CXCL12 Limits Inflammation by Localizing Mononuclear Infiltrates to the Perivascular Space during Experimental Autoimmune Encephalomyelitis

Abstract

The inflammatory response in the CNS begins with the movement of leukocytes across the blood-brain barrier in a multistep process that requires cells to pass through a perivascular space before entering the parenchyma. The molecular mechanisms that orchestrate this movement are not known. The chemokine CXCL12 is highly expressed throughout the CNS by microendothelial cells under normal conditions, suggesting it might play a role maintaining the blood-brain barrier. We tested this hypothesis in the setting of experimental autoimmune encephalomyelitis (EAE) by using AMD3100, a specific antagonist of the CXCL12 receptor CXCR4. We demonstrate that the loss of CXCR4 activation enhances the migration of infiltrating leukocytes into the CNS parenchyma. CXCL12 is expressed at the basolateral surface of CNS endothelial cells in normal spinal cord and at the onset of EAE. This polarity is lost in vessels associated with an extensive parenchymal invasion of mononuclear cells during the peak of disease. Inhibition of CXCR4 activation during the induction of EAE leads to loss of the typical intense perivascular cuffs, which are replaced with widespread white matter infiltration of mononuclear cells, worsening the clinical severity of the disease and increasing inflammation. Taken together, these data suggest a novel anti-inflammatory role for CXCL12 during EAE in that it functions to localize CXCR4-expressing mononuclear cells to the perivascular space, thereby limiting the parenchymal infiltration of autoreactive effector cells.

CXCR4 promotes differentiation of oligodendrocyte progenitors and remyelination

“…Sources of CXCL12 in the normal adult CNS include neurons, endothelial cells, and meninges (13,15,25), whereas astrocyte expression of CXCL12 has been observed only in several pathological states including MS, HIV-1 encephalitis, and malignancy (29,(31)(32)(33). In studies of MS tissues, CXCL12 expression is observed within activated astrocytes in both silent and active MS lesions (34), suggesting its expression occurs in response to injury.…”

“…Frozen sections were prepared as described (25). Detection of CXCL12, GFAP, CD11b, NG2, MBP, BrDU, and CXCR4 antibodies were all assayed as described (25).…”

“…Total RNA and quantitative real-time (qRT)-PCR was performed using primers generated using Primer Express 2.0 software (Applied Biosystems) for CXCL12 and CXCR4 as published previously (25).…”

“…AMD 3100, which has a plasma half-life of 0.9 h in rodents after i.p. injection (24), was continually dosed via the s.c. implantation of drug-infused osmotic pumps, as previously described (25). Continuous administration of AMD3100 for 2 wk, begun after 6 wk of CPZ ingestion, at the time of refeeding with normal chow, led to increased numbers of CXCR4+NG2+ cells within the CC compared with mice that received vehicle (PBS) alone (Fig.…”

Chemokines and Chemokine Receptors in Neurological Disease: Raise, Retain, or Reduce?

“…83 Studies using AMD3100 have also been conducted in the EAE model. 84 Animals treated with this CXCR4 antagonist displayed worsened clinical disease and extensive demyelination, although numbers of mononuclear cells were similar in CNS tissues and in vehicle-treated mice. The AMD3100-treated mice, however, showed an increase in microglial activation and remarkably dispersed intraparenchymal lymphocyte infiltrates.…”