Lipoxygenase product formation and cell adhesion during neutrophil-glomerular endothelial cell interaction

Immune cell behaviour and dynamics in the kidney - insights from in vivo imaging

The actions of immune cells within the kidney are of fundamental importance in kidney homeostasis and disease. In disease settings such as acute kidney injury, anti-neutrophil cytoplasmic antibody-associated vasculitis, lupus nephritis and renal transplant rejection, immune cells resident within the kidney and those recruited from the circulation propagate inflammatory responses with deleterious effects on the kidney. As in most forms of inflammation, intravital imaging - particularly two-photon microscopy - has been critical to our understanding of immune cell responses in the renal microvasculature and interstitium, enabling visualization of immune cell dynamics over time rather than statically. These studies have demonstrated differences in the recruitment and function of these cells from those in more conventional vascular beds, and provided a wealth of information on the actions of blood-borne immune cells such as neutrophils, monocytes and T cells, as well as kidney-resident mononuclear phagocytes, in a range of diseases affecting different kidney compartments. In particular, in vivo imaging has furthered our understanding of leukocyte function within the glomerulus in acute glomerulonephritis, and in the tubulointerstitium and interstitial microvasculature during acute kidney injury and following transplantation, revealing mechanisms of immune surveillance, antigen presentation and inflammation in the kidney.

Bio-imaging and Photodynamic Therapy with Tetra Sulphonatophenyl Porphyrin (TSPP)-TiO2 Nanowhiskers: New Approaches in Rheumatoid Arthritis Theranostics

Since Rheumatoid arthritis (RA) is one of the major human joint diseases with unknown etiology, the early diagnosis and treatment of RA remains a challenge. In this contribution we have explored the possibility to utilize novel nanocomposites of tetera suplhonatophenyl porphyrin (TSPP) with titanium dioxide (TiO₂) nanowhiskers (TP) as effective bio-imaging and photodynamic therapeutic (PDT) agent for RA theranostics. Our observations demonstrate that TP solution PDT have an ameliorating effect on the RA by decreasing significantly the IL-17 and TNF-α level in blood serum and fluorescent imaging could enable us to diagnose the disease in subclinical stages and bio-mark the RA insulted joint.

Dynamic changes in HMGB1 levels correlate with inflammatory responses during cardiopulmonary bypass

High mobility group box 1 (HMGB1), which is released by activated immune cells and necrotic cells, has properties similar to those of pro-inflammatory cytokines. Cardiopulmonary bypass (CPB) induces systemic inflammation and aortic cross-clamping induces myocardial ischemia. This study was conducted to observe the dynamic changes of HMGB1 and tumor necrosis factor (TNF)-α levels during CPB and to analyze their clinical significance. A total of 78 cases of American Society of Anesthesiologists (ASA) grade II-IV undergoing elective valve replacement under CPB were included in this study. Blood and urine samples were collected after anesthesia prior to surgery (T1), before aortic cross-clamping (T2), after CPB (T3) and on the first day after surgery (T4), as well as the second (T5) and third (T6) day after surgery for determination of the levels of HMGB1, TNF-α, alanine aminotransferase (ALT), creatinine (Cr), blood urea nitrogen (BUN), N-acetyl-β-D-glucosamidase (NAG) and β2-microglobulin (β2-MG). Results revealed that: i) the serum levels of HMGB1 elevated as early as T1, increased until reaching a peak at T3, then decreased to a lower level at T4; ii) the serum level of TNF-α was low at T1, gradually increased in a similar manner to HMGB1, then decreased following CPB and reached the lowest point at T5; and iii) the levels of HMGB1 were positively correlated with serum TNF-α and serum ALT at T3. In conclusion, HMGB1 levels may be used as an indicator of inflammation and may be a novel target for controlling inflammation during CPB. The optimal treatment time is T3 (after CPB).

The endogenous pro-resolving mediators lipoxin A4 and resolvin E1 preserve organ function in allograft rejection

Allograft rejection remains a major limitation to successful solid organ transplantation. Here, we investigated the biosynthesis and bioactions of the pro-resolving mediators lipoxin A(4) and resolvin E1 in host responses to organ transplantation. In samples obtained during screening bronchoscopy after human lung transplantation, bronchoalveolar lavage fluid levels of lipoxin A(4) were increased in association with the severity of allograft rejection that was graded independently by clinical pathology. Lipoxin A(4) significantly inhibited calcineurin activation in human neutrophils, and lipoxin A(4) stable analogs prevented acute rejection of vascularized cardiac and renal allografts. Transgenic animals expressing human lipoxin A(4) receptors revealed important sites of action in host tissues for lipoxin A(4)'s protective effects. Resolvin E1 displays counter-regulatory actions for leukocytes, in part, via increased lipoxin A(4) biosynthesis, yet RvE1 administered (1μg, iv) to donor (days -1 and 0) and recipient mice (days -1, 0 and +4) was even more potent than a lipoxin stable analog (1μg, iv) in prolonging renal allograft survival (median survival time=74.0 days with RvE1 and 37.5 days with a LXA(4) analog). Together, these results highlight the potential for pro-resolving mediators in prolonging survival of solid organ transplants.

The role of leukocyte-stromal interactions in chronic inflammatory joint disease

Rheumatoid arthritis (RA) is a debilitating, chronic, persistent inflammatory disease that is characterised by painful and swollen joints. The aetiology of RA is unknown, however whereas past research has concentrated on the role of immune or inflammatory infiltrating cells in inflammation, it is becoming clear that stromal cells play a critical part in regulating the quality and duration of an inflammatory response. In this review we assess the role of fibroblasts within the inflamed synovium in modulating immune responses; in particular we examine the role of stromal cells in the switch from resolving to persistent inflammation as is found in the rheumatoid synovium.

Defining a role for fibroblasts in the persistence of chronic inflammatory joint disease

The most surprising feature of the inflammatory response in rheumatoid arthritis is not that it occurs but that it does not resolve. The persistence of the chronic inflammatory response in conjunction with ongoing joint destruction is an all too familiar finding in many patients with rheumatoid arthritis. Despite the use of effective anti-inflammatory agents and disease modifying drugs, a significant proportion of patients with rheumatoid arthritis continue to have resistant disease. Complete clinical remission is unusual for more than six months and a formal cure of the disease remains elusive. In this report we focus on how attempts to address the question of why rheumatoid arthritis persists have led to a different interpretation of the pathogenesis of rheumatoid disease; one in which alterations in stromal cells such as fibroblasts play an important role in the switch from resolving to persistent disease.

An in vivo approach showing the chemotactic activity of leukotriene B(4) in acute renal ischemic-reperfusion injury

Neutrophil migration protects the body against foreign invasion. Sequestration and activation of neutrophils, however, require stringent regulation because they may also cause tissue damage by the release of lysosomal enzymes and reactive oxygen species. The activity of various chemoattractants [e.g., leukotriene B(4) (LTB(4)), interleukin-8, and complements] has been documented by in vitro assays, whereas in vivo data have been limited mostly to histology. To examine in an in vivo model the chemotactic activity and subsequent tissue infiltration and the role of a specific chemoattractant, LTB(4), we used a rat renal ischemia-reperfusion injury model. Fluorescence-labeled Chinese hamster ovary (CHO) cells stably expressing the LTB(4) receptor (CHO-BLT) were able to accumulate along with neutrophils in the postischemic kidney, in contrast to vector control CHO cells. Furthermore, LTB(4) antagonists that protect against the decrease in renal function and diminish the tissue myeloperoxidase activity also led to the marked decrease in the number of CHO-BLT cells and neutrophils. Thus, LTB(4) alone appears sufficient to cause cells to migrate into postischemic tissues, and its dominant role in reperfusion injury has been demonstrated. The utilization of transfectants to pinpoint the role of LTB(4) in these in vivo experiments suggests their potential use with other ligands and/or in other pathological conditions.

Transfection of rat kidney with human 15-lipoxygenase suppresses inflammation and preserves function in experimental glomerulonephritis

The human 15-lipoxygenase (15-LO) gene was transfected into rat kidneys in vivo via intra-renal arterial injection. Three days later, acute (passive) or accelerated forms of antiglomerular basement membrane antibody-mediated glomerulonephritis were induced in transfected and nontransfected or sham-transfected controls. Studies of glomerular functions (filtration and protein excretion) and ex vivo glomerular leukotriene B(4) biosynthesis at 3 hr, and up to 4 days, after induction of nephritis revealed preservation or normalization of these parameters in transfected kidneys that expressed human 15-LO mRNA and mature protein, but not in contralateral control kidneys or sham-transfected animals. The results provide in vivo-derived data supporting a direct anti-inflammatory role for 15-LO during immune-mediated tissue injury.

Antineutrophil cytoplasmic autoantibodies interact with primary granule constituents on the surface of apoptotic neutrophils in the absence of neutrophil priming

The pathogenic role of antineutrophil cytoplasmic autoantibodies (ANCA) remains controversial because of the difficulty in explaining how extracellular ANCA can interact with intracellular primary granule constituents. It has been postulated that cytokine priming of neutrophils (PMN), as may occur during a prodromal infection, is an important trigger for mobilization of granules to the cell surface, where they may interact with ANCA. We show by electron microscopy that apoptosis of unprimed PMN is also associated with the translocation of cytoplasmic granules to the cell surface and alignment just beneath an intact cell membrane. Immunofluorescent microscopy and FACS analysis demonstrate reactivity of ANCA-positive sera and antimyeloperoxidase antibodies with apoptotic PMN, but not with viable PMN. Moreover, we show that apoptotic PMN may be divided into two subsets, based on the presence or absence of granular translocation, and that surface immunogold labeling of myeloperoxidase occurs only in the subset of PMN showing translocation. These results provide a novel mechanism that is independent of priming, by which ANCA may gain access to PMN granule components during ANCA-associated vasculitis.