A potential novel therapeutic target in diabetic retinopathy: a chemokine receptor (CCR2/CCR5) inhibitor reduces retinal vascular leakage in an animal model

PURPOSE

We have previously shown that the chemokine CCL2 plays an important role in monocyte trafficking into the retina and alteration of the BRB in an animal model of diabetic retinopathy. In this study, we examined the effect of pharmacologically targeting the chemokine pathway to reduce the increased retinal vascular permeability in this model.

METHODS

C57BL/6 J mice were made diabetic using streptozotocin. After 4 months of diabetes, mice (n = 10) were treated by intraperitoneal injections of TAK-779 (dual CCR2/CCR5 inhibitor) (30 mg/kg) daily for 2 weeks. Retinal vascular permeability and protein expression were done using western blot. The SDF-1 levels were measured by ELISA. Immune cell infiltration in the retinas was measured using flow cytometry.

RESULTS

The dual inhibitor significantly decreased retinal vascular permeability in diabetic animals. There was a significant reduction in macrophage/microglia infiltration in the retinas of treated animals. Levels of SDF-1 and ICAM-1 were significantly reduced and the tight junction protein ZO-1 level was increased, and phospho-VE-Cad was significantly reduced with drug treatment.

CONCLUSIONS

A chemokine receptor inhibitor (CCR2/CCR5) can reduce retinal vascular permeability in diabetic animals. Targeting the chemokine pathway pharmacologically may be used as a novel therapeutic strategy in management of diabetic macular edema.

ROCK is essential for directionally persistent migration of CD8+ effector T cells within inflamed lung

Recruitment of effector T lymphocytes into peripheral tissues, such as inflamed lung, contributes to an effective protection against infection and cancer. The rate of pathogen detection might be further influenced by the motility of recruited immune cells within three-dimensional tissues. Indeed, recent two-photon studies have shown that effector T cells navigate actively through inflamed lung tissue, but the molecular mechanisms that regulate this process are poorly characterized. Here, we used two-photon imaging of a murine lung treated with endotoxin to quantitatively analyze tissue navigation of lung-infiltrating CD8+ effector T cells. Tracking of individual T cells within inflamed lung tissue for several hours revealed that T cell movement transitions between periods of high directional persistence and confinement. Some T cells also moved in alignment with the vasculature. Treatment with pertussis toxin to inhibit chemokine receptor-dependent Gi-type G protein signaling led to a moderate reduction of the speed of lung-infiltrating T cells. Strikingly, pharmacological inhibition of the molecule ROCK, which promotes cytoskeleton-dependent squeezing through dense environments, led to a pronounced reduction of speed and almost completely abolished directional persistence of lung-infiltrating effector T cells. Together, these results show that migration of lung-infiltrating T cells is fine-tuned by environmental signals and dependent on the cell-intrinsic ROCK-signaling pathway.

Chemokine mediated monocyte trafficking into the retina: role of inflammation in alteration of the blood-retinal barrier in diabetic retinopathy

Inflammation in the diabetic retina is mediated by leukocyte adhesion to the retinal vasculature and alteration of the blood-retinal barrier (BRB). We investigated the role of chemokines in the alteration of the BRB in diabetes. Animals were made diabetic by streptozotocin injection and analyzed for gene expression and monocyte/macrophage infiltration. The expression of CCL2 (chemokine ligand 2) was significantly up-regulated in the retinas of rats with 4 and 8 weeks of diabetes and also in human retinal endothelial cells treated with high glucose and glucose flux. Additionally, diabetes or intraocular injection of recombinant CCL2 resulted in increased expression of the macrophage marker, F4/80. Cell culture impedance sensing studies showed that purified CCL2 was unable to alter the integrity of the human retinal endothelial cell barrier, whereas monocyte conditioned medium resulted in significant reduction in cell resistance, suggesting the relevance of CCL2 in early immune cell recruitment for subsequent barrier alterations. Further, using Cx3cr1-GFP mice, we found that intraocular injection of CCL2 increased retinal GFP⁺ monocyte/macrophage infiltration. When these mice were made diabetic, increased infiltration of monocytes/macrophages was also present in retinal tissues. Diabetes and CCL2 injection also induced activation of retinal microglia in these animals. Quantification by flow cytometry demonstrated a two-fold increase of CX3CR1⁺/CD11b⁺ (monocyte/macrophage and microglia) cells in retinas of wildtype diabetic animals in comparison to control non-diabetic ones. Using CCL2 knockout (Ccl2^−/−) mice, we show a significant reduction in retinal vascular leakage and monocyte infiltration following induction of diabetes indicating the importance of this chemokine in alteration of the BRB. Thus, CCL2 may be an important therapeutic target for the treatment of diabetic macular edema.

PKCθ regulates T cell motility via ezrin-radixin-moesin localization to the uropod

Cell motility is a fundamental process crucial for function in many cell types, including T cells. T cell motility is critical for T cell-mediated immune responses, including initiation, activation, and effector function. While many extracellular receptors and cytoskeletal regulators have been shown to control T cell migration, relatively few signaling mediators have been identified that can modulate T cell motility. In this study, we find a previously unknown role for PKCθ in regulating T cell migration to lymph nodes. PKCθ localizes to the migrating T cell uropod and regulates localization of the MTOC, CD43 and ERM proteins to the uropod. Furthermore, PKCθ-deficient T cells are less responsive to chemokine induced migration and are defective in migration to lymph nodes. Our results reveal a novel role for PKCθ in regulating T cell migration and demonstrate that PKCθ signals downstream of CCR7 to regulate protein localization and uropod formation.

Synthesis of oligosaccharide substrates for N-linked glycoprotein processing enzymes

The stereoselective syntheses of one pentasaccharide and one tetrasaccharide containing the Glc-alpha-(1-->3)-Man-alpha moiety as their terminal unit, as well as one tetrasaccharide and one trisaccharide containing the Man-alpha-(1-->2)-Man-alpha terminal unit were accomplished through the utilization of two key glycosyl donors, namely, 4-pentenyl 3-O-acetyl-2,4,6-tri-O-benzyl-alpha-D-mannopyranoside and ethyl 2-O-acetyl-3,4,6-tri-O-benzyl-1-thio-alpha-D-mannopyranoside.