Search PubMed⌕ Search

Biomedical subjects

Richard J Quigg

Publications and source records attributed to Richard J Quigg.

At least 19 recordsLinked to original sources
PubMed2005

Signaling through up-regulated C3a receptor is key to the development of experimental lupus nephritis.

Signaling of the C3a anaphylatoxin through its G protein-coupled receptor, C3aR, is relevant in a variety of inflammatory diseases, but its role in lupus nephritis is undefined. In this study, we show that expression of C3aR was significantly increased in prediseased and diseased kidneys of MRL/lpr lupus mice compared with MRL/+ controls. To investigate the role of C3aR in experimental lupus, a small molecule antagonist of C3aR (C3aRa) was administered continuously to MRL/lpr mice from 13 to 19 wk of age. All 13 C3aRa-treated mice survived during the 6-wk treatment compared with 9 of 14 (64.3%) control animals given vehicle (p = 0.019). Relative to controls, C3aRa-treated animals were protected from renal disease as measured by albuminuria (p = 0.040) and blood urea nitrogen (p = 0.021). In addition, there were fewer neutrophils, monocytes, and apoptotic cells in the kidneys of C3aRa-treated mice. C3aRa treatment also led to reduced renal IL-1beta and RANTES mRNA and phosphorylated phosphatase and tensin homologue deleted on chromosome 10 protein, whereas the mass of phosphorylated protein kinase B/Akt was increased by C3aRa. Thus, C3aR antagonism significantly reduces renal disease in MRL/lpr mice, which further translates into prolonged survival. These data illustrate that C3aR is relevant in experimental lupus nephritis and may be a target for therapeutic intervention in the human disease.

Animals↗
PubMed2005

Early signals for fracture healing.

Fracture healing requires the cooperation of multiple molecular signaling pathways. To better understand this cascade of transcriptional events, we compared the gene expression profiles between intact bone and fractured bone at days 1, 2, and 4 using a rat femur model of bone healing. Cluster analysis identified several groups of genes with dynamic temporal expression patterns and stage-specific functions. The immediate-response genes are highlighted by binding activity, transporter activity, and energy derivation. We consider these activities as critical signals for initiation of fracture healing. The continuously increased genes are characterized by those directly involved in bone repair, thus, representing bone specific forefront workers. The constantly upregulated genes tend to regulate general cell growth and are enriched with genes that are involved in tumorigenesis, suggesting common pathways between two processes. The constantly downregulated genes predominantly involve immune response, the significance of which remains for further investigation. Knowledge acquired through this analysis of transcriptional activities at the early stage of bone healing will contribute to our understanding of fracture repair and bone-related pathological conditions.

Animals↗
PubMed2005

Complement inhibitors targeted to the proximal tubule prevent injury in experimental nephrotic syndrome and demonstrate a key role for C5b-9.

In glomerular diseases of diverse etiologies, dysfunction of the glomerular barrier to protein passage results in proteinuria, and proteinuria is considered an independent risk factor that plays a direct role in inflammation, interstitial fibrosis, and renal failure. The mechanism by which proteinuria leads to nephrotoxic injury is unclear, but a role for complement in mediating interstitial damage appears likely. We describe a strategy for Ag-specific targeting of complement inhibitors using a single chain Ab fragment and show that complement inhibitors targeted to the tubular epithelium protect against tubulointerstitial injury and renal dysfunction in a rat model of puromycin-induced nephrosis. The targeting of systemically administered complement inhibitors markedly enhanced their efficacy and obviated the need to systemically inhibit complement, thus reducing the risk of compromising host defense and immune homeostasis. Targeted inhibition of complement activation by Crry, and of membrane attack complex (MAC) formation by CD59 was equally therapeutic, demonstrating that the MAC plays a key role in proteinuria-induced tubulointerstitial injury. CD59 activity was dependent on its being targeted to the site of complement activation, and this is the first report of specific inhibition of the MAC in vivo after systemic administration of inhibitor. The data establish the MAC is a valid target for pharmaceutical intervention in proteinuric disorders and provide an approach to investigate the role of the MAC in complement-dependent disease under clinically relevant conditions.

Animals↗
PubMed2005

Contrasting roles of complement activation and its regulation in membranous nephropathy.

The complement system is involved in defense against microorganisms, the processing of immune complexes and apoptotic debris, and the development of an appropriate immune response. Along with these physiologic effects, complement activation has the potential to result in tissue pathology. To limit this, various complement regulatory proteins (CRP) are present on host cells, including the glomerular podocyte. Experimental data from the Heymann nephritis (HN) rat model of human membranous nephropathy (MN) have shown that IgG antibodies in subepithelial immune deposits initiate complement activation and C5b-9-mediated damage of the overlying podocyte. Although IgG can activate the classical pathway, there also is evidence that alternative pathway activation occurs in MN, which could occur because of absent, dysfunctional, or inhibited podocyte CRP. Related to this are experimental data in HN showing the presence of antibodies that bind and inhibit podocyte CRP; although such antibodies have not been documented in human MN, a decrease in CR1 quantity on the podocyte has been observed. A s a result of a relative lack of CRP and the exposure of activating complement proteins to tubular cells, alternative complement pathway activation and C5b-9-mediated tubular injury can occur in MN and other proteinuric diseases. Overall, in a disease such as MN, the balance between complement regulation and activation is tipped toward its being activated. Therefore, a number of therapeutic approaches have been developed to counteract this, including recombinant forms of endogenous CRP and complement-inhibitory monoclonal antibodies. There is good reason to be optimistic that approaches to block complement activation will become viable therapy for human MN in the future.

Animals↗
PubMed2005

C5a promotes development of experimental lupus nephritis which can be blocked with a specific receptor antagonist.

The MRL/lpr murine SLE model has widespread complement activation and deposition of complement fragments in affected tissues. The potent anaphylatoxin C5a has the potential to play a key role in the pathogenesis of lupus nephritis. We found that renal expression of C5aR mRNA and protein was significantly increased in MRL/lpr mice compared to control MRL/+ mice. To examine the role of C5a signaling through C5aR, a specific small molecule antagonist (a) of C5aR was administered continuously to MRL/lpr mice from 13 to 19 wks of age. Littermate controls were given vehicle alone. The progressive impairment in renal function exhibited in the control group was prevented by C5aRa treatment. Infiltration of neutrophils and macrophages into kidneys was significantly reduced in animals treated with C5aRa compared to controls. Furthermore, renal expression of IL-1beta and MIP-2 mRNA as well as the extent of apoptosis were significantly decreased with blockade of C5aR, indicating their dependence upon signals delivered through C5aR. Thus, pharmacological blockade of C5aR reduces disease manifestations in experimental lupus nephritis. These data support an important role for the C5a anaphylatoxin in lupus nephritis, and that blockade of C5aR represents a potentially viable treatment for human lupus nephritis.

Age Factors↗
PubMed2005

Treatment of glomerulonephritis: will we ever have options other than steroids and cytotoxics?

Glomerulonephritis refers to a collection of primary renal disorders and those secondary to a systemic disease, all characterized by inflammation within the glomerulus. Given the underlying immunologic nature of these disorders, they are routinely treated with corticosteriods and various cytotoxic agents. Although in many instances such therapies are successful, they are associated with significant morbidity; as such, alternatives are clearly necessary. Our understanding of the pathogenesis of immunologic glomerular diseases has grown remarkably, in large part from the study of rodent disease models. Fundamental to each disorder is the development of an antigen-specific immune response followed by the effector stage of inflammation. To block the immune response, antigen-specific therapy can be used to induce tolerance, such as through the use of double-stranded DNA molecules in lupus nephritis. Since other antigen systems are less well characterized, inducing a more generalized impairment in the immune response by blocking costimulatory molecules CD40-CD154 and CD28-CD80/86 is a growing approach to treat various immunologic disorders and transplantation. To reduce glomerular inflammation, a variety of effector systems have been targeted, including complement, cytokines/chemokines, adhesion molecules, and mediators of cellular proliferation. Of these, antibodies targeting C5 in the complement system, and antibody and receptor antagonists of tumor necrosis factor-alpha (TNF-alpha) have already been used in glomerular disorders with some promise. Less specific blockade of receptor-mediated events stimulated by platelet-derived growth factors and cell cycle proteins may soon be applied to glomerulonephritis. Finally, interruption of fibrosing pathways, which lead to glomerulosclerosis and interstitial fibrosis common to the end-stage of all glomerulonephritis, is the subject of intense effort which may yield effective biologic therapies. In spite of all these advances, we still are dependent on steroids and cytotoxics to treat glomerulonephritis. To get past this, we must devote significant resources to take observations made in basic research laboratories to develop therapeutics and prove their utility in human disease.

Adrenal Cortex Hormones↗
PubMed2004

Complement factor h limits immune complex deposition and prevents inflammation and scarring in glomeruli of mice with chronic serum sickness.

Factor H is the major complement regulator in plasma. Abnormalities in factor H have been implicated in membranoproliferative glomerulonephritis in both humans and experimental animals. It has been shown that factor H on rodent platelets functions analogously to human erythrocyte complement receptor 1 in its role to traffic immune complexes to the mononuclear phagocyte system. C57BL/6 factor H-deficient mice (Cfh(-/-)) and wild-type (wt) controls were immunized daily for 5 wk with heterologous apoferritin to study the chronic serum sickness GN model. Immunizations were started in 6- to 8-wk-old mice, which was before the development of spontaneous membranoproliferative glomerulonephritis in some Cfh(-/-) animals. Glomerular deposition of IgG immune complexes in glomeruli was qualitatively and quantitatively increased in Cfh(-/-) mice compared with wt mice. Consistent with the increase in glomerular immune complexes and possibly because of alternative pathway complement activation, Cfh(-/-) mice had increased glomerular C3 deposition. Wt mice developed no glomerular pathology. In contrast, Cfh(-/-) mice developed diffuse proliferative GN with focal crescents and glomerulosclerosis. In addition, there was significantly increased expression of collagen IV, fibronectin, and laminin mRNA in Cfh(-/-) glomeruli. These data show a role for platelet-associated factor H to process immune complexes and limit their accumulation in glomeruli. Once deposited in glomeruli, excessive complement activation can lead to glomerular inflammation and the rapid development of a scarring phenotype.

Animals↗
PubMed2004

Role of Toll-like receptor 4 in endotoxin-induced acute renal failure.

Toll-like receptor 4 (TLR4) is present on monocytes and other cell types, and mediates inflammatory events such as the release of TNF after exposure to LPS. C3H/HeJ mice are resistant to LPS-induced mortality, due to a naturally occurring mutation in TLR4. We therefore hypothesized that LPS-induced acute renal failure (ARF) requires systemic TNF release triggered by LPS acting on extrarenal TLR4. We injected C3H/HeJ mice and C3H/HeOuJ controls with 0.25 mg of LPS, and sacrificed them 6 h later for analysis of blood urea nitrogen (BUN) and kidney tissue (n = 8 per group). In contrast to C3H/HeOuJ controls, C3H/HeJ mice were completely resistant to LPS-induced ARF (6-h BUN of 32.3 +/- 1.1 vs 61.7 +/- 5.6 mg/dl). C3H/HeJ mice released no TNF into the circulation at 2 h (0.00 vs 1.24 +/- 0.16 ng/ml), had less renal neutrophil infiltration (6.4 +/- 1.0 vs 11.4 +/- 1.3 neutrophils per high power field), and less renal apoptosis, as assessed by DNA laddering. Transplant studies showed that C3H/HeJ recipients of wild-type kidneys (n = 9) were protected from LPS-induced ARF, while wild-type recipients of C3H/HeJ kidneys (n = 11) developed severe LPS-induced ARF (24-h BUN 44.0 +/- 4.1 vs 112.1 +/- 20.0 mg/dl). These experiments support our hypothesis that LPS acts on extrarenal TLR4, thereby leading to systemic TNF release and subsequent ARF. Renal neutrophil infiltration and renal cell apoptosis are potential mechanisms by which endotoxemia leads to functional ARF.

ADP-Ribosylation Factor 6↗
PubMed2004

CR1/CR2 deficiency alters IgG3 autoantibody production and IgA glomerular deposition in the MRL/lpr model of SLE.

CR1 and CR2 expression is decreased by approximately 50% on B cells of patients with systemic lupus erythematosus (SLE). Expression is also decreased in the MRL/lpr murine model of SLE prior to the development of clinical disease, suggesting that this alteration may play a role in pathogenesis. To determine whether the decrease in receptor levels affects the development of SLE, we analyzed MRL/lpr mice in which CR1/CR2 expression was altered by gene targeting. Mice from each cohort (Cr2+/+, Cr2+/-, and Cr2-/-) were analyzed biweekly for the development of proteinuria and autoantibodies. Kidneys were examined at 12 and 16 weeks for evidence of immune complex deposition and renal disease. Deficiency of CR1/CR2 did not affect survival or development of renal disease as measured by proteinuria. Mice deficient in CR1/CR2 had significantly lower levels of IgG3 rheumatoid factor (RF) and total serum IgG3, suggesting a specific defect in production of IgG3 in response to endogenous autoantigens. Since IgG3 RF has been associated with the development of vasculitis in this model, we examined the mice for alterations in development of this clinical manifestation. Although there was no difference in the development of ear necrosis among the three groups, renal arteritis was not identified in any of the Cr2+/- mice, whereas it was present in 20% of the Cr2+/- and 40% of the Cr2+/+ mice. Finally, significantly higher levels of IgA were seen in the glomeruli of Cr2+/- mice compared to Cr2+/- or Cr2+/+ mice, suggesting that CR1/CR2 are involved in either the regulation of IgA production or the clearance of IgA immune complexes. Together these data support the concept that alterations in CR1/CR2 expression or function affect the regulation of autoantibody production and/or clearance and may have clinical consequences.

Animals↗
PubMed2004

Acute renal failure in endotoxemia is dependent on caspase activation.

In previous work, it was demonstrated that apoptosis occurs in the kidney during LPS-induced acute renal failure (ARF). However, the relative importance of apoptosis in LPS-induced ARF remained unproven. Because the caspase enzyme cascade is responsible for carrying out apoptosis, it was hypothesized that treatment with a caspase inhibitor would protect mice from LPS-induced ARF. C57BL/6 mice received an injection of LPS and were treated with either the broad-spectrum caspase inhibitor z-VAD-fmk or vehicle and compared with unmanipulated mice. LPS induced a significant increase in caspase-3 activity in vehicle-treated mice, which was significantly inhibited by z-VAD. Mice that were treated with z-VAD were protected from ARF and demonstrated significantly less apoptosis as measured by both terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining and DNA laddering. Although apoptosis is classically described as a noninflammatory process, z-VAD treatment significantly attenuated multiple markers of inflammation, such as renal neutrophil infiltration and renal expression of the neutrophil chemotactic factor macrophage inflammatory protein-2. Thus, caspase inhibition may protect against LPS-induced ARF not only by preventing apoptotic cell death but also by inhibiting inflammation. These data raise the possibility that apoptotic kidney cells may actually be a source of this local inflammation, contributing to subsequent nonapoptotic renal injury.

Acute Kidney Injury↗
PubMed2004

Overexpression of complement inhibitor Crry does not prevent cryoglobulin-associated membranoproliferative glomerulonephritis.

BACKGROUND: Mice overexpressing thymic stromal lymphopoietin (TSLP) develop mixed cryoglobulinemia with renal disease closely resembling human cryoglobulin-associated membranoproliferative glomerulonephritis (MPGN), including glomerular deposits of immunoglobulins and complement. We assessed the effect of complement inhibition through overexpression of Crry (complement receptor-1 related gene/protein Y), which blocks the classic and alternative pathway of complement activation through inhibition of the C3 convertase, in cryoglobulinemia-associated immune complex glomerulonephritis. METHODS: TSLP transgenic mice were crossbred with animals overexpressing Crry. Mice were sacrificed after 50 days (females) or 120 days (males), and kidneys, blood, and urine were collected from seven mice of each experimental group (wild type, Crry transgenic, TSLP transgenic, and Crry/TSLP doubly transgenic). RESULTS: TSLP/Crry doubly transgenic animals demonstrated expected serum levels of Crry. Renal involvement, both in TSLP transgenic and TSLP/Crry doubly transgenic animals, was characterized by glomerular matrix expansion, macrophage influx, activation of mesangial cells, and deposition of immunoglobulins and complement. Overexpression of Crry did not result in significant improvement of renal pathology or laboratory findings. Expression of recombinant soluble Crry was confirmed by enzyme-linked immunosorbent assay (ELISA) in Crry transgenic animals. However, formation of the membrane attack complex C5b-9 as a marker of terminal active complement components and represented by glomerular C9 staining could not be inhibited in Crry transgenic TSLP mice. CONCLUSION: These results indicate that overexpression of Crry was not sufficient to prevent renal injury in TSLP transgenic mice. We suggest that the inhibitory capacity of Crry may be overwhelmed by chronic complement activation. Further studies need to address the role of complement in cryoglobulinemic glomerulonephritis before therapeutic complement inhibition can be attempted.

Animals↗
PubMed2004

Complement and autoimmune glomerular diseases.

The renal glomerulus is the specialized structure in the kidney responsible for generating over 150 liters of plasma ultrafiltrate per day in humans. Certain characteristics of this structure favor involvement in autoimmune diseases. Formation of immune complexes in the glomerulus, either deposited from the circulation or generated in situ, can activate the complement system. Active products of this system include the anaphylatoxins C3a and C5a, C3b, which covalently associates with immune complexes, and the C5b-9 membrane attack complex. If complement is activated in a site accessible to blood constituents, such as in the subendothelial and mesangial regions, generated C3a, C5a and C3b can interact with their respective receptors on inflammatory cells to lead to an exudative lesion. In addition, intrinsic glomerular cells bearing relevant receptors may also be activated and can proliferate to contribute to the inflammation. In a privileged site such as the subepithelial region, complement activation products are not accessible to blood cells, and as such, the resultant pathology is noninflammatory. In this setting, effects of C5b-9 predominate, which include activation and injury of cells through still incompletely characterized pathways. Various means to alter the complement pathway are now available, including antibody inhibitors and recombinant proteins based upon naturally occurring complement regulators. The use of these agents, as well as mice in which individual components of the complement system have been deleted, has given a great deal of insight into how the complement system is involved in glomerular disease. The ability to manipulate the complement pathway is now a reality in a clinical setting, yet conclusive human studies are difficult to achieve.

Animals↗
PubMed2004

Selective expression of TGF-beta2 and TGF-beta3 isoforms in early mesangioproliferative glomerulonephritis.

BACKGROUND/AIM: Evidence from ex vivo glomerular analysis has implicated overexpression of transforming growth factor (TGF) beta 1 in progressive renal disease. The roles of TGF-beta2 and TGF-beta3 are less clear. The purpose of this study was to define the temporal expression and abundance of TGF-beta isoforms in both acute and progressive Thy-1 glomerulonephritis during the crucial initiation phase of these models. METHODS: Acute Thy-1 glomerulonephritis was induced by a single injection of OX7, while the progressive model was induced by two injections, 7 days apart. RESULTS: Cellular infiltration of glomeruli consisted of transient increases of neutrophils and ED1+ macrophages. The distribution of TGF-beta1, TGF-beta2, and TGF-beta3 revealed distinct differences in normal and nephritic rats. No changes in TGF-beta1 staining were observed within glomeruli of either model. In marked contrast, in the one-shot model, TGF-beta2 and TGF-beta3 stainings increased rapidly, yet transiently, throughout affected glomeruli, followed by more sustained staining in glomerular epithelial cells. Diffuse, transient staining was absent in two-shot glomerulonephritis, but an increase in epithelial cell staining mirrored that seen in the one-shot model. CONCLUSION: Based on these results, we propose that the effects, formerly thought of as solely due to a single entity, TGF-beta1, may be the result of an interplay between individual TGF-beta isoforms.

Acute Disease↗
PubMed2003

Administration of the soluble complement inhibitor, Crry-Ig, reduces inflammation and aquaporin 4 expression in lupus cerebritis.

Changes in brain water and cerebral volume can lead to brain edema that may be one of the underlying causes of death in many neurological diseases. Cerebral water content is regulated by aquaporin 4 (AQ4) present in astrocytic end feet and around blood vessels. In systemic lupus erythematosus (SLE), magnetic resonance imaging (MRI) studies of the brain have demonstrated lesions with the prominent appearance of edema. Activation of complement may play a significant role in the pathogenesis of lupus cerebritis by causing inflammation that can lead to edema. In this study, the well-established MRL/lpr lupus mouse model was used to evaluate the role of complement in lupus cerebritis. IgG and C1q colocalized in perivascular deposits indicating that the blood-brain barrier was compromised. Both RNA and protein expressions of AQ4 were significantly increased in brains of MRL/lpr mice. Chronic administration of the soluble complement inhibitor, Crry-Ig, reduced inflammation as measured by decreased accumulation of IgG. In contrast to control MRL/lpr mice, AQ4 expression in complement inhibited MRL/lpr mice was not changed relative to untreated congenic controls. These results illustrate that complement activation in brains of lupus mice leads to enhanced AQ4 expression and inflammation. It is conceivable that increased AQ4 expression results in cerebral edema and hence complement inhibition may provide a new therapeutic option in inflammatory cerebral disorders such as lupus cerebritis.

Animals↗
PubMed2003

The extended multidomain solution structures of the complement protein Crry and its chimeric conjugate Crry-Ig by scattering, analytical ultracentrifugation and constrained modelling: implications for function and therapy.

Complement receptor-related gene/protein y (Crry) is a cell membrane-bound regulator of complement activation found in mouse and rat. Crry contains only short complement/consensus repeat (SCR) domains. X-ray and neutron scattering was performed on recombinant rat Crry containing the first five SCR domains (rCrry) and mouse Crry with five SCR domains conjugated to the Fc fragment of mouse IgG1 (mCrry-Ig) in order to determine their solution structures at medium resolution. The radius of gyration R(G) of rCrry was determined to be 4.9-5.0 nm, and the R(G) of the cross-section was 1.2-1.5 nm as determined by X-ray and neutron scattering. The R(G) of mCrry-Ig was 6.6-6.7 nm, and the R(G) of the cross-section were 2.3-2.4 nm and 1.3 nm. The maximum dimension of rCrry was 18 nm and that for mCrry-Ig was 26 nm. The neutron data indicated that rCrry and mCrry-Ig have molecular mass values of 45,000 Da and 140,000 Da, respectively, in agreement with their sequences, and sedimentation equilibrium data supported these determinations. Time-derivative velocity experiments gave sedimentation coefficients of 2.4S for rCrry and 5.4S for mCrry-Ig. A medium-resolution model of rCrry was determined using homology models that were constructed for the first five SCR domains of Crry from known crystal and NMR structures, and linked by randomly generated linker peptide conformations. These trial-and-error calculations revealed a small family of extended rCrry structures that best accounted for the scattering and ultracentrifugation data. These were shorter than the most extended rCrry models as the result of minor bends in the inter-SCR orientations. The mCrry-Ig solution data were modelled starting from a fixed structure for rCrry and the crystal structure of mouse IgG1, and was based on conformational searches of the hinge peptide joining the mCrry and Fc fragments. The best-fit models showed that the two mCrry antennae in mCrry-Ig were extended from the Fc fragment. No preferred orientation of the antennae was identified, and this indicated that the accessibility of the antennae for the molecular targets C4b and C3b was not affected by the covalent link to Fc. A structural comparison between Crry and complement receptor type 1 indicated that the domain arrangement of Crry SCR 1-3 is as extended as that of the CR1 SCR 15-17 NMR structure.

Amino Acid Sequence↗
PubMed2003

cDNA microarray analysis of macroregenerative and dysplastic nodules in end-stage hepatitis C virus-induced cirrhosis.

Hepatocellular carcinoma is a common malignancy causing significant morbidity and mortality worldwide. In this study we use expression microarray technology to identify novel genes that consistently displayed altered expression levels in the earliest identifiable precursors to hepatocellular carcinoma, dysplastic and macroregenerative nodules. The gene expression profiles from nine patients with end-stage hepatitis C cirrhosis that contained a combined 11 dysplastic or macroregenerative nodules were compared to the patient's matched cirrhotic liver tissue. A total of 53 genes were consistently dysregulated in the patient liver specimens. Six of seven genes were validated by quantitative real-time reverse transcriptase-polymerase chain reaction, or by immunohistochemical studies performed on an independent set of lesions. The novel genes, including caveolin-1, semaphorin E, and FMS-like tyrosine kinase 3 ligand, have putative roles in carcinogenesis but have not been reported in hepatocellular carcinogenesis. Microarray expression analysis of dysplastic and macroregenerative liver nodules provide insight into the earliest changes in hepatocellular carcinogenesis.

Base Sequence↗