M1/M2 Macrophages in Diabetic Nephropathy: Nrf2/HO-1 as Therapeutic Targets.

The process of inflammation is orchestrated by macrophages, according to their state of differentiation: thus, classically activated (M1) macrophages initiate the process by elaborating proinflammatory cytokines and reactive oxygen species, whereas the latter phase is controlled by alternatively activated macrophages (M2) to resolve inflammation and promote tissue remodelling with the release of growth factors. In a simple human inflammatory response, such as acute crystal arthropathy, macrophages progress linearly through M1 and M2 phases; however, in chronic inflammatory responses, such as atherosclerosis and Diabetic Nephropathy (DN), both M1 and M2 macrophages may coexist, leading to persistent inflammation and fibrosis. A key macrophage receptor that regulates conversion from M1 to M2 is CD163, the hemoglobin scavenger receptor. Scavenging of hemoglobin:haptoglobin (Hb:Hp) complexes via CD163 leads to nuclear translocation of the transcription factor Nrf2 (NF-E2-related factor 2), upregulation of heme oxygenase (HO)-1 cytoprotective protein, and release of interleukin (IL)-10 anti-inflammatory cytokine; IL-10 is then linked in a positive feedback loop to further CD163 expression. The potency of this M1/M2 switching pathway is underscored by the fact that human Hp2 polymorphisms are associated with worsened clinical outcomes for diabetic complications, including DN. Parallel observations in animals show that HO-1 activation by hemin protects against DN in rodent models of diabetes. This review discusses the concept that Nrf2/HO-1 acts as a 'therapeutic funnel' through which a range of natural and synthetic anti-oxidants may drive M1 to M2 switching and improved kidney function in diabetes. We also discuss our observations on the evolution of M1/M2 phenotypes in a human model of wound healing which has presented intriguing potential drug targets for DN, such as eotaxin/CCR3.

Blood viscosity and the expression of inflammatory and adhesion markers in homozygous sickle cell disease subjects with chronic leg ulcers.

OBJECTIVE: To determine differences in TNF-α, IL-1ß, IL-10, sICAM-1 concentrations, leg hypoxia and whole blood viscosity (WBV) at shear rates of 46 sec(-1) and 230 sec(-1) in persons with homozygous S sickle cell disease (SCD) with and without chronic leg ulceration and in AA genotype controls. DESIGN: & METHODS: fifty-five age-matched participants were recruited into the study: 31 SS subjects without leg ulcers (SSn), 24 SS subjects with leg ulcers (SSu) and 18 AA controls. Haematological indices were measured using an AC.Tron Coulter Counter. Quantification of inflammatory, anti-inflammatory and adhesion molecules was performed by ELISA. Measurement of whole blood viscosity was done using a Wells Brookfield cone-plate viscometer. Quantification of microvascular tissue oxygenation was done by Visible Lightguide spectrophotometry. RESULTS: TNF-α and whole blood viscosity at 46 sec(-1) and 230 sec(-1) (1.75, 2.02 vs. 0.83, 1.26, p<0.05) were significantly greater in sickle cell disease subjects than in controls. There were no differences in plasma concentration of sICAM-1, IL-1ß and IL-10 between SCD subjects and controls. IL-1ß (median, IQR: 0.96, 1.7 vs. 0, 0.87; p<0.01) and sICAM-1 (226.5, 156.48 vs. 107.63, 121.5, p<0.005) were significantly greater in SSu group compared with SSn. However there were no differences in TNF-α (2, 3.98 vs. 0, 2.66) and IL-10 (13.34, 5.95 vs. 11.92, 2.99) concentrations between SSu and SSn. WBV in the SSu group at 46 sec(-1) and at 230 Sec 1 were 1.9 (95%CI; 1.2, 3.1) and 2.3 (1.2, 4.4) times greater than in the SSn group. There were no differences in the degree of tissue hypoxia as determined by lightguide spectrophotometry. CONCLUSION: Inflammatory, adhesion markers and WBV may be associated with leg ulceration in sickle cell disease by way of inflammation-mediated vasoocclusion/vasoconstriction. Impaired skin oxygenation does not appear to be associated with chronic ulcers in these subjects with sickle cell disease.

Plasmin Activation of Glial Cells through Protease-Activated Receptor 1.

The objective of this study was to determine whether plasmin could induce morphological changes in human glial cells via PAR1. Human glioblastoma A172 cells were cultured in the presence of plasmin or the PAR1 specific activating hexapeptide, SFLLRN. Cells were monitored by flow cytometry to detect proteolytic activation of PAR1 receptor. Morphological changes were recorded by photomicroscopy and apoptosis was measured by annexinV staining. Plasmin cleaved the PAR1 receptor on glial cells at 5 minutes (P = 0.02). After 30 minutes, cellular processes had begun to retract from the basal substratum and by 4 hours glial cells had become detached. Similar results were obtained by generating plasmin de novo from plasminogen. Morphological transformation was blocked by plasmin inhibitors aprotinin or epsilon-aminocaproic acid (P = 0.03). Cell viability was unimpaired during early morphological changes, but by 24 hours following plasmin treatment 22% of glial cells were apoptotic. PAR1 activating peptide SFLLRN (but not inactive isomer FSLLRN) promoted analogous glial cell detachment (P = 0.03), proving the role for PAR1 in this process. This study has identified a plasmin/PAR1 axis of glial cell activation, linked to changes in glial cell morophology. This adds to our understanding of pathophysiological disease mechanisms of plasmin and the plasminogen system in neuroinjury.

Skin SO2 measurement using visible lightguide spectrophotometry in a black population: a feasibility study.

The aim of the study was to investigate the influence of melanin content on the visible wavelength range spectrophotometric measurement of SO(2) in the skin of normal healthy black and white volunteers. The reactive hyperaemia induced by a 5-minute period of tourniquet occlusion of the brachial artery, as manifested in the change in skin SO(2), was compared with the reactive hyperaemia index (RHI) and arterial stiffness index (AI) as measured using the Endo-PAT2000® peripheral arterial tonometry device. Further measurements were carried out on a diabetic patient with critical ischaemia. The measurements in the normal volunteers and the patient showed that there that there was no correlation between SO(2) and melanin index (r(2) = 0.02). There was a poor correlation between the degree of reactive hyperaemia as assessed using tissue SO(2) measurement and the parameters derived using the Endo-PAT2000® device. Measurements on the critically ischaemic lower limb of the diabetic patient revealed a mean medial/lateral SO(2) of 26.3% and a degree of tissue hypoxia (the percentage of recordings with an SO(2) of 15% or less) of 16.2%. This pilot study demonstrated that the measurement of tissue SO(2) in the skin of black subjects is feasible, not only under conditions of normal perfusion, but also in critical limb ischaemia.

Phenotypic commitment of monocytes towards a protective hemoglobin scavenging phenotype (CD14(pos)CD163(high)HLA-DR(low))following cardiopulmonary bypass.

BACKGROUND: Intravascular hemolysis may cause tissue injury directly or via a systemic inflammatory response. Under physiological conditions, extracorpuscular hemoglobin (Hb) is bound by haptoglobin(Hp) and the complex internalized via the hemoglobin scavenger receptor CD163 on monocytes, prior to catabolism via heme-oxygenase-1 (HO-1). Recently, a novel subset of CD68(pos)CD163(high)HLA-DR(low) macrophages with high expression of HO-1 was recognized in hemorrhagic areas of atherosclerotic plaques, distinct from CD68(pos)CD163(low)HLA-DR(high) foam cell macrophages with low- HO-1 content. Considering the hemolytic insult during CPB, we hypothesized that an equivalent compensatory CD163(high)HLA-DR(low) phenotype will evolve in circulating CD14(pos) monocytes post surgery. METHODS: Twelve patients undergoing elective surgery with CPB were enrolled with informed consent.Whole-blood samples were collected in EDTA at predetermined time-points, pre- intra-, and postoperatively. Whole-blood was evaluated by three-color flow cytometry for expression of CD14, CD163, and HLA-DR; CD14(pos) cells were also permeabilized to detect intracellular HO-1 protein. Plasma [Hp-Hb] concentration was determined by ELISA. RESULTS: A striking phenotypic switch from CD163(low)HLA-DR(high) preoperatively to CD163(high)HLA-DR(low) postoperatively at 24 h was observed on circulating CD14(pos) monocytes. Intracellular HO-1 protein was also significantly up-regulated at 24 h after declamping. These phenotypic changes were preceded by peak Hb-Hp levels observed at 2 h. CONCLUSION: We have shown for the first time, a phenotypic commitment of monocytes towards a protective CD14(pos)CD163(high)HLA-DR(low) population with increased intracellular HO-1 occurring in the circulation during the recovery phase of CPB. These findings have implications for monitoring of anti-inflammatory interventions and linkage to clinical outcomes.