Autoimmunity and inflammation are independent of class II transactivator type PIV-dependent class II major histocompatibility complex expression in peripheral tissues during collagen-induced arthritis

OBJECTIVE

To determine the regulation of class II major histocompatibility complex (MHC) expression in fibroblast-like synoviocytes (FLS) in order to investigate their role as nonprofessional antigen-presenting cells in collagen-induced arthritis (CIA).

METHODS

Expression of class II MHC, class II MHC transactivator (CIITA), and Ciita isoforms PI, PIII, and PIV was examined by real-time quantitative polymerase chain reaction, immunohistochemistry, and flow cytometry in human synovial tissues, arthritic mouse joints, and human and murine FLS. CIA was induced in mice in which isoform PIV of Ciita was knocked out (PIV(-/-) ), in PIV(-/-) mice transgenic for CIITA in the thymus (K14 CIITA), and in their control littermates.

RESULTS

HLA-DRA, total CIITA, and CIITA PIII messenger RNA levels were significantly increased in synovial tissue samples from patients with rheumatoid arthritis compared with the levels in tissue from patients with osteoarthritis. Human FLS expressed surface class II MHC via CIITA PIII and PIV, while class II MHC expression in murine FLS was entirely mediated by PIV. Mice with a targeted deletion of CIITA PIV lack CD4+ T cells and were protected against CIA. The expression of CIITA was restored in the thymus of PIV(-/-) K14 CIITA-transgenic mice, which had a normal CD4+ T cell repertoire and normal surface levels of class II MHC on professional antigen-presenting cells, but did not induce class II MHC on FLS. Synovial inflammation and immune responses against type II collagen were similar in PIV(-/-) K14 CIITA-transgenic mice and control mice with CIA, but bone erosion was significantly reduced in the absence of PIV.

CONCLUSION

Overexpression of class II MHC is tightly correlated with CIITA expression in arthritic synovium and in FLS. Selective targeting of Ciita PIV in peripheral tissues abrogates class II MHC expression by murine FLS but does not protect against inflammation and autoimmune responses in CIA.

Protein level expression of Toll-like receptors 2, 4 and 9 in renal disease

BACKGROUND

Toll-like receptors (TLR) recognize a variety of ligands, including pathogen-associated molecular patterns and link innate and adaptive immunity. Individual receptors can be up-regulated during infection and inflammation. We examined the expression of selected TLRs at the protein level in various types of renal disease.

METHODS

Frozen sections of renal biopsies were stained with monoclonal antibodies to TLR-2, -4 and -9.

RESULTS

Up-regulation of the three TLRs studied was seen, although the extent was modest. TLR-2- and -4-positive cells belonged to the population of infiltrating inflammatory cells; only in the case of TLR-9 were intrinsic glomerular cells positive in polyoma virus infection and haemolytic uraemic syndrome (HUS).

CONCLUSIONS

Evidence for the involvement of the three TLRs tested in a variety of human renal diseases was found. These findings add to our understanding of the role of the innate immune system in kidney disease.

Expression of cathepsin K and matrix metalloproteinase 1 indicate persistent osteodestructive activity in long-standing ankylosing spondylitis

BACKGROUND

Ankylosing spondylitis (AS) is a common, largely genetically determined, rheumatic disease that is characterised by spinal inflammation and new bone formation. However, the exact pathogenesis and pathology are still not clear.

OBJECTIVE

To analyse tissue obtained at spinal surgery by immunohistochemistry and compare the specimen of patients with AS to those with degenerative disc disease (DDD).

METHODS

Bony and soft tissue specimens of 30 patients with AS and 20 with DDD were obtained during spinal osteotomy from different anatomic regions including articular and spinous processes, interspinous ligaments and intervertebral disks. Immunohistolochemistry was performed with established markers for cathepsin K, matrix metalloproteinase (MMP)1, MMP3 and receptor activator for nuclear factor kappaB (RANK) ligand.

RESULTS

Cathepsin K and MMP1-positive cells were only observed in AS specimens. Cathepsin K-positive multinucleated cells were detected at articular processes adjacent to fibrous tissues. MMP1 was expressed in smaller mononuclear cells attached to bone. Invasion of bone by MMP1 cells was seen at entheseal sites. In the intervertebral disks, most mononuclear cells were cathepsin K-positive. Isolated cells expressing these matrix-degrading enzymes found in DDD never showed signs of invasion. No differences were found for MMP3 between AS and DDD. Clear expression of RANK ligand was only detected in one patient with AS.

CONCLUSIONS

Cathepsin K is strongly expressed in different regions of the spine in AS. Cathepsin K was mainly expressed by mononuclear cells, fibroblast-like cells and cells attached to bone and at sites of bone remodelling, suggestive of high osteoclastic activity. This supports the role of persistent inflammation in the pathogenesis of AS. How these changes relate to osteoproliferation remains to be determined.

[Lys40(Ahx-DTPA-111In)NH2]-Exendin-4 is a highly efficient radiotherapeutic for glucagon-like peptide-1 receptor-targeted therapy for insulinoma

PURPOSE

Although metabolic changes make diagnosis of insulinoma relatively easy, surgical removal is hampered by difficulties in locating it, and there is no efficient treatment for malignant insulinoma. We have previously shown that the high density of glucagon-like peptide-1 receptors (GLP-1R) in human insulinoma cells provides an attractive target for molecular imaging and internal radiotherapy. In this study, we investigated the therapeutic potential of [Lys(40)(Ahx-DTPA-(111)In)NH(2)]-Exendin-4, an (111)In-labeled agonist of GLP-1, in a transgenic mouse model of human insulinoma.

EXPERIMENTAL DESIGN

[Lys(40)(Ahx-DTPA-(111)In)NH(2)]-Exendin-4 was assessed in the Rip1Tag2 mouse model of pancreatic beta-cell carcinogenesis, which exhibits a GLP-1R expression comparable with human insulinoma. Mice were injected with 1.1, 5.6, or 28 MBq of the radiopeptide and sacrificed 7 days after injection. Tumor uptake and response, the mechanism of action of the radiopeptide, and therapy toxicity were investigated.

RESULTS

Tumor uptake was >200% injected activity per gram, with a dose deposition of 3 Gy/MBq at 40 pmol [Lys(40)(Ahx-DTPA-(111)In)NH(2)]-Exendin-4. Other GLP-1R-positive organs showed > or =30 times lower dose deposition. A single injection of [Lys(40)(Ahx-DTPA-(111)In)NH(2)]-Exendin-4 resulted in a reduction of the tumor volume by up to 94% in a dose-dependent manner without significant acute organ toxicity. The therapeutic effect was due to increased tumor cell apoptosis and necrosis and decreased proliferation.

CONCLUSIONS

The results suggest that [Lys(40)(Ahx-DTPA-(111)In)NH(2)]-Exendin-4 is a promising radiopeptide capable of selectively targeting insulinoma. Furthermore, Auger-emitting radiopharmaceuticals such as (111)In are able to produce a marked therapeutic effect if a high tumor uptake is achieved.

Detection of synovial macrophages in an experimental rabbit model of antigen-induced arthritis: ultrasmall superparamagnetic iron oxide-enhanced MR imaging

PURPOSE

To evaluate intravenously administered ultrasmall superparamagnetic iron oxide (USPIO) as a marker of macrophage activity in an experimental rabbit model of antigen-induced arthritis.

MATERIALS AND METHODS

Unilateral arthritis was induced by means of intraarticular injection of methylated bovine serum albumin in 10 knees of 10 rabbits that had been presensitized to the same antigen. The contralateral knees in these rabbits, as well as six knees in three other rabbits, served as controls. After onset of arthritis, all knees were imaged prior to and 24 hours after administration of USPIO. The magnetic resonance (MR) imaging protocol included T1-weighted spin-echo, T2-weighted fast spin-echo, T2*-weighted gradient-echo, and short inversion time inversion-recovery sequences. Images were analyzed quantitatively and qualitatively with regard to signal characteristics and pattern. MR findings were correlated with histopathologic findings. Wilcoxon signed rank test was used to compare results of signal-to-noise ratio calculations before and after USPIO administration.

RESULTS

All knees with intraarticular injection of antigen suspension developed unilateral arthritis, whereas no signs of arthritis occurred in the control knees. On USPIO-enhanced images obtained 24 hours after contrast agent administration, significant T1 (P =.03) and more predominantly T2* (P =.02) and T2 effects (P =.01) were evident in the synovium of all 10 arthritic knees, which reflected USPIO uptake by macrophages in the synovial tissue. To a lesser extent, T2* effects were present also within the joint effusion (P =.01). No significant changes in signal characteristics were detected in the 10 nonarthritic knees in the antigen-injected group or the six knees in the control group (P =.06-.91). Histologic examination confirmed uptake of iron in the macrophages of arthritic knees. Changes in MR signal characteristics within the arthritic synovium and synovial effusion were visually detectable after intravenous administration of USPIO.

CONCLUSION

MR imaging at 1.5 T can depict USPIO uptake in phagocytic-active macrophages in an antigen-induced arthritis animal model.

FLICE-inhibitory protein expression in synovial fibroblasts and at sites of cartilage and bone erosion in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by a hyperplastic synovial tissue, inflammatory infiltrates, and a progressive destruction of cartilage and bone. FLICE-inhibitory protein (FLIP) prevents the association of caspase 8 with FADD and thus exerts an antiapoptotic effect through inhibition of Fas-mediated apoptosis. We undertook this study to examine the expression of FLIP in RA, osteoarthritic (OA), and normal synovial tissues.

METHODS

We investigated the expression of FLIP (long form) in 5 RA, 2 OA, and 2 normal synovial tissue samples. A 393-bp fragment was amplified from complementary DNA obtained from cultured RA synovial fibroblasts (RASF) by reverse transcription-polymerase chain reaction (RT-PCR). Using in situ hybridization, the expression of FLIP messenger RNA (mRNA) in paraffin-embedded synovial tissue sections was investigated semiquantitatively by analyzing the lining layer, the sublining, and sites of invasion. Immunohistochemistry with anti-CD68 antibodies was performed on serial tissue sections to further characterize the cell types expressing FLIP. In addition, quantitative expression of FLIP was measured by real-time PCR.

RESULTS

RT-PCR revealed the expression of FLIP mRNA in all RA and OA samples tested. Using in situ hybridization in synovial tissue, FLIP was detected in all 5 RA samples and in 1 of 2 OA samples, but in neither of the 2 normal control samples. In RA, FLIP expression could be found in both the lining and sublining layers; most importantly, it could also be identified at sites of cartilage invasion and bone destruction. Moreover, quantitative PCR analysis showed 50% higher FLIP expression in RASF than in OASF.

CONCLUSION

The expression of antiapoptotic FLIP in RA synovial tissue and in synovial fibroblasts suggests the idea of a novel pathway in RA that potentially extends the lifespan of cartilage- and bone-degrading synovial cells, thus contributing to the progression of joint destruction.