Monocyte chemoattractant protein-1 is a pathogenic component in a model for a hereditary peripheral neuropathy

Macrophages are critically involved in the pathogenesis of genetically caused demyelination, as it occurs in models for inherited demyelinating neuropathies. It is presently unknown which factors link the Schwann cell-based myelin mutation to the activation of endoneurial macrophages. Here we identified the chemokine monocyte chemoattractant protein-1 (MCP-1) as a first and crucial factor upregulated in Schwann cells of mice heterozygously deficient for the myelin protein zero. The chemokine could be identified as an important mediator of macrophage immigration into peripheral nerves. Furthermore, a 50% reduction of chemokine expression by crossbreeding with MCP-1-deficient mice reduced the increase in macrophage numbers in the mutant nerves and lead to a robust amelioration of pathology. Surprisingly, the complete absence of MCP-1 aggravated the disease. Our findings show that reducing but not eliminating chemokine expression can rescue genetically caused demyelination that may be an interesting target in treating demyelinating diseases of the peripheral nervous system.     

Monocyte chemoattractant protein-1 regulation of blood-brain barrier permeability.

The present study was designed to elucidate the effects of the chemokine monocyte chemoattractant protein (MCP-1) on blood-brain barrier (BBB) permeability. Experiments were conducted under in vitro conditions (coculture of brain endothelial cells and astrocytes) to study the cellular effects of MCP-1 and under in vivo conditions (intracerebral and intracerebroventricular administration of MCP-1) to study the potential contribution of MCP-1 to BBB disruption in vivo. Our results showed that MCP-1 induces a significant increase in the BBB permeability surface area product for fluorescein isothiocyanate (FITC)-albumin under in vivo conditions, particularly during prolonged (3 or 7 days) exposure (0.096+/-0.008 versus 0.031+/-0.005 microL/g min in controls at 3 days, P<0.001). Monocyte chemoattractant protein-1 also enhanced (17-fold compared with control) the permeability of the in vitro BBB (coculture) model. At the cellular level, MCP-1 causes alteration of tight junction (TJ) proteins in endothelial cells (redistribution of TJ proteins determined by Western blotting and loss of immunostaining for occludin, claudin-5, ZO-1, ZO-2). Monocyte chemoattractant protein-1-induced alterations in BBB permeability are mostly realized through the CCR2 receptor. Absence of CCR2 diminishes any effect of MCP-1 on BBB permeability in vitro and in vivo. The permeability surface area product for FITC-albumin after 3 days exposure to MCP-1 was 0.096+/-0.006 and 0.032+/-0.007 microL/g min, in CCR2+/+ and CCR2-/- mice, respectively (P<0.001). Monocytes/macrophages also participate in MCP-1-induced alterations in BBB permeability in vivo. Monocytes/macrophages depletion (by clodronate liposomes) reduced the effect of MCP-1 on BBB permeability in vivo approximately 2 fold. Our results suggest that, besides its main function of recruiting leukocytes at sites of inflammation, MCP-1 also plays a role in 'opening' the BBB.     

Monocyte chemoattractant protein-1 plays a critical role in neuroblast migration after focal cerebral ischemia.

Transient focal ischemia is known to induce proliferation of neural progenitors in adult rodent brain. We presently report that doublecortin positive neuroblasts formed in the subventricular zone (SVZ) and the posterior peri-ventricle region migrate towards the cortical and striatal penumbra after transient middle cerebral artery occlusion (MCAO) in adult rodents. Cultured neural progenitor cells grafted into the non-infarcted area of the ipsilateral cortex migrated preferentially towards the infarct. As chemokines are known to induce cell migration, we investigated if monocyte chemoattractant protein-1 (MCP-1) has a role in post-ischemic neuroblast migration. Transient MCAO induced an increased expression of MCP-1 mRNA in the ipsilateral cortex and striatum. Immunostaining showed that the expression of MCP-1 was localized in the activated microglia and astrocytes present in the ischemic areas between days 1 and 3 of reperfusion. Furthermore, infusion of MCP-1 into the normal striatum induced neuroblast migration to the infusion site. The migrating neuroblasts expressed the MCP-1 receptor CCR2. In knockout mice that lacked either MCP-1 or its receptor CCR2, there was a significant decrease in the number of migrating neuroblasts from the ipsilateral SVZ to the ischemic striatum. These results show that MCP-1 is one of the factors that attract the migration of newly formed neuroblasts from neurogenic regions to the damaged regions of brain after focal ischemia.     

Monocyte chemoattractant protein-1 correlates with subcortical brain injury in HIV infection

Various biomarkers have been suggested as associative or predictive of HIV-associated neurocognitive impairment. Plasma levels of monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor alpha (TNF-alpha), and hematocrit were evaluated for relationships with diffusion tensor imaging measurements of centrum semiovale, caudate, and putamen. MCP-1 levels correlated with tissue status (mean diffusivity) in all examined regions. Plasma markers were also significantly correlated with anisotropy measurements in centrum semiovale (TNF-alpha) and putamen (hematocrit).     

Monocyte chemoattractant protein-1 increases microglial infiltration and aggressiveness of gliomas

Macrophages are thought to represent a first line of defense in anti-tumor immunity. Despite infiltration by microglial cells, however, malignant gliomas are still highly aggressive tumors. We here identify monocyte chemoattractant protein-1 (MCP-1) as a critical chemoattractant for glioma-infiltrating microglial cells. MCP-1-transfected rat CNS-1 gliomas were massively infiltrated by microglial cells. Whereas MCP-1 did not promote the growth of CNS-1 cells in vitro, intracerebral CNS-1-transfected tumors grew more aggressively than control-transfected tumors. This provides the first functional evidence that MCP-1 recruits microglial cells to gliomas and promotes their growth in vivo. Microglial cells may support rather than suppress glioma growth.     

Monocyte chemoattractant protein-1 immunoreactivity in sensory ganglia and hindpaw after adjuvant injection

Monocyte chemoattractant protein-1 (MCP-1)/CCL2 is a member of the CC chemokine family that exhibits potent chemotactic activity for monocytes/macrophages. In the current study, the proportion of monocyte chemoattractant protein-1-immunoreactive (IR) neurons in the dorsal root ganglion (DRG) of rats was shown to increase markedly following adjuvant injection into the hindpaw. MCP-1-IR axon terminals were not found in the spinal cord or hindpaw of control or adjuvant-treated rats. Instead, the inflamed hindpaw dermis was infiltrated by numerous MCP-1-IR inflammatory cells. Following adjuvant injection, the majority of MCP-1-IR neurons in the DRG colocalized with IB4 binding. Our findings suggest that peripheral tissue inflammation induces increased MCP-1 expression in DRG neurons and this may be dependent upon glial cell line-derived neurotrophic factor.     

Monocyte chemoattractant protein-1 expressed in neurons and astrocytes during focal ischemia in mice

Focal cerebral ischemia elicits an inflammatory response characterized by the infiltration and accumulation of leukocytes, as well as the secretion of inflammatory mediators (Clark et al., Brain Res. Bull., 35 (1994) 387-392; Garcia et al., Am. J. Pathol., 144 (1994) 188-199; Wang et al., J. Neurochem. 71 (1998) 1194-1204). Leukocytes eliminate microbial invaders and necrotizing tissue debris, and can also turn against surrounding healthy tissue and exacerbate tissue injury (Furie and Randolph, Am. J. Pathol., 146 (1995) 1287-1301; Kochanek and Hallenbeck, Stroke 23 (1992) 1367-1379). Inflammatory mediators are considered to play an important role in attracting and stimulating leukocytes (Weiss, N. Engl. J. Med., 320 (1989) 365-376). Monocyte chemoattractant protein-1 (MCP-1) functions as an inflammatory mediator, whose source and role in focal cerebral ischemia is worth studying. MCP-1, a potent chemoattractant factor, may play an important role in ischemia-induced inflammatory response. The aim of the present study is to determine the time course and cell type of MCP-1 protein expression after permanent focal ischemia in mice. ELISA and immunohistochemical staining were used to detect the expression of MCP-1 protein after 0 h, 2 h, 4 h, 12 h, 1 day, 2 days, 3 days, 5 days and 7 days of middle cerebral artery occlusion (n=3-5 in each group). Double-labeled fluorescent staining was used to examine the cellular localization of MCP-1. The results demonstrated that MCP-1 expression was mainly observed in the ischemic core after 12 h of middle cerebral artery occlusion, then gradually increased and extended to the ischemic perifocal area. MCP-1 expression peaked at 2 days and 3 days, and gradually decreased after 5 days of MCAO. Double-labeled immunostaining for MCP-1 and neuron specific enolase (NSE) or glial fibrillary acidic protein (GFAP) showed that MCP-1 positive neurons were observed as early as 12 h of ischemia, while MCP-1 positive astrocytes were observed after 2 days of ischemia. These results support the functional role of MCP-1 in ischemic brain injury and reveal a distinct temporal and spatial expression of MCP-1 in cells believed to be neurons and astrocytes.     

Monocyte chemoattractant protein-1 (MCP1) promoter -2518 polymorphism may confer a susceptibility to major depressive disorder in the Korean population

We conducted a case-control association study of the monocyte chemoattractant protein-1 (MCP1) gene -2518 polymorphism in 90 patients with major depressive disorder. Genotyping was performed by polymerase chain reaction methods. We found significant differences in genotype and allele frequencies. The present study suggests that this polymorphism may confer a susceptibility to major depressive disorder in the Korean population.     

Monocyte chemoattractant protein 1 is responsible for macrophage recruitment following injury to sciatic nerve

Following injury to the peripheral nervous system, circulating monocytes/macrophages are recruited to the damaged tissue, where they play vital roles during both nerve degeneration and subsequent regeneration. Monocyte chemoattractant protein-1 (MCP-1), a member of the C-C or β-chemokine family, is a powerful leukocyte recruitment/activation factor that is relatively specific for monocytes/macrophages. Because these are the predominant leukocyte type recruited by injured nerve, we hypothesized that up-regulation of MCP-1 expression is involved in recruitment of these cells. Indeed, assay of steady-state levels of MCP-1 mRNA in rat sciatic nerve during tellurium-induced primary demyelination indicated up-regulation of this chemokine with a peak after 3 days of tellurium exposure, preceding the peak of accumulation of phagocytic macrophages (assayed as lysozyme mRNA levels) by 6 days. Increasing levels of MCP-1 mRNA expression, induced by increasing levels of tellurium exposure, resulted in corresponding increases in subsequent recruitment of macrophages. In situ hybridization suggested that MCP-1 mRNA was localized in Schwann cells. No expression of MIP-2, which is a C-X-C or α-chemokine that is specific for recruitment of neutrophils, was detected, consistent with the lack of recruitment of significant numbers of these cells. In addition, we also investigated the response seen following nerve transection (axonal degeneration and secondary demyelination with no subsequent regeneration) and nerve crush (degeneration followed by regeneration). In these latter two nerve injury models, there was also a marked, early up-regulation of MCP-1 mRNA, with a time course that is compatible with a role for this chemokine in macrophage recruitment. We conclude that MCP-1 is involved in recruiting monocytes/macrophages to injured peripheral nerve and that the specificity of leukocyte types recruited results from specificity of chemokine production. J. Neurosci. Res. 53:260–267, 1998. © 1998 Wiley-Liss, Inc.     

Tumor necrosis factor is required for RANTES-induced astrocyte monocyte chemoattractant protein-1 production

Astrocytes respond to stimulation with the chemokine RANTES (regulated on activation, normal T cell expressed) by production of a series of cytokines and chemokines, including tumor necrosis factor-alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1). In the present study we demonstrate that RANTES induces TNF, which in turn stimulates subsequent production of MCP-1. TNF-R1 (p55) serves as the principal receptor responsible for MCP-1 synthesis. The results define an astrocyte proinflammatory cascade that amplifies synthesis of proinflammatory mediators. The implications of these findings to inflammatory diseases of the central nervous system are discussed.     

Production of monocyte chemoattractant protein-1 in amyotrophic lateral sclerosis

The presence of activated microglia in the spinal cord of amyotrophic lateral sclerosis (ALS) patients is usually accompanied by inflammatory biochemical changes, but these are largely unexplored. Monocyte chemoattractant protein-1 (MCP-1) is critical for recruitment of inflammatory cells of monocytic lineage after inflammation or injury to the central nervous system. MCP-1 concentrations were measured by an enzyme-linked immunosorbent assay in the cerebrospinal fluid (CSF) and the serum of 27 patients with ALS and 30 patients with noninflammatory neurological diseases. In ALS, circulating MCP-1 levels were significantly increased in the serum and particularly in the CSF. Immunoreactivity for MCP-1 in ALS spinal cord was detected mostly in astrocytes but also in microglia, neurons, and within the vasculature of the cord. Our findings suggest a role for MCP-1 as an important molecular mediator of the injury response in ALS.     

Monocyte chemoattractant protein-1 promoter -2518 polymorphism may have an influence on clinical heterogeneity of bipolar I disorder in the Korean population

The aim of this study was to investigate the association between monocyte chemoattractant protein-1 (MCP1) promoter -2518 polymorphism and DSM-IV-based bipolar I disorder (BID) in Korea. Ninety-two patients with BID and 114 healthy controls participated in this study. A polymerase chain reaction-based method was used for genotyping. Genotype and allele distributions in patients with BID were not different from those of the controls, nor were they different according to clinical factors in the patient group. However, the frequency of the A allele (p = 0.028) was significantly different when subdividing the patient group into patients with manic episode versus depressed and mixed episode. The present study suggests that the MCP1 promoter -2518 polymorphism may not confer susceptibility to BID itself, but could have an influence on the clinical heterogeneity of BID, at least in the Korean population.     

Monocyte chemoattractant protein (MCP)-1 is rapidly expressed by sympathetic ganglion neurons following axonal injury

EDI-immunoreactive macrophages, absent from the superior cervical ganglia (SCG) of normal rats, appear in these ganglia within 48h after postganglionic axotomy. Further, resident macrophages show changes after axotomy. Since chemokines function as chemoattractants and activators of leukocytes, the effects of axotomy on chemokine expression in the SCG were examined. Within 6 h after nerve transection, increases were seen in mRNA levels for monocyte chemoattractant protein (MCP)-1. MCP-1 mRNA was concentrated in a population of neurons, while MCP-1 protein was localized to endothelial cells. This axotomy-induced neuronal MCP-1 expression may trigger the infiltration and/or activation of macrophages in SCG after injury.     

Monocyte chemoattractant protein-1 (MCP-1) produced via NF-kappaB signaling pathway mediates migration of amoeboid microglia in the periventricular white matter in hypoxic neonatal rats

Monocyte chemoattractant protein-1 (MCP-1), a member of beta-chemokine subfamily, regulates the migration of microglia, monocytes, and lymphocytes to the inflammatory site in the central nervous system. We sought to determine if amoeboid microglial cells (AMC) produce MCP-1 that may be linked to migration of AMC in the corpus callosum periventricular white matter in hypoxic neonatal rats. A striking feature in 1-day-old rats subjected to hypoxia was a marked increase in cell numbers of AMC and immunoexpression of MCP-1 and its receptor (CCR(2)). By BrdU immunostaining, there was no significant change in the proliferation rate of AMC after hypoxic exposure when compared with the corresponding control rats. When injected intracerebrally into the corpus callosum of 7-day-old postnatal rats, MCP-1 induced the chemotactic migration of AMC to the injection site. In primary microglial cell culture subjected to hypoxia, there was a significant increase in MCP-1 release involving NF-kappaB signaling pathway. In in vitro chemotaxis assay, the medium derived from hypoxia-treated microglial cultures attracted more migratory microglial cells than that from the control microglial culture. The present results suggest that following a hypoxic insult, AMC in the neonatal rats increase MCP-1 production via NF-kappaB signaling pathway. This induces the migration and accumulation of AMC from the neighboring areas to the periventricular white matter (PWM). It is concluded that the preponderance and active migration of AMC, as well as them being the main cellular source of MCP-1, may offer an explanation for the PWM being susceptible to hypoxic damage in neonatal brain.     

Anti-monocyte chemoattractant protein-1 gene therapy protects against focal brain ischemia in hypertensive rats.

Monocyte chemoattractant protein-1 (MCP-1) is expressed in the ischemic cortex after focal brain ischemia and appears to exacerbate ischemic damage. The authors examined the effect of gene transfer of dominant negative MCP-1, called 7ND, 90 minutes after induction of focal brain ischemia in hypertensive rats. Adenoviral vectors encoding mutant MCP-1 (Ad7ND; n = 11), or Escherichia coli beta-galactosidase (AdlacZ; n = 17) as control were injected into the lateral ventricle of male spontaneously hypertensive rats. Both AdlacZ (n = 12) and Ad7ND (n = 6) administration provided transgene expression as early as 6 hours after injection and the expression further increased on day 1, followed by a sustained detection on day 5. Five days after ischemia, infarct volume (75 +/- 13 mm, n = 5, mean +/- SD) significantly reduced to 72% of control (104 +/- 22 mm3, n = 5, P < 0.05) by 7ND gene transfer. Numbers of leukocytes in the vessels (48.3 +/- 32.9/cm2) and macrophage/monocyte infiltration (475.2 +/- 125.5/mm2) of the infarct area in the Ad7ND group were significantly less than those measured in the AdlacZ group (143.8 +/- 72.1/cm2 and 671.8 +/- 125.5/mm2, P < 0.05, respectively). In summary, the postischemic gene transfer of dominant negative MCP-1 attenuated the infarct volume and infiltration of inflammatory cells, suggesting potential usefulness of the anti-MCP-1 gene therapy.     

Vascular adhesion protein-1 in human ischaemic stroke

Aims: Leukocyte extravasation exacerbates tissue injury after ischaemic stroke. Vascular adhesion protein-1 (VAP-1) is an endothelial adhesion molecule with the potential capacity to guide transmigration of inflammatory cells into ischaemic brain. Moreover, VAP-1 could worsen ischaemic brain injury due to its function as a semicarbazide-sensitive amine oxidase (SSAO) producing toxic metabolites from primary amines. The purpose of this study was to elucidate these aspects of VAP-1-function in the pathogenesis of human ischaemic stroke. Methods: We studied VAP-1 expression in infarcted and control brains post mortem using immunohistochemistry. Levels of soluble VAP-1 (sVAP-1) in the serum of patients with acute stroke and in control sera were determined using enzyme-linked immunosorbent assay. Results: In the acute phase of ischaemic stroke, the frequency of VAP-1-stained vessels was strongly diminished in the ipsilateral hemisphere but in the contralateral hemisphere it was comparable with the expression in the control brains. In the serum of acute stroke patients with a symptom duration <6 h the level of sVAP-1 was significantly increased (652 ± 224 ng/ml; mean ± SD) when compared with an age- and sex-matched control group (542 ± 104 ng/ml; P  < 0.05). Conclusions: As both cell surface and sVAP-1 possess vasculopathy-promoting SSAO enzymatic activity, our results imply that by inducing SSAO-derived toxic metabolites, VAP-1 might aggravate ischaemic vascular changes. The subsequent release of sVAP-1 into circulation could be further examined as a potential marker of early ischaemic vasculopathy.