Combinatorial model of chemokine involvement in glomerular monocyte recruitment: role of CXC chemokine receptor 2 in infiltration during nephrotoxic nephritis

Afferent neurons of the kidney with impaired firing pattern in inflammation - role of sodium currents?

Peripheral neurons with renal afferents exhibit a predominantly tonic firing pattern of higher frequency that is reduced to low frequencies (phasic firing pattern) in renal inflammation. We wanted to test the hypothesis that the reduction in firing activity during inflammation is due to high-activity tonic neurons switching from higher to low frequencies depending on altered sodium currents. We identified and cultivated afferent sensory neurons with renal projections from the dorsal root ganglia (Th11-L2). Cultivated neurons were incubated with the chemokine CXCL1 (1,5 nmol/ml) for 12 h. We characterized neurons as "tonic," i.e., sustained action potential (AP) firing, or "phasic," i.e., < 5 APs upon stimulation in the current clamp. Their membrane currents were investigated in a voltage clamp. Data analyzed: renal vs. non-renal and tonic vs. phasic neurons. Renal afferent neurons exposed to CXCL1 showed a decrease in tonic firing pattern (CXCL1: 35,6% vs. control: 57%, P < 0.05). Na+ and K+ currents were not different between control renal and non-renal DRG neurons. Phasic neurons exhibited higher Na+ and K+ currents than tonic resulting in shorter APs (3.7 ± 0.3 vs. 6.1 ± 0.6 ms, P < 0.01). In neurons incubated with CXCL1, Na+ and K+ peak current density increased in phasic (Na+: - 969 ± 47 vs. - 758 ± 47 nA/pF, P < 0.01; K+: 707 ± 22 vs. 558 ± 31 nA/pF, P < 0.01), but were unchanged in tonic neurons. Phasic neurons exposed to CXCL1 showed a broader range of Na+ currents ([- 365- - 1429 nA] vs. [- 412- - 4273 nA]; P < 0.05) similar to tonic neurons. After CXCL1 exposure, significant changes in phasic neurons were observed in sodium activation/inactivation as well as a wider distribution of Na+ currents characteristic of tonic neurons. These findings indicate a subgroup of tonic neurons besides mere tonic or phasic neurons exists able to exhibit a phasic activity pattern under pathological conditions.

High CXCR2 expression predicts poor prognosis in adult patients with acute myeloid leukemia

AIMS

This study aimed to assess the associations between clinical parameters, long-term outcomes, and expression of chemokine receptor CXCR2 in patients with acute myeloid leukemia (AML).

METHODS

From May 2013 to May 2017, 83 adult patients newly diagnosed with AML in the Affiliated Hospital of BeiHua University and Jilin Chemical Hospital, were enrolled in this study. The expression of CXCR2 in bone marrow mononuclear cells was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Clinical information and RNA-sequencing datasets of The Cancer Genome Atlas (TCGA) (n = 136) were obtained. The associations between clinical parameters, prognosis, and CXCR2 expression were analyzed.

RESULTS

From both cohorts, patients with AML with M4 and M5 subtypes showed higher CXCR2 expression levels than those with other French-American-British (FAB) subtypes. Patients with extramedullary leukemia infiltration had higher CXCR2 levels than those without. In our cohort, patients with high CXCR2 levels (⩾2.099) had lower relapse-free survival (RFS) (p < 0.000001) and overall survival (OS) (p = 0.000107) than those with low levels (<2.099). High CXCR2 levels (⩾2.082) also indicated a poor OS in the TCGA cohort but only in patients younger than 65 years (5-year OS: 7.7% versus 29.9% in those with CXCR2 levels < 2.082). High CXCR2 levels independently predicted poor prognosis in AML patients, as determined by Cox proportional hazards models.

CONCLUSION

Our results suggest that high CXCR2 expression associates with the monocytic lineage of AML and is an independent risk factor for poor patient prognosis.

Live Imaging of Monocyte Subsets in Immune Complex-Mediated Glomerulonephritis Reveals Distinct Phenotypes and Effector Functions

BACKGROUND

Immune complexes within glomerular capillary walls cause crescentic GN (CrGN). Monocytes and macrophages are important in mediating CrGN, but little work has been done to phenotype the subpopulations involved and determine their respective contributions to glomerular inflammation.

METHODS

Live glomerular imaging using confocal microscopy monitored intravascular monocyte subset behavior during nephrotoxic nephritis (NTN) in a novel WKY-hCD68-GFP monocyte/macrophage reporter rat strain. Flow cytometry and qPCR further analyzed ex vivo the glomerular leukocyte infiltrate during NTN.

RESULTS

Non-classical monocytes surveyed the glomerular endothelium via lymphocyte function-associated antigen 1 (LFA-1) in the steady state. During NTN, non-classical monocytes were recruited first, but subsequent recruitment and retention of classical monocytes was associated with glomerular damage. Monocytes recruited to the glomerular vasculature did not undergo transendothelial migration. This finding suggests that inflammation in immune complex-mediated CrGN is predominantly intravascular, driven by dynamic interactions between intravascular blood monocytes and the endothelium. Glomerular endothelium and non-classical monocytes overexpressed a distinct chemokine axis, which may orchestrate inflammatory myeloid cell recruitment and expression of damage mediators. Reduced classical monocyte recruitment in Lewis rats during NTN confirmed a role for CD16 in mediating glomerular damage.

CONCLUSIONS

Monocyte subsets with distinct phenotypes and effector functions may be important in driving inflammation in experimental CrGN resulting from immune complexes formed within the glomerular capillary wall. LFA-1-dependent endothelial surveillance by non-classical monocytes may detect immune complexes through CD16, orchestrating the inflammatory response through intravascular retention of classical monocytes, which results in glomerular damage and proteinuria.

Adipose‑derived mesenchymal stem cells exhibit tumor tropism and promote tumorsphere formation of breast cancer cells

Mesenchymal stem cells reportedly have a marked effect on tumor growth or suppression. However, it remains uncertain whether adipose-derived mesenchymal stem cells (ADSCs) from grafted fat can contribute to breast cancer growth and recurrence. In the present study, interactions between ADSCs and MCF-7 breast cancer cells were evaluated in a Matrigel co-culture system and in an in vivo nude mouse model. Results suggested that MCF-7 cells exerted tumor tropism effects on ADSCs and this may be regulated by chemokines, such as the macrophage inflammatory protein (MIP)-1δ and MIP-3α. Additionally, ADSCs significantly induced tumorsphere formation in vitro and promoted tumorigenicity in vivo. RT-qPCR analysis indicated that tumorsphere formation by MCF-7 cells was associated with the induction of stem-like properties, which was mediated by epithelial-mesenchymal transition. Together, the present findings indicated that ADSCs exhibit tropism and induce tumorsphere formation of MCF-7 cells.

Radial artery intima-media thickness regresses after secondary prevention interventions in patients' post-acute coronary syndrome and is associated with cardiac and kidney biomarkers

BACKGROUND

Radial artery intima-media thickness (rIMT) measured by ultra-high-resolution ultrasound is associated with increased cardiovascular risk and predicts outcomes. We performed non-invasive high-resolution ultrasound of the radial artery to investigate vascular changes in subjects presenting with acute coronary syndrome (ACS) and who had undergone percutaneous coronary intervention (PCI).

PURPOSE

In the present work, we aimed to follow rIMT change over time post-acute coronary syndrome as a tool to monitor potential response to intensified medical therapy.

METHODS

We examined 256 subjects who underwent PCI due to ACS and healthy controls (n= 39) and we measured a number of biomarkers, which are known to be associated with cardiovascular disease. Images of radial artery were acquired bilaterally in the longitudinal view using a 50 MHz transducer (Vevo 2100 VisualSonics, Inc, Toronto, Ontario, Canada). Carotid IMT (cIMT) and rIMT were measured at <1 month after index PCI followed by a repeated measurement of rIMT at 4 months from the ACS in a sub-set (n=117).

RESULTS

rIMT measured within 1 month post ACS was significantly higher than rIMT after 4 months from ACS, (p < 0.0001), mean ± SD (rIMT right 0.35 ± 0.08; rIMT left 0.37 ± 0.08) vs. (rIMT right 0.29 ± 0.08; rIMT left 0.31 ± 0.09) respectively. There was no statistically significant change in cIMT. In healthy controls there were no changes in rIMT or cIMT overtime. High levels of CX3CL1 and myeloperoxidase measured within one month post ACS are associated with increase of rIMT, r=0.38 (p< 0.0001) and r=0.41 (p< 0.0001) respectively.

CONCLUSIONS

rIMT seem to decrease systemically after ACS and is accompanied with corresponding biomarker change. The cause and clinical implications of the observed decrement in rIMT after ACS need further studies.

Impaired excitability of renal afferent innervation after exposure to the inflammatory chemokine CXCL1

Recently, we showed that renal afferent neurons exhibit a unique firing pattern, i.e., predominantly sustained firing, upon stimulation. Pathological conditions such as renal inflammation likely alter excitability of renal afferent neurons. Here, we tested whether the proinflammatory chemokine CXCL1 alters the firing pattern of renal afferent neurons. Rat dorsal root ganglion neurons (Th11-L2), retrogradely labeled with dicarbocyanine dye, were incubated with CXCL1 (20 h) or vehicle before patch-clamp recording. The firing pattern of neurons was characterized as tonic, i.e., sustained action potential (AP) firing, or phasic, i.e., <5 APs following current injection. Of the labeled renal afferents treated with vehicle, 58.9% exhibited a tonic firing pattern vs. 7.8%, in unlabeled, nonrenal neurons (P < 0.05). However, after exposure to CXCL1, significantly more phasic neurons were found among labeled renal neurons; hence the occurrence of tonic neurons with sustained firing upon electrical stimulation decreased (35.6 vs. 58.9%, P < 0.05). The firing frequency among tonic neurons was not statistically different between control and CXCL1-treated neurons. However, the lower firing frequency of phasic neurons was even further decreased with CXCL1 exposure [control: 1 AP/600 ms (1-2) vs. CXCL1: 1 AP/600 ms (1-1); P < 0.05; median (25th-75th percentile)]. Hence, CXCL1 shifted the firing pattern of renal afferents from a predominantly tonic to a more phasic firing pattern, suggesting that CXCL1 reduced the sensitivity of renal afferent units upon stimulation.

Toll-like receptor 3 signaling contributes to the expression of a neutrophil chemoattractant, CXCL1 in human mesangial cells

BACKGROUND

Mesangial proinflammatory chemokine/cytokine expressions via innate immunity play a pivotal role in the pathogenesis of glomerulonephritis. CXCL1/GROα is a strong neutrophil chemoattractant cytokine and reportedly plays an important role in regional inflammatory reactions. However, detailed signaling of mesangial CXCL1 expression induced by viral or "pseudoviral" immunity remains to be determined.

METHODS

We treated normal human mesangial cells (MCs) in culture with polyinosinic-polycytidylic acid (poly IC), an authentic double-stranded RNA, and analyzed the expression of CXCL1 by reverse transcription-polymerase chain reaction (RT-PCR), real-time quantitative RT-PCR and enzyme-linked immunosorbent assay. To elucidate the poly IC-induced signaling pathway for CXCL1 expression, we subjected the cells to RNA interference against Toll-like receptor (TLR) 3, retinoic acid-inducible gene-I (RIG-I), melanoma differentiation-associated gene 5 (MDA5), interferon (IFN)-β, nuclear factor (NF)-κB p65 and IFN regulatory factor (IRF) 3. We also conducted an immunofluorescence study to examine mesangial CXCL1 expression in biopsy specimens from patients with lupus nephritis (LN) and IgA nephropathy (IgAN).

RESULTS

We found that activation of TLR3 signaling could induce the expression of CXCL1 in MCs. NF-κB, IRF3 and IFN-β, but neither RIG-I nor MDA5, were found to be involved in mesangial CXCL1 expression in this setting. Induction of CXCL1 by poly IC was inhibited by pretreatment of cells with dexamethasone. Intense glomerular CXCL1 expression was observed in biopsy specimens from patients with LN, whereas only a trace staining occurred in specimens from patients with IgAN.

CONCLUSION

TLR3 signaling also contributes to the CXCL1 expression in MCs. These observations further support the implication of viral and "pseudoviral" immunity in the pathogenesis of inflammatory renal diseases, especially in LN.

ELR-CXC chemokine antagonism and cisplatin co-treatment additively reduce H22 hepatoma tumor progression and ameliorate cisplatin-induced nephrotoxicity

Cisplatin (cis-diamminedichloroplatinum) is one of the most commonly used agents for the chemotherapy of various types of cancers, but its use is limited by its dose-dependent side-effects (e.g., nephrotoxicity). The ELR-CXC chemokines are potent tumor growth, metastatic and angiogenic factors and can foster tumor resistance to chemotherapeutic agents. They are also potent proinflammatory agents. The aim of the present study was to evaluate the added effects of combining cisplatin chemotherapy with ELR-CXC chemokine antagonism in a mouse H22 hepatoma cancer cell model. The mice were injected with tumor cells and were then treated with cisplatin (12.5 or 2 mg/kg doses), either alone or together with the chemokine antagonist CXCL8(3-72)K11R/G31P (G31P) (50 µg/kg). At varying time-points renal function was examined using blood urea nitrogen (BUN) and serum creatinine (SCr) as read-outs for the toxic effects of cisplatin, while tumor growth and metastasis were assessed as endpoints. High-dose cisplatin therapy reduced the tumor burden by 52%, while co-delivery of G31P further augmented the tumor growth-suppressive effects of this dose of cisplatin to 71%; G31P by itself and low-dose cisplatin reduced the tumor burden by 19 and 39%, respectively. G31P also reduced the nephrotoxic effects of high-dose cisplatin to the effects observed in the low-dose cisplatin-treated animals. These data confirm the beneficial effects of combined cisplatin chemotherapy and ELR-CXC chemokine anatagonism in the context of both tumor progression and adverse side-effects.

Polymorphisms of CXCL8 and its receptor CXCR2 contribute to the development and progression of childhood IgA nephropathy

Many studies have suggested that CXCL8 and CXCR2 play an important role in the pathogenesis of several types of renal diseases. However, there is no prior study on the association between polymorphisms of these genes and IgA nephropathy (IgAN), especially in children. The genotyping data from 192 patients with childhood IgAN and 397 controls showed significant differences in the frequencies of the CXCL8 gene with rs2227306 (dominant, P = 0.019; overdominant, P = 0.009), rs2227543 (dominant, P = 0.01; overdominant, P = 0.0057), and rs4073 (codominant, P = 0.034; dominant, P = 0.011; overdominant, P = 0.022). In addition, 2 single-nucleotide polymorphism frequencies of the CXCR2 gene (rs4674257 and rs4674259) significantly differed between the patients with pathologically mild and patients with advanced disease. Further, 5 single-nucleotide polymorphisms of the CXCL8 and CXCR2 genes significantly differed in the patients with infiltration of inflammatory cells on the renal biopsy samples. The results of this study suggest that polymorphisms of CXCL8 are associated with increased susceptibility to IgAN, and polymorphisms of CXCR2 with the pathological progression of childhood IgAN. These genetic variations might provide insight into novel individualized antichemokine regimens for treatment.

Targeting the recruitment of monocytes and macrophages in renal disease

Macrophages convert proinflammatory or anti-inflammatory signals of tissue microenvironments into response mechanisms. These response mechanisms largely derive from evolutionary conserved defense programs of innate host defense, wound healing, and tissue homeostasis. Hence, in many settings these programs lead to renal inflammation and tissue remodeling (ie, glomerulonephritis and sclerosis or interstitial nephritis and fibrosis). There is abundant experimental evidence that blocking macrophage recruitment or macrophage activation can ameliorate renal inflammation and fibrosis. In this review we discuss experimental tools to target renal macrophage recruitment by using antagonists against selectins, chemokines, integrins, or other important cytokines that mediate renal injury via macrophage recruitment, some of these already having been used in clinical trials.

Adhesion of renal carcinoma cells to endothelial cells depends on PKCmu

Background

The formation of metastases includes the separation of tumor cells from the primary tumor, cell migration into subendothelial tissue and cell proliferation in secondary organ. In this process, cell adhesion of tumor cells to the endothelium is an essential requirement for formation of metastases. Protein kinase C (PKC) regulates adhesion and proliferation. To identify a relation between PKC isoforms and tumor progression in renal cell carcinoma (RCC), the influence of PKC isoforms on cell adhesion and proliferation, and possible influences of integrins were analyzed in RCC cells.

Methods

The experiments were performed in the RCC cell lines CCF-RC1 and CCF-RC2 after pre-incubation (16 h) with the PKC inhibitors GF109203X (inhibits PKCα, βI, βII, γ, δ and ε), GÖ6976 (inhibits PKCα, βI and μ), RO31-8220 (inhibits PKCα, βI, βII, γ and ε) and rottlerin (inhibits PKCδ). Cell adhesion was assessed through adherence of RCC cells to an endothelial monolayer. Cell proliferation was analyzed by a BrdU incorporation assay. The expression of β1 integrins was analyzed by flow cytometry.

Results

In CCF-RC1 cells, cell adhesion was significantly reduced by GÖ6976 to 55% and by RO31-8220 to 45% of control. In CCF-RC2 cells, only GÖ6976 induced a significant reduction of cell adhesion to 50% of control levels. Proliferation of both cell lines was reduced by rottlerin to 39% and 45% of control, respectively. The β1 integrin expression on the cell surface of CCF-RC1 and CCR-RC2 cells was decreased by RO31-8220 to 8% and 7% of control, respectively. β2 and β3 integrins were undetectable in both cell lines.

Conclusions

The combination of the PKC inhibitors leads to the assumption that PKCμ influences cell adhesion in CCF-RC1 and CCF-RC2 cells, whereas in CCF-RC1 cells PKCε also seems to be involved in this process. The expression of β1 integrins appears to be regulated in particular by PKCε. Cell proliferation was inhibited by rottlerin, so that PKCδ might be involved in cell proliferation in these cells.

Soluble CD40 ligand impairs the function of peripheral blood angiogenic outgrowth cells and increases neointimal formation after arterial injury

BACKGROUND

Recent work has revealed an essential involvement of soluble CD40 ligand (sCD40L) in inflammation and atherosclerosis. We investigated whether sCD40L functionally affects peripheral blood-derived angiogenic early outgrowth cells (EOCs) and neointimal remodeling after arterial injury.

METHODS AND RESULTS

Besides myeloid and endothelial markers, cultured human EOCs strongly expressed CD40 mRNA and protein. EOC adhesion to fibronectin, fibrinogen, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 under flow conditions, as well as their transmigration toward stromal cell-derived factor-1alpha, was dose-dependently reduced after preincubation with recombinant human sCD40L for 24 hours. Integrin expression was unaffected by sCD40L, implying that integrin adhesiveness was attenuated. Surface-immobilized CD40L supported much lower adhesion of EOCs than fibronectin. Treatment of EOCs with sCD40L increased superoxide anion production and decreased viability and proliferation. Notably, CD40(-/-) mice displayed reduced neointima and improved re-endothelialization after carotid wire injury compared with wild-type mice, and therapeutic infusion of control EOCs but not EOCs pretreated with sCD40L attenuated neointimal growth after wire injury in nude mice. Furthermore, neointimal growth was more markedly diminished by infusion of spleen-derived CD40(-/-) mouse EOCs than by that of wild-type EOCs. Preincubation of wild-type EOCs but not CD40(-/-) EOCs with sCD40L before their infusion markedly aggravated neointimal formation. Treatment with sCD40L attenuated luminal incorporation of EOCs and accelerated neointimal progression.

CONCLUSIONS

Endothelial dysfunction due to persistently elevated plasma levels of sCD40L may be attributable to an impairment of EOC function. Hence, in the context of arterial injury, therapeutic blockade of sCD40L may provide a novel strategy for accelerating endothelial regeneration and attenuating neointimal remodeling.

The chemokine Cxcl1 is a novel target gene of parathyroid hormone (PTH)/PTH-related protein in committed osteoblasts

The PTH receptor (PTHR1) is expressed on osteoblasts and responds to PTH or PTHrP in an endocrine or autocrine/paracrine manner, respectively. A microarray study carried out on PTHR1-positive osteoblasts (Kusa 4b10 cells) identified the cysteine-X-cysteine (CXC) family chemokine ligand 1 (Cxcl1) as a novel immediate PTH/PTHrP-responsive gene. Cxcl1 is a potent neutrophil chemoattractant with recognized roles in angiogenesis and inflammation, but a role in bone biology has not been described. Cxcl1 mRNA levels were up-regulated 1 h after either PTH or PTHrP treatment of differentiated Kusa 4b10 osteoblasts (15-fold) and mouse calvarial osteoblasts (160-fold) and in rat metaphyseal bone (5-fold) 1 h after a single sc injection of PTH. Furthermore, PTH treatment stimulated a 10-fold increase in secreted Cxcl1 protein by both Kusa 4b10 cells and calvarial osteoblasts. Immunohistochemistry and PCR demonstrated that CXCR2, the receptor for Cxcl1, is highly expressed in osteoclast precursors (hemopoietic cells) but is predominantly undetectable in the osteoblast lineage, suggesting that osteoblast-derived Cxcl1 may act as a chemoattractant for osteoclast precursors. Confirming this hypothesis, recombinant Cxcl1 dose-dependently stimulated migration of osteoclast precursors in cell culture studies, as did conditioned media from Kusa 4b10 cells treated with PTH. These data indicate that local action through the PTHR1 could stimulate cells of the osteoblast lineage to release a chemokine capable of attracting osteoclast precursors to the bone environment.

Inflammation and tumor microenvironments: defining the migratory itinerary of mesenchymal stem cells

Mesenchymal stem cells (MSC) exhibit tropism for sites of tissue damage as well as the tumor microenvironment. Many of the same inflammatory mediators that are secreted by wounds are found in the tumor microenvironment and are thought to be involved in attracting MSC to these sites. Cell migration is dependent on a multitude of signals ranging from growth factors to chemokines secreted by injured cells and/or respondent immune cells. MSC are likely to have chemotactic properties similar to other immune cells that respond to injury and sites of inflammation. Thus, the well-described model of leukocyte migration can serve as a reasonable example to facilitate the identification of factors involved in MSC migration. Understanding the factors involved in regulating MSC migration to tumors is essential to ultimately develop novel clinical strategies aimed at using MSC as vehicles to deliver antitumor proteins or suppress MSC migration to reduce tumor growth. For example, radiation enhances inflammatory signaling in the tumor microenvironment and may be used to potentiate site-specific MSC migration. Alternatively, restricting the migration of the MSC to the tumor microenvironment may prevent competent tumor-stroma formation, thereby hindering the growth of the tumor. In this review, we will discuss the role of inflammatory signaling in attracting MSC to tumors.

Mechanisms of leukocyte migration across the blood-retina barrier

Immune-mediated inflammation in the retina is regulated by a combination of anatomical, physiological and immuno-regulatory mechanisms, referred to as the blood-retina barrier (BRB). The BRB is thought to be part of the specialised ocular microenvironment that confers protection or "immune privilege" by deviating or suppressing destructive inflammation. The barrier between the blood circulation and the retina is maintained at two separate anatomical sites. These are the endothelial cells of the inner retinal vasculature and the retinal pigment epithelial cells on Bruch's membrane between the fenestrated choroidal vessels and the outer retina. The structure and regulation of the tight junctions forming the physical barrier are described. For leukocyte migration across the BRB to occur, changes are needed in both the leukocytes themselves and the cells forming the barrier. We review how the blood-retina barrier is compromised in various inflammatory diseases and discuss the mechanisms controlling leukocyte subset migration into the retina in uveoretinitis in more detail. In particular, we examine the relative roles of selectins and integrins in leukocyte interactions with the vascular endothelium and the pivotal role of chemokines in selective recruitment of leukocyte subsets, triggering adhesion, diapedesis and migration of inflammatory cells into the retinal tissue.

Stepping out of the flow: capillary extravasation in cancer metastasis

In order for cancer cells to successfully colonize a metastatic site, they must detach from the primary tumor using extracellular matrix-degrading proteases, intravasate and survive in the circulation, evade the immune response, and extravasate the vasculature to invade the target tissue parenchyma, where metastatic foci are established. Though many of the steps of metastasis are widely studied, the precise cellular interactions and molecular alterations associated with extravasation are unknown, and further study is needed to elucidate the mechanisms inherent to this process. Studies of leukocytes localized to inflamed tissue during the immune response may be used to elucidate the process of cancer extravasation, since leukocyte diapedesis through the vasculature involves critical adhesive interactions with endothelial cells, and both leukocytes and cancer cells express similar surface receptors capable of binding endothelial adhesion molecules. Thus, leukocyte extravasation during the inflammatory response has provided a model for transendothelial migration (TEM) of cancer cells. Leukocyte extravasation is characterized by a process whereby rolling mediated by cytokine-activated endothelial selectins is followed by firmer adhesions with beta1 and beta2 integrin subunits to an activated endothelium and subsequent diapedesis, which most likely involves activation of Rho GTPases, regulators of cytoskeletal rearrangements and motility. It is controversial whether such selectin-mediated rolling is necessary for TEM of cancer cells. However, it has been established that similar stable adhesions between tumor and endothelial cells precede cancer cell transmigration through the endothelium. Additionally, there is support for the preferential attachment of tumor cells to the endothelium and, accordingly, site-specific metastasis of cancer cells. Rho GTPases are critical to TEM of cancer cells as well, and some progress has been made in understanding the specific roles of the Rho GTPase family, though much is still unknown. As the mechanisms of cancer TEM are elucidated, new approaches to study and target metastasis may be utilized and developed.

Regulated shedding of transmembrane chemokines by the disintegrin and metalloproteinase 10 facilitates detachment of adherent leukocytes

CX3CL1 (fractalkine) and CXCL16 are unique members of the chemokine family because they occur not only as soluble, but also as membrane-bound molecules. Expressed as type I transmembrane proteins, the ectodomain of both chemokines can be proteolytically cleaved from the cell surface, a process known as shedding. Our previous studies showed that the disintegrin and metalloproteinase 10 (ADAM10) mediates the largest proportion of constitutive CX3CL1 and CXCL16 shedding, but is not involved in the phorbolester-induced release of the soluble chemokines (inducible shedding). In this study, we introduce the calcium-ionophore ionomycin as a novel, very rapid, and efficient inducer of CX3CL1 and CXCL16 shedding. By transfection in COS-7 cells and ADAM10-deficient murine embryonic fibroblasts combined with the use of selective metalloproteinase inhibitors, we demonstrate that the inducible generation of soluble forms of these chemokines is dependent on ADAM10 activity. Analysis of the C-terminal cleavage fragments remaining in the cell membrane reveals multiple cleavage sites used by ADAM10, one of which is preferentially used upon stimulation with ionomycin. In adhesion studies with CX3CL1-expressing ECV-304 cells and cytokine-stimulated endothelial cells, we demonstrate that induced CX3CL1 shedding leads to the release of bound monocytic cell lines and PBMC from their cellular substrate. These data provide evidence for an inducible release mechanism via ADAM10 potentially important for leukocyte diapedesis.

Role of asymmetric dimethylarginine in inflammatory reactions by angiotensin II

Previous investigations have demonstrated that angiotensin (Ang) II induces inflammatory reactions and asymmetric dimethylarginine (ADMA), an endogenous NOS inhibitor, might be a novel inflammatory factor. Endothelial cell activation was induced by incubation with Ang II or ADMA. Incubation with Ang II (10(-6) M) for 24 h elevated the levels of ADMA and decreased the levels of nitrite/nitrate concomitantly with a significant increase in the expression of protein arginine methyltransferase and a decrease in the activity of dimethylarginine dimethylaminohydrolase (DDAH). Exposure to Ang II (10(-6) M for 24 h) also enhanced intracellular ROS elaboration and the levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-8, upregulated chemokine receptor CXCR2 mRNA expression, increased adhesion of endothelial cells to monocytes and induced a significant increase in the activity of nuclear factor (NF)-kappaB, which was attenuated by pretreatment with the Ang II receptor blocker losartan (1, 3 and 10 muM). Exogenous ADMA (30 microM) also increased ROS generation and the levels of TNF-alpha and IL-8, decreased the levels of nitrite/nitrate, upregulated CXCR2 gene expression, increased endothelial cell binding with monocytes and activated the NF-kappaB pathway, which was inhibited by pretreatment with losartan or L-arginine. These data suggest that ADMA is a potential proinflammatory factor and may be involved in the inflammatory reaction induced by Ang II.

Importance of CXC Chemokine Receptor 2 in the Homing of Human Peripheral Blood Endothelial Progenitor Cells to Sites of Arterial Injury

Circulating endothelial progenitor cells (EPCs) may contribute to endothelial regeneration; however, the exact mechanisms of their arterial homing remain elusive. We examined the role of the angiogenic chemokine receptor CXCR2 in the homing of human EPCs. Isolated EPCs expressed CXCR2 together with kinase insert domain-containing receptor, CD31, vascular endothelial cadherin, and CXCR4. Adhesion assays under flow conditions showed that EPCs preferentially adhered to beta(2)-integrin ligands, that firm arrest on fibronectin or fibrinogen was enhanced by the CXCR2 ligands CXCL1 or CXCL7, and that blockade of CXCR2 significantly reduced EPC adhesion on platelet-coated endothelial matrix. This was corroborated by the involvement of CXCR2 in EPC recruitment to denuded areas of murine carotid arteries ex vivo and in vivo. Notably, blocking CXCR2 inhibited the incorporation of human EPCs expressing CXCR2 at sites of arterial injury in athymic nude mice. Immunoreactivity for the beta-thromboglobulin isoform CXCL7 was observed in murine platelets and denuded smooth muscle cells (SMCs) early after wire injury, and transcripts for CXCL7 and CXCL1 were detected in isolated human arterial SMCs. Human KDR(+)CXCR2(+) cells showed better in situ adhesion to injured murine carotid arteries than KDR(+)CXCR2(-) cells, were predominantly CD14(+), and improved CXCR2-dependent endothelial recovery after injury in nude mice. In conclusion, our data clearly demonstrate the importance of CXCR2 for the homing of circulating EPCs to sites of arterial injury and for endothelial recovery in vivo.

Interaction between proximal tubular epithelial cells and infiltrating monocytes/T cells in the proteinuric state

We hypothesize an interaction between T cells/monocytes and the tubules in the development of tubulointerstitial injury in chronic proteinuric nephropathy. We established in vitro co-culture systems of proximal tubular epithelial cells (PTEC) and T cells/monocytes to study the contribution of soluble factors and cell-to-cell contact in the development of tubulointerstitial injury. The release of monocyte chemoattractant protein-1 (MCP1 or CCL2), Regulated upon Activation, normal T cell Expressed and Secreted (RANTES or CCL5), soluble intracellular adhesion molecules-1 (sICAM-1), or interleukin-6 (IL-6) was increased in PTEC following apical exposure to human serum albumin (HSA). The release of CCL2, CCL5, or sICAM-1 from PTEC was enhanced by contact of monocytes/T cells on the basolateral surface. Tumor necrosis factor-alpha (TNF-alpha) and IL-1beta are important soluble factors as suggested by the blocking effect of antibodies (Abs) against TNF-alpha or IL-1beta but not against other cytokines. The percentage of CD4+ T cells expressing both chemokine receptors, CCR2 and CCR5, was increased after culturing with supernatant from the apical or basolateral surface of PTEC following apical exposure to HSA. However, only CCR2 was upregulated in CD8+ T cells, whereas CCR5 expression was increased in monocytes. The chemotaxis of CD4+ or CD8+ T cells to supernatant from PTEC upon apical exposure to HSA was reduced with neutralizing Abs against CCL5 and/or CCL2, whereas the chemotaxis of monocytes was only reduced by anti-CCL5 but not by anti-CCL2. In summary, chemokines released by HSA-activated PTEC are amplified by monocytes/T cells. Mediators released by HSA-activated PTEC can differentially modulate the expression of chemokine receptors in monocytes/T cells and hence, alter their chemotaxis towards activated PTEC. These interactions are pivotal in the development of tubulointerstitial injury.

Chemokines: inflammatory mediators of atherosclerosis

Atherosclerosis as the underlying mechanisms of myocardial infarction, stroke and peripheral artery disease remains the major cause of morbidity and mortality in developed countries. Recent developments in vascular biology have indicated that atherosclerosis can be best characterized as a chronic inflammatory disease of the vessel wall that promotes lesion development and progression. Chemokines regulate and control these processes by orchestrating adhesive interactions of circulating blood cells with the arterial wall and their subsequent extravasation. Exhibiting a high degree of specialization and cooperation, different chemokines mediate distinct steps during the atherogenic recruitment of monocytes and T cells. This diversity of chemokine expression and function might lead to the identification of selective therapeutic targets for the prevention and treatment of atherosclerosis.

Role for macrophage metalloelastase in glomerular basement membrane damage associated with alport syndrome

Alport syndrome is a glomerular basement membrane (GBM) disease caused by mutations in type IV collagen genes. A unique irregular thickening and thinning of the GBM characterizes the progressive glomerular pathology. The metabolic imbalances responsible for these GBM irregularities are not known. Here we show that macrophage metalloelastase (MMP-12) expression is >40-fold induced in glomeruli from Alport mice and is markedly induced in glomeruli of both humans and dogs with Alport syndrome. Treatment of Alport mice with MMI270 (CGS27023A), a broad spectrum MMP inhibitor that blocks MMP-12 activity, results in largely restored GBM ultrastructure and function. Treatment with BAY-129566, a broad spectrum MMP inhibitor that does not inhibit MMP-12, had no effect. We show that inhibition of CC chemokine receptor 2 (CCR2) receptor signaling with propagermanium blocks induction of MMP-12 mRNA and prevents GBM damage. CCR2 receptor is expressed in glomerular podocytes of Alport mice, suggesting MCP-1 activation of CCR2 on podocytes may underlie induction of MMP-12. These data indicate that the irregular GBM that characterizes Alport syndrome may be mediated, in part, by focal degradation of the GBM due to MMP dysregulation, in particular, MMP-12. Thus, MMP-12/CCR2 inhibitors may provide a novel and effective therapeutic stra-tegy for Alport glomerular disease.

Neutrophils, lymphocytes, and monocytes exhibit diverse behaviors in transendothelial and subendothelial migrations under coculture with smooth muscle cells in disturbed flow

Atherosclerosis develops at regions of the arterial tree exposed to disturbed flow. The early stage of atherogenesis involves the adhesion of leukocytes (white blood cells [WBCs]) to and their transmigration across endothelial cells (ECs), which are located in close proximity to smooth muscle cells (SMCs). We investigated the effects of EC/SMC coculture and disturbed flow on the adhesion and transmigration of 3 types of WBCs (neutrophils, peripheral blood lymphocytes [PBLs], and monocytes) using our vertical-step flow (VSF) chamber, in which ECs were cocultured with SMCs in collagen gels. Such coculture significantly increased the adhesion and transmigration of neutrophils, PBLs, and monocytes under VSF, particularly in the reattachment area, where the rolling velocity of WBCs and their transmigration time were decreased, as compared with the other areas. Neutrophils, PBLs, and monocytes showed different subendothelial migration patterns under VSF. Their movements were more random and shorter in distance in the reattachment area. Coculture of ECs and SMCs induced their expressions of adhesion molecules and chemokines, which contributed to the increased WBC adhesion and transmigration. Our findings provide insights into the mechanisms of WBC interaction with the vessel wall (composed of ECs and SMCs) under the complex flow environments found in regions of prevalence for atherogenesis.

Distribution of dendritic cells and expression of chemokines in mouse models of mucosal immune in vivo

AIM: To investigate the migration, distribution and morphological characteristics of dendritic cells (DCs) and the expression of chemokines in the mouse models of mucosal immune.

METHODS: The distribution and morphological characteristics of DCs in the mouse models were observed by light microscopy, immunohistochemical method, and in situ hybridization staining. The expression of S-100 protein, monocyte chemotactic protein-1(MCP-1), regulated upon activation, normal T cell expressed and secreted chemokine (Rantes), macrophage inflammatory protein-1β(MIP-1β) mRNA and C-C chemokine receptor 7(CCR7) mRNA were analyzed.

RESULTS: The in vivo DCs were mainly located in the mesenteric lymph node(MLN), Peyer's Patch(PP), and tissues of gut in the mouse model of mucosal immune. The number of DCs was significantly larger in the model group than that in the controls(35.32 ± 3.17 vs 15.03 ± 1.81, 29.14 ± 2.03 vs 11.35 ± 0.97, 27.96 ± 1.97 vs 9.86 ± 0.82, P < 0.01). The expression of MCP-1, Rantes, MIP-1βmRNA and CCR7 mRNA in the mucosal immune mice were significantly increased, and their number and area densities were markedly higher than those the controls.

CONCLUSION: The in vivo DCs can migrate and gather to the MLN, PP and gut in the mucosal immune mice, and the expression of MCP-1, Rantes, MIP-1βmRNA and CCR7 mRNA are significantly elevated.

Increased expression of chemokine KC, an interleukin-8 homologue, in a model of oxygen-induced retinopathy

PURPOSE

The purpose of this study was to determine the retinal expression of angiogenic chemokines/cytokines in a mouse model of oxygen-induced retinopathy.

METHODS

C57BL/6 (B6) mice were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and then recovered in room air. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine relative mRNA levels of KC, macrophage inflammatory protein-2 (MIP-2), interleukin-1alpha (IL-1alpha), and interferon gamma (IFN-gamma). Immunohistochemistry was used to localize KC in the retina. IL-1alpha was also injected into the vitreous of mouse eyes, and KC expression was examined by RT-PCR, enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry.

RESULTS

KC expression at both the mRNA and protein levels was increased in P14, P17, and P21 of hyperoxia-injured eyes. KC immunoreactivity was localized along the nerve fiber layer and in radial Müller cell processes. IL-1alpha mRNA was modestly increased in hyperoxia-injured eyes on P14 and P17. INF-gamma mRNA was not detected in the retina. Adult mouse eyes injected with IL-1alpha demonstrated increased levels of both KC mRNA and protein, with KC immunoreactivity localized to Müller cell processes.

CONCLUSIONS

Oxygen-induced injury to the developing retina results in the induction of the CXC chemokine KC at both the mRNA and protein levels during the peak time points of neovascularization, suggesting a possible role in the pathogenesis of retinopathy of prematurity.

Glomerulonephritis

The term glomerulonephritis encompasses a range of immune-mediated disorders that cause inflammation within the glomerulus and other compartments of the kidney. Studies with animal models have shown the crucial interaction between bone-marrow-derived inflammatory cells and cells intrinsic to the kidney that is both fundamental and unique to the pathogenesis of glomerulonephritis. The mechanisms of interaction between these cells and the mediators of their coordinated response to inflammation are being elucidated. Despite these pathophysiological advances, treatments for glomerulonephritis remain non-specific, hazardous, and only partly successful. Glomerulonephritis therefore remains a common cause of end-stage kidney failure worldwide. Molecule-specific approaches offer hope for more effective and safer treatments in the future.

Inflammatory mediators in atherosclerotic vascular disease

An impressive body of work has established the current paradigm of atherosclerosis as an inflammatory process that promotes lesion development and progression. Early atheroma formation is characterized by leukocyte recruitment and expression of inflammatory mediators which is confounded in the context of hyperlipidemia. Evidence for an involvement of both innate and adaptive immunity in lesion formation has emerged, supporting a causal relation between the balance of pro- and anti-inflammatory cytokines and atherogenesis. The function of chemokines in distinct steps during mononuclear cell recruitment to vascular lesions has been studied in genetically deficient mice and other suitable models, and displays a high degree of specialization and cooperation. The contribution of platelet chemokines deposited on endothelium to monocyte arrest, differences in the presentation and involvement of chemokines between native and neointimal lesion formation, and related functions of macrophage migration inhibitory factor, a cytokine with striking structural homology to chemokines are of note. A novel role of chemokines in the recruitment of vascular progenitors during neointimal hyperplasia and in the recovery of endothelial denudation underscores their relevance for atherosclerotic vascular disease. The functional diversity of chemokines in vascular inflammation may potentially allow the selective therapeutic targeting of different atherosclerotic conditions.

Prospective study of neutrophil chemokine responses in trauma patients at risk for pneumonia

Neutrophil hyperactivity contributes to organ failure, whereas hypofunction permits sepsis. The chemokine receptors CXCR1 and CXCR2 are central to polymorphonuclear neutrophil (PMN) function. We prospectively assessed CXCR function and expression in PMNs from trauma patients at high risk for pneumonia and their matched volunteer controls. CXCR2-specific calcium flux and chemotaxis were desensitized by injury, returning toward normal after 1 week. CXCR1 responses were relatively maintained. These defects appeared to be caused by preferential suppression of CXCR2 surface expression. To evaluate potential mechanisms of in vivo chemokine receptor regulation further we studied cross-desensitization of chemokine receptors in normal PMNs. Susceptibility to desensitization was in the order CXCR2 > CXCR1 > formyl peptide or C5a receptors. Trauma desensitizes CXC receptors, with CXCR2 being especially vulnerable. Desensitization is most marked immediately postinjury, generally resolving by Day 7. High-affinity chemoattractant receptors responsible for PMN chemotaxis from bloodstream to tissue appear to be regulated by injury. Receptors for end-target chemoattractants regulate CXCR1 and CXCR2 but resist suppression themselves and respond normally after injury. CXCR2 desensitization occurs before pneumonia, which developed in 44% of these patients. Suppression of high-affinity PMN receptors, like CXCR2, may predispose to pneumonia after trauma or other inflammatory conditions that lead to systemic inflammatory response syndrome.

Multiple facets of macrophages in renal injury

Macrophage infiltration is a common feature of renal disease and their presence has been synonymous with tissue damage and progressive renal failure. More recently work has focused on the heterogeneity of macrophage activation and in particular their ability to curtail inflammation and restore normal function. This has led to the view that it is macrophage function rather than their number that is important in determining the outcome of inflammatory disease. This review will focus on the pathways that regulate macrophage infiltration and activation and how these could be manipulated to control renal inflammatory disease. In particular, the ability of specific cell surface receptors and intracellular signaling pathways to control macrophage activation and how macrophages can be genetically manipulated to develop properties that favor resolution over ongoing injury.

Chemokines

Understanding the increasingly complex role of chemokines in various manifestations of atherosclerotic vascular disease and the apparent redundancy in their expression requires improved concepts defining the specialization and cooperation of chemokines in regulating the recruitment of mononuclear cells to vascular lesions. In an attempt to elaborate such models, this review highlights recent insights into the functional role of chemokines in mediating distinct steps during the atherogenic recruitment of monocytes and T cells obtained in genetically deficient mice and in suitable models. A particular focus is placed on the contribution of platelet chemokines deposited on endothelium for monocyte arrest, on differences in the involvement of chemokines between recruitment to native lesions and to neointimal lesions after arterial injury, and on closely related functions of macrophage migration inhibitory factor, a cytokine with considerable structural homology to chemokines. As an evolving aspect of atherosclerotic vascular disease, a role of chemokines, foremost stromal cell-derived factor-1alpha, in the recruitment of mononuclear progenitors of vascular cells during neointimal hyperplasia, endothelial recovery, and angiogenesis is discussed. The functional diversity and pleiotropy of chemokines in and beyond mononuclear cell recruitment awaits further elucidation to enable therapeutic targeting of atherogenesis by context-specific blockade of nonoverlapping chemokine receptor pairs.

Heparan sulfate proteoglycans in glomerular inflammation

Heparan sulfate proteoglycans (HSPGs) are glycoproteins consisting of a core protein to which linear heparan sulfate side chains are covalently attached. These heparan sulfate side chains can be modified at different positions by several enzymes, which include N-deacetylases, N- and O-sulfotransferases, and an epimerase. These heparan sulfate modifications give rise to an enormous structural diversity, which corresponds to the variety of biologic functions mediated by heparan sulfate, including its role in inflammation. The HSPGs in the glomerular basement membrane (GBM), perlecan, agrin, and collagen XVIII, play an important role in the charge-selective permeability of the glomerular filter. In addition to these HSPGs, various cell types express HSPGs at their cell surface, which include syndecans, glypicans, CD44, and betaglycan. During inflammation, HSPGs, especially heparan sulfate, in the extracellular matrix (ECM) and at the surface of endothelial cells bind chemokines, which establishes a local concentration gradient recruiting leukocytes. Endothelial and leukocyte cell surface HSPGs also play a role in their direct adhesive interactions via other cell surface adhesion molecules, such as selectins and beta2 integrin. Activated leukocytes and endothelial cells exert heparanase activity, resulting in degradation of heparan sulfate moieties in the ECM, which facilitates leukocyte passage into tissues and the release of heparan sulfate-bound factors. In various renal inflammatory diseases the expression of agrin and GBM-associated heparan sulfate is decreased, while the expression of CD44 is increased. Heparan sulfate or heparin preparations affect inflammatory cell behavior and have promising therapeutic, anti-inflammatory properties by preventing leukocyte adhesion/influx and tissue damage.

Identifying Chemokines as Therapeutic Targets in Renal Disease: Lessons from Antagonist Studies and Knockout Mice

Chemokines, in concert with cytokines and adhesion molecules, play multiple roles in local and systemic immune responses. In the kidney, the temporal and spatial expression of chemokines correlates with local renal damage and accumulation of chemokine receptor-bearing leukocytes. Chemokines play important roles in leukocyte trafficking and blocking chemokines can effectively reduce renal leukocyte recruitment and subsequent renal damage. However, recent data indicate that blocking chemokine or chemokine receptor activity in renal disease may also exacerbate renal inflammation under certain conditions. An increasing amount of data indicates additional roles of chemokines in the regulation of innate and adaptive immune responses, which may adversively affect the outcome of interventional studies. This review summarizes available in vivo studies on the blockade of chemokines and chemokine receptors in kidney diseases, with a special focus on the therapeutic potential of anti-chemokine strategies, including potential side effects, in renal disease.

Gene delivery of the elastase inhibitor elafin protects macrophages from neutrophil elastase-mediated impairment of apoptotic cell recognition

The resolution of inflammation is dependent on recognition and phagocytic removal of apoptotic cells by macrophages. Receptors for apoptotic cells are sensitive to degradation by human neutrophil elastase (HNE). We show in the present study that HNE cleaves macrophage cell surface CD14 and in so doing, reduces phagocytic recognition of apoptotic lymphocytic cells (Mutu 1). Using an improved method of adenovirus-mediated transfection of macrophages with the HNE inhibitor elafin, we demonstrate that elafin overexpression prevents CD14 cleavage and restores apoptotic cell recognition by macrophages. This approach of genetic modification of macrophages could be used to restore apoptotic cell recognition in inflammatory conditions.

Chemokines in innate and adaptive host defense: basic chemokinese grammar for immune cells

Chemokines compose a sophisticated communication system used by all our cell types, including immune cells. Chemokine messages are decoded by specific receptors that initiate signal transduction events leading to a multitude of cellular responses, leukocyte chemotaxis and adhesion in particular. Critical determinants of the in vivo activities of chemokines in the immune system include their presentation by endothelial cells and extracellular matrix molecules, as well as their cellular uptake via "silent" chemokine receptors (interceptors) leading either to their transcytosis or to degradation. These regulatory mechanisms of chemokine histotopography, as well as the promiscuous and overlapping receptor specificities of inflammation-induced chemokines, shape innate responses to infections and tissue damage. Conversely, the specific patterns of homeostatic chemokines, where each chemokine is perceived by a single receptor, are charting lymphocyte navigation routes for immune surveillance. This review presents our current understanding of the mechanisms that regulate the cellular perception and pathophysiologic meaning of chemokines.

Deep vein thrombosis resolution is modulated by monocyte CXCR2-mediated activity in a mouse model

OBJECTIVE

To determine the role of CXCR2, the receptor for cysteine-X-cysteine (CXC) chemokines, and its primary effector cell, the neutrophil (PMN), on deep venous thrombosis (DVT) resolution.

METHODS AND RESULTS

DVT in BALB/c, anti-CXCR2 antibody-treated, and BALB/c CXCR2(-/-) mice were created by infrarenal inferior vena cava (IVC) ligation and the thrombus harvested at various time points over 21 days. The CXCR2(-/-) mice had significantly larger thrombi at early time points (days 2 to 8), and significantly decreased intrathrombus PMNs, monocytes, and neovascularization as compared with controls. Thrombus KC/CXCL1 was significantly higher at 2 days in CXCR2-/- thrombi as measured by enzyme-linked immunosorbent assay. Fibrin content was significantly higher, with less uPA gene expression at 4 days in CXCR2-/- thrombi. Late fibrotic maturation of the thrombus was delayed in the CXCR2-/- mice, with significantly decreased 8 day MMP-2 activity, whereas MMP-9 activity was elevated as compared with controls. Similar impairment in DVT resolution was found at 8 days with anti-CXCR2 inhibition. However, systemic neutropenia, unlike CXCR2 deletion, did not increase the thrombus size as compared with controls.

CONCLUSIONS

Normal DVT resolution involves CXCR2-mediated neovascularization, collagen turnover, and fibrinolysis, and it is probably primarily monocyte-dependent.

Molecular response to cytotoxic injury: role of inflammation, MAP kinases, and endoplasmic reticulum stress response

Nephrotoxicants have varied direct and indirect effects on the vasculature, tubules, and interstitium of the kidney. In most cases the molecular components of the toxic insult are poorly understood. In this review some common themes of injury, repair, and adaptive protective responses that represent characteristic responses of the cells and kidney tissue that transcend the specifics of a particular toxin are presented. Particular attention is paid to the vascular and inflammatory aspects of nephrotoxicity as well as the activation of the MAP kinase families and the endoplasmic reticulum stress response by the tubular epithelial cell.

Cytokines, chemokines, and cell adhesion molecules in inflammatory myopathies

The inflammatory myopathies include dermatomyositis (DM), polymyositis (PM), and sporadic inclusion-body myositis (s-IBM). In DM, the main immune effector response appears to be humoral and directed against the microvasculature, whereas in both PM and s-IBM, cytotoxic CD8+ T cells and macrophages invade and eventually destroy nonnecrotic muscle fibers expressing major histocompatibility complex class I. The need for more specific and safer therapies in inflammatory myopathies has prompted researchers to better decipher the molecular events associated with inflammation and muscle fiber loss in these diseases. The complex specific migration of leukocyte subsets to target tissues requires a coordinated series of events, namely activation of leukocytes, adhesion to the vascular endothelium, and migration. Cell adhesion molecules (CAM) and chemokines play a major role in this multistep process. In addition, cytokines by stimulating CAM expression and orchestrating T-cell differentiation also influence the immune response. This review focuses on recent advances in defining the molecular events involved in leukocyte trafficking in inflammatory myopathies. Specific topics include a concise summary of clinical features, pathological findings and immunopathology observed in inflammatory myopathies, background information about cytokines, chemokines and cell adhesion molecules, and the expression of these molecules in inflammatory myopathies.

Expression of CX3CL1/fractalkine by mesangial cells in vitro and in acute anti-Thy1 glomerulonephritis in rats

BACKGROUND

Mesangial cells (MCs) can promote glomerular macrophage accumulation in glomerulonephritis through production of a variety of chemokines. This study investigated the potential of MCs to synthesize CX3CL1/fractalkine, a CX3C chemokine, both in vitro and in acute anti-Thy1 glomerulonephritis in rats.

METHODS

Anti-Thy1 glomerulonephritis was induced in Wistar rats by a single injection of mouse anti-rat Thy1.1 antibody intravenously. Glomerular mRNAs for CX3CL1/fractalkine, CCL2/monocyte chemoattractant protein (MCP)-1, and their cognate receptors, CX3CR1 and CCR2, were determined by northern blot analysis or reverse-transcription polymerase chain reaction. CX3CL1/fractalkine mRNA and protein expression in vivo was localized by in situ hybridization and immunohistochemistry. Monocytes/macrophages and activated MCs were detected by immunohistochemistry. Regulation of CX3CL1/fractalkine expression in cultured MCs was determined by northern and western blot analysis.

RESULTS

After induction of anti-Thy1 disease, glomerular CX3CL1/fractalkine mRNA was significantly up-regulated, peaking at 2 h and sustaining into day 5 of the nephritis. A corresponding increase in urinary CX3CL1/fractalkine protein was evident after day 1 of the nephritis, but became more prominent during the MC proliferative phase (days 3-5). Meanwhile, induction of glomerular CCL2/MCP-1 mRNA and urinary CCL2/MCP-1 protein occurred within 24 h, and was barely detectable after day 3 of the nephritis. Urinary CCL2/MCP-1, but not CX3CL1/fractalkine, correlated with glomerular macrophage accumulation (r = 0.936, P<0.01) and glomerular CCR2 mRNA expression (r = 0.965, P<0.01). In contrast, only urinary CX3CL1/fractalkine coincided temporally to glomerular mRNA for CX3CR1 (r = 0.809, P < 0.01). Combined in situ hybridization and immunohistochemistry revealed that activated MCs were a major source for CX3CL1/fractalkine mRNA and protein during days 3-5 of the nephritis. Incubation of cultured MCs with tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, platelet-derived growth factor (PDGF)-AB or basic fibroblast growth factor (bFGF) significantly up-regulated CX3CL1/fractalkine mRNA and protein expression. This cytokine- and growth factor-stimulated CX3CL1/fractalkine expression could be abolished by the nuclear factor-kappaB inhibitors, curcumin and MG132.

CONCLUSIONS

Our data demonstrate that activated MCs are a source for the augmented glomerular CX3CL1/fractalkine expression during the proliferative phase of acute anti-Thy1 glomerulonephritis. Up-regulation of MC CX3CL1/fractalkine by TNF-alpha, IL-1beta, PDGF-AB and bFGF is mediated, at least in part, via the nuclear factor-kappaB signalling pathway. The differential expression of CCL2/MCP-1 and CX3CL1/fractalkine may sequentially recruit distinct subsets of monocytes to the glomerulus during acute anti-Thy1 glomerulonephritis.

Potential new drugs for therapy of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is a major health problem with cigarette smoking as its major risk factor. Current therapies are directed against the symptoms (e.g., breathlessness and mucus production) or the chronic airway inflammation. However, the excessive annual decline in lung function and the airway inflammation have not yet been shown to be improved by these strategies. New potential drug therapies are directed against specific components of the inflammation. Novel drugs have been developed for treatment of inflammatory diseases including chronic obstructive pulmonary disease in order to antagonise cytokines and chemokines such as TNF-alpha, CXC chemokine ligand 8 (IL-8) or CC chemokine ligand 2 (monocyte chemoattractant protein 1) that orchestrate the inflammatory process. Some of these drugs are shown to be effective in patients with other chronic inflammatory diseases but still have to prove their efficacy in the treatment of chronic obstructive pulmonary disease.

CXCR2 regulates respiratory syncytial virus-induced airway hyperreactivity and mucus overproduction

Severe inflammation and mucus overproduction are partially responsible for respiratory syncytial virus (RSV)-induced disease in infants. Using a murine model, we characterized the virally induced chemokine receptors responsible for mediating the pathophysiological response to RSV infection, we found that CXCR2 mRNA was induced at 4 days after RSV infection. Immunohistochemical staining demonstrated that CXCR2 protein was expressed on alveolar macrophages. Immunoneutralization of CXCR2 resulted in decreased airway hyperreactivity relative to the RSV-infected controls. In addition, there was decreased mucus in the bronchoalveolar lavage fluid, decreased periodic-acid Schiff staining, and significantly less mucus-associated gob-5 mRNA and protein in anti-CXCR2-treated mice. The effects of anti-CXCR2 treatment were not a result of differences in viral clearance or neutrophil influx, as these parameters were comparable in both groups of animals. To confirm our immunoneutralization studies, we performed experiments in CXCR2(-/-) mice. Results in CXCR2(-/-) mice recapitulated results from our immunoneutralization studies. However, CXCR2(-/-) mice also showed a statistically significant decrease in muc5ac, relative to RSV-infected wild-type animals. Thus, CXCR2 may be a relevant target in the pathogenesis of RSV bronchiolitis, since it contributes to mucus production and airway hyperreactivity in our model of RSV infection.

Albumin stimulates interleukin-8 expression in proximal tubular epithelial cells in vitro and in vivo

Renal tubulointerstitial injury is characterized by inflammatory cell infiltrate; however, the stimuli for leukocyte recruitment are not fully understood. IL-8 is a potent chemokine produced by proximal tubular epithelial cells (PTECs). Whether nephrotic proteins stimulate tubular IL-8 expression remains unknown. Acute exposure of human PTECs to albumin induced IL-8 gene and protein expression time- and dose-dependently. Apical albumin predominantly stimulated basolateral IL-8 secretion. Electrophoretic mobility shift assay demonstrated nuclear translocation of NF-kappaB, and the p65/p50 subunits were activated. NF-kappaB activation and IL-8 secretion were attenuated by the NF-kappaB inhibitors pyrrolidine dithiocarbamate and cell-permeable peptide. Albumin upregulated intracellular reactive oxygen species (ROS) generation, while exogenous H2O2 stimulated NF-kappaB translocation and IL-8 secretion. Albumin-induced ROS generation, NF-kappaB activation, and IL-8 secretion were endocytosis- and PKC-dependent as these downstream events were abrogated by the PI3K inhibitors LY294002 and wortmannin, and the PKC inhibitors GF109203X and staurosporin, respectively. In vivo, IL-8 mRNA expression was localized by in situ hybridization to the proximal tubules in nephrotic kidney tissues. The intensity of IL-8 immunostaining was higher in nephrotic than non-nephrotic subjects. In conclusion, albumin is a strong stimulus for tubular IL-8 expression, which occurs via NF-kappaB-dependent pathways through PKC activation and ROS generation.

Chemokine receptor antagonism as an approach to anti-inflammatory therapy: 'just right' or plain wrong?

Inflammation plays a pivotal role in exacerbating a wide array of human diseases. The chemokines are a group of proteins that control the movement and activation of the immune cells involved in all aspects of the inflammatory response. Recently, their cognate receptors have attracted considerable interest as therapeutic targets, in part because they are G-protein-coupled receptors, which have been antagonized successfully before by the pharmaceutical industry. Indeed, several companies have now reported the development of selective small-molecule chemokine receptor antagonists, and some of these compounds have even entered human Phase I clinical trials. Preclinical studies of the responsiveness of murine models of inflammation to either pharmacologic or genetic intervention have suggested that antagonism of some chemokine receptors may well prove to be a safe and efficacious approach to anti-inflammatory therapy.

Opposite regulation of type II and III receptors for immunoglobulin G in mouse glomerular mesangial cells and in the induction of anti-glomerular basement membrane (GBM) nephritis

We examined the capacity of mouse glomerular mesangial cells (MC) to express and function through two different low affinity FcgammaRs, the activating FcgammaRIII and the inhibitory FcgammaRII. Immunohistochemistry identified FcgammaRII as the prominent FcgammaR in the kidney, and low levels of FcgammaRIIb2-specific mRNA were also detected in primary cultures of growth-arrested MC. Activation by tumor necrosis factor-alpha/interleukin-1beta induced substantial FcgammaRII expression in proliferating MC. Importantly, however, stimulation with interferon-gamma (IFN-gamma)/lipopolysaccharide or IFN-gamma alone resulted in a complete down-regulation of FcgammaRII, which was accompanied by a strong increase in FcRgamma chain mRNA and a surface appearance of FcgammaRIII. Activating FcgammaRIII triggered mRNA synthesis for monocyte chemoattractant protein-1 (MCP-1), MCP-5, cytokine-induced neutrophil chemoattractant, and RANTES, whereas FcgammaRIII-deficient MC failed to respond to immune complex (IC) activation as shown by impaired production of MCP-1 mRNA/protein. In a passive model of acute anti-glomerular basement membrane (GBM) nephritis, induction of FcgammaRIII and suppression of FcgammaRII occurred in kidney tissues. Blockade of FcgammaRII, when induced selectively in the kidney, resulted in enhanced inflammation. Taken together, our results define a novel regulatory pathway with opposite regulation of FcgammaRII (suppressed) and FcgammaRIII (induced) by IFN-gamma on MCs in vitro and anti-GBM IgG in vivo. Herein is provided the first evidence that glomerular FcgammaRII plays an important immunoregulatory role in the initiation of IC glomerulonephritis.

Transferrin up-regulates chemokine synthesis by human proximal tubular epithelial cells: implication on mechanism of tubuloglomerular communication in glomerulopathic proteinura

BACKGROUND

The pathogenesis of glomerulosclerosis and tubulointerstitial fibrosis in proteinuric renal disease is obscure. We recently showed that transferrin, a key proteinuric component, mediates proximal tubular epithelial cell (PTEC) C3 synthesis. To further examine whether proteinuric tubular injury may induce glomerular inflammation and to characterize the role of transferrin in activating PTEC, glomerular mesangial cells (MC) were exposed to transferrin-activated PTEC culture supernatant and their proliferative and profibrotic responses analyzed.

METHODS

Human PTEC and MC were obtained by primary culture. Confluent, transferrin-stimulated PTEC were grown in serum-free medium to produce a "conditioned" medium that was incubated with quiescent MC. The proliferative response of MC was then assessed by thymidine uptake, and the expression of fibrogenic factors measured by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The chemokine profile in PTEC after transferrin treatment was examined by RT-PCR and ELISA.

RESULTS

"Conditioned" supernatant from PTEC, which contained the highest amounts of platelet-derived growth factor (PDGF), stimulated MC proliferation compared with serum-free (P = 0.03) or transferrin-containing (P = 0.009) control media. This proliferative response was partially abrogated by treating MC with anti-PDGF. MC expression of PDGF, but not transforming growth factor-beta or intercellular cell adhesion molecule-1, was up-regulated by conditioned PTEC medium. Transferrin up-regulated monocyte chemoattractant peptide-1, interleukin-8, and macrophage migration inhibitory factor expression in a time- and dose-dependent fashion, but had no effect on RANTES expression by PTEC.

CONCLUSIONS

These results provide experimental evidence suggesting that there is a tubuloglomerular "cross-talk" mechanism in the proteinuric state. PTEC-secreted PDGF, which further induces mesangial PDGF, could partially account for the mesangial proliferation frequently observed in proteinuric renal disease. Transferrin is one of the culprit nephrotic proteins leading to tubular overexpression of various proinflammatory chemokines, which may explain the interstitial changes observed in proteinuric states.

Expression of cytokine- and chemokine-related genes in peripheral blood mononuclear cells from lupus patients by cDNA array

Systemic lupus erythematosus (SLE) is characterized by diverse and complex immune abnormalities. In an effort to begin to characterize the full complexity of immune abnormalities, the expression pattern of 375 potentially relevant genes was analyzed using peripheral blood mononuclear cells (PBMC) from 21 SLE patients and 12 controls by cDNA arrays. When mean gene expression for patients was compared to controls, 50 genes were identified that exhibited more than 2.5-fold difference in expression level. By the Mann-Whitney U test, 20 genes were significantly different (P < 0.05) between patients and controls. Most of these genes have not been previously associated with SLE and belong to a variety of families such as TNF/death receptor, IL-1 cytokine family, and IL-8 and its receptors. Hierarchical clustering of samples and differentially expressed genes revealed that with few exceptions, patients clustered separately from controls. These results highlight the potential use of the microarray data in identifying genes associated with SLE, which could become candidate molecular markers or future therapeutic targets.

Combined modulation of the mesangial machinery for monocyte recruitment by inhibition of NF-kappaB

The activation of nuclear factor-kappaB (NF-kappaB) is required for the induction of many of the adhesion molecules and chemokines involved in the inflammatory leukocyte recruitment to the kidney. Here we studied the effects of NF-kappaB inhibition on the machinery crucial for monocyte infiltration of the glomerulus during inflammation. In mesangial cells (MC), the protease inhibitors MG-132 and N-alpha-tosyl-L-lysine chloromethyl ketone or adenoviral overexpression of IkappaB-alpha prevented the complete IkappaB-alpha degradation following tumor necrosis factor-alpha (TNF-alpha) stimulation. This resulted in a marked inhibition of TNF-alpha-induced expression of mRNA and protein for the immunoglobulin molecules intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 and the chemokines growth-related oncogene-alpha, monocyte chemoattractant protein-1, interleukin-8, or fractalkine in MC. Finally, the inhibition of IkappaB-alpha degradation or IkappaB-alpha overexpression suppressed the chemokine-induced transendothelial monocyte chemotaxis toward MC and the chemokine-triggered firm adhesion of monocytic cells to MC. The inhibition of NF-kappaB by pharmacological intervention or gene transfer may present a multimodal approach to control the machinery propagating inflammatory recruitment of monocytes during glomerular disease.