial adherens junctions (AJs) have not been defined. We demonstrate that CCL2 transiently induces Src-dependent disruption of human brain microvascular endothelial AJ. β-Catenin is phosphorylated and traffics from the AJ to PECAM-1 (platelet endothelial cell adhesion molecule-1), where it is sequestered at the membrane. PECAM-1 is also tyrosine-phosphorylated, an event associated with recruitment of the phosphatase SHP-2 (Src homology 2 domain-containing protein phosphatase) to PECAM-1, β-catenin release from PECAM-1, and reassociation of β-catenin with the AJ. Surface localization of PECAM-1 is increased in response to CCL2. This may enable the endothelium to sustain CCL2-induced alterations in AJ and facilitate recruitment of leukocytes into the CNS. Our novel findings provide a mechanism for CCL2-mediated disruption of endothelial junctions that may contribute to BBB dysfunction and increased leukocyte recruitment in neuroinflammatory diseases.

Adiponectin stimulates release of CCL2, -3, -4 and -5 while the surface abundance of CCR2 and -5 is simultaneously reduced in primary human monocytes

The adipokine adiponectin is well known to affect the function of immune cells and upregulation of CCL2 by adiponectin in monocytes/macrophages has already been reported. In the current study the effect of adiponectin on CCL2, -3, -4, and -5 and their corresponding receptors CCR1, CCR2, and CCR5 has been analyzed. Adiponectin elevates mRNA and protein of the CC chemokines in primary human monocytes. Simultaneously the surface abundance of CCR2 and CCR5 is reduced while CCR1 is not affected. Downregulation of CCR2 by adiponectin is blocked by a CCR2 antagonist although expression of the CCL2 regulated genes CCR2 and TGF-beta 1 is not altered in the adiponectin-incubated monocytes. CCL2, -3, and -5 concentrations measured in supernatants of monocytes of normal-weight (NW), overweight (OW), and type 2 diabetic (T2D) patients positively correlate with BMI and are increased in obesity and T2D. In contrast CCL4 is similarly abundant in the supernatants of all of these monocytes. The degree of adiponectin-mediated induction of the chemokines CCL3, -4, and -5 negatively correlates with their basal levels and upregulation of CCL3 and CCL5 is significantly impaired in OW and T2D cells. Serum concentrations of these chemokines are almost equal in the three groups and do not correlate with the levels in monocyte supernatants. In conclusion these data demonstrate that adiponectin stimulates release of CCL2 to CCL5 in primary human monocytes, and induction in cells of overweight probands is partly impaired. Adiponectin also lowers surface abundance of CCR2 and CCR5 and downregulation of CCR2 seems to depend on autocrine/paracrine effects of CCL2.

Effect of CCL2 on survival of breast cancer MDA-MB-231 cells via inhibition of apoptosis

e22176 Background: The cytokine CCL2 (Chemokine (C-C) motif ligand 2 or monocyte chemo attractant protein-1 MCP-1) has been shown to play an important role in breast cancer progression by promoting angiogenesis and migration. CCL2 is over-expressed by breast cancer cells as well as by macrophages and mesenchymal stem cells in the tumor micro-environment. We studied the effects of CCL2 and IL-6 on survival of breast cancer MDA-MB-231 cells. Methods: Cytokine expression including of CCL2 and IL- 6 were analyzed in supernatants from MDA-MB-231 cells using cytokine antibody array (Human Antibody Array 3; Ray Biotech, Inc). Serum starved MDA-MB-231 cells were treated with CCL2 (75 ng/mL) and IL-6 (100 ng/mL; both from Apollo Cytokine Research). Cell viability in response to treatment was analyzed at serial time points by cell proliferation assay WST-1 (Roche Applied Science). Protein expression of genes of interest was studied by Western blot. Results: In contrast to primary breast tumor cells, MDA-MB-231 cells express minimal CCL2 at baseline. MDA-MB-231 cells also exhibit low expression of IL-6. Stimulation of MDA-MB-231 cells with either exogenous CCL2 or exogenous IL-6 did not increase levels of the other cytokine. In MDA-MB-231 cells, CCL2, alone and in combination with IL-6, promotes survival in serum starved conditions. Treatment of MDA-MB-231 cells with CCL2 leads to survivin up-regulation beginning at 48 hours as determined by immunoblotting analysis. CCL2 in combination with IL-6 inhibits the cleavage of PARP, lamin and caspase3. Conclusions: There is minimal endogenous expression of CCL2 in MDA-MB-231 cells. CCL2 from the tumor micro-environment promotes survival of MDA-MB-231 cells associated with up-regulation of survivin. IL-6 may play a syngeristic role with CCL2 in promoting survival of MDA-MB-231 cells. We plan to explore the role of survivin up-regulation in protecting cells from cell death. Our findings raise the possibility of utilizing neutralizing antibodies against CCL2 in therapy of breast cancer. No significant financial relationships to disclose.

Protein Kinase Cα-RhoA Cross-talk in CCL2-induced Alterations in Brain Endothelial Permeability

Monocyte chemoattractant protein-1 (MCP-1 or CCL2) regulates blood-brain barrier permeability by inducing morphological and biochemical alterations in the tight junction (TJ) complex between brain endothelial cells. The present study used cultured brain endothelial cells to examine the signaling networks involved in the redistribution of TJ proteins (occludin, ZO-1, ZO-2, claudin-5) by CCL2. The CCL2-induced alterations in the brain endothelial barrier were associated with de novo Ser/Thr phosphorylation of occludin, ZO-1, ZO-2, and claudin-5. The phosphorylated TJ proteins were redistributed/localized in Triton X-100-soluble as well as Triton X-100-insoluble cell fractions. Two protein kinase C (PKC) isoforms, PKCalpha and PKCzeta, had a significant impact on this event. Inhibition of their activity using dominant negative mutants PKCalpha-DN and PKCzeta-DN diminished CCL2 effects on brain endothelial permeability. Previous data indicate that Rho/Rho kinase signaling is involved in CCL2 regulation of brain endothelial permeability. The interactions between the PKC and Rho/Rho kinase pathways were therefore examined. Rho, PKCalpha, and PKCzeta activities were knocked down using dominant negative mutants (T17Rho, PKCalpha-DN, and PKCzeta-DN, respectively). PKCalpha and Rho, but not PKCzeta and Rho, interacted at the level of Rho, with PKCalpha being a downstream target for Rho. Double transfection experiments using dominant negative mutants confirmed that this interaction is critical for CCL2-induced redistribution of TJ proteins. Collectively these data suggest for the first time that CCL2 induces brain endothelial hyperpermeability via Rho/PKCalpha signal pathway interactions.