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.

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.