Ryuichi Saura

The role of cyclooxygenase-2 and inflammatory cytokines in pain induction of herniated lumbar intervertebral disc

Lumbar disc herniation (LDH) is the disease which is the major cause of radiculopathy. In terms of the pathogenesis of disease, it is reported that prostaglandinE2 (PGE2) plays an important role to induce radiculopathy. Arachidonate cascade, which is the process of PGE2 synthesis, is mainly regulated by two kinds of enzymes, phospholipaseA2 (PLA2) and cyclooxy genase (COX). Previously, PLA2 was recognized as the rate-limiting enzyme of this cascade, and some authors reported the clinical significance of PLA2 at the site of LDH concerning the radicular pain. Recently, COX was elucidated to consist of 2 types of isoform, a constitutive form of COX-1 and an inducible form of COX-2. COX-2 has been focused as a key enzyme to regulate PGE2 synthesis and plays an important role in inflammation, because COX-2 was induced in many types of cells by the stimulation of inflammatory cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). However, it is not fully discussed whether or not, COX-2 is induced in lumbar disc tissue and if it plays a significant role in the pathogenesis of LDH. To clarify the role of COX-2 in the pathomechanism of radiculopathy of LDH, we have investigated the expression of COX-2, IL-1 beta and TNF alpha in herniated lumbar disc tissue. Immunohistologically, they were detected in the cytosol of chondrocytes constituting the disc tissue. RT-PCR showed that herniated lumbar disc-derived cells expressed mRNA of COX-2, IL-1 beta and TNF alpha in the presence of inflammatory cytokines in vitro. The disc-derived cells also produced much PGE2 by stimulating of inflammatory cytokines at the same time and this PGE2 production was distinctly suppressed by a selective inhibitor of COX-2, 6-methoxy-2-naphtyl acetic acids (6MNA). These results suggest that COX-2 and inflammatory cytokines might play a causative role in the radiculopathy of LDH through upregulating PGE2 synthesis.

Cytokine enhancement of monocyte/synovial cell attachment to the surface of cartilage: a possible trigger of pannus formation in arthritis

SummaryWhen rheumatoid articular cartilage samples were incubated with normal peripheral blood monocytes and cultured synovial cells in the presence of recombinant human interleukin-1 (IL-1) in vitro, large numbers of monocytes were seen to be attached to the articular surface. Significant numbers of monocytes invaded the cartilage tissue when the rheumatoid cartilage samples were pre-incubated with 10 U/ml of IL-1. Considerable numbers of monocytes were also attached to normal cartilage when these were pre-incubated with IL-1. It is of interest that recombinant human gamma interferon (γ-IFN) did not enhance monocyte attachment. However, there was a significantly greater attachment of monocytes to rheumatoid than to normal cartilage. When normal cartilage was exposed to collagenase and then incubated with monocytes or synovial cells in the presence of 10 U/ml of IL-1, large numbers of cells were attached to the natural cartilage surface but not to the cut surface. These phenomena were much more intense when the rheumatoid cartilage was pre-incubated with collagenase. These results indicate that increased levels of IL-1 in the rheumatoid joint may play an important role in joint destruction by stimulation of pannus formation by inducing synovial cell attachment to the articular surface.

2-Chloroadenosine but not adenosine induces apoptosis in rheumatoid fibroblasts independently of cell surface adenosine receptor signalling.

The apoptotic effect of adenosine and its analogues was studied in fibroblast‐like synoviocytes derived from rheumatoid arthritis patients (RA‐FLSs). Evoked cell death was quantitatively examined by assessing DNA fragmentation using an enzyme‐liked immunosorbent assay and by measuring phosphatidylserine exposure through flow cytometric analysis of annexin V binding. Exposing cells for 24 h to 2‐chloroadenosine (2‐CADO), a nonspecific, adenosine deaminase (ADA)‐resistant, adenosine receptor (AdoR) agonist, induced DNA fragmentation, and thus apoptosis, in RA‐FLSs at concentrations 50 μM. By contrast, incubation with adenosine for up to 72 h did not evoke DNA fragmentation, even in the presence of ADA inhibitor coformycin and nucleoside transporter inhibitor nitrobenzylmercaptopurin (NBMPR). Transcription of all four AdoR isoforms was detected in RA‐FLSs; nevertheless selective AdoR agonists similarly failed to induce DNA fragmentation. DNA fragmentation evoked by 2‐CADO was inhibited by NBMPR and by 5′‐iodotubercidin, an adenosine kinase inhibitor, but not by xanthine amine congener, an A1 and A2 receptor antagonist, or by selective AdoR antagonists. The nonspecific caspase inhibitor benzyloxycarbonyl‐Val‐Ala‐Asp fluoromethyl ketone abolished the apoptotic effect of 2‐CADO. These results suggest that 2‐CADO induces apoptosis in RA‐FLSs independently of AdoR‐mediated signalling. Instead, 2‐CADO, but not adenosine, is taken up into RA‐FLSs via human equilibrative nucleoside transporter‐1, where it is phosphorylated by adenosine kinase. The resultant phospho‐2‐CADO induces DNA fragmentation by activating a caspase pathway.

Damage of cultured chondrocytes by hydrogen peroxide derived from polymorphonuclear leukocytes: a possible mechanism of cartilage degradation

SummaryTo study the mechanisms of chondrocyte damage, chondrocyte cytotoxicity as shown by chromium-51 release induced by polymorphonuclear leukocytes (PMNLs) was examined. PMNLs significantly enhanced chondrocyte cytotoxicity in the presence of phorbol dibutyrate. This chondrocyte damage was abolished by the addition of catalase, whereas superoxide dismutase and scavengers of hydroxyl radicals and protease inhibitors failed to reverse it. When cartilage matrix components such as hyaluronic acid and various proteoglycans were added to the PMNL-chondrocyte cultures, these components failed to affect the chronium-51 release. These results suggest that the increase in chondrocyte cytotoxicity is due to hydrogen peroxide generated by the PMNLs, and that cartilage matrix components do not prevent it. Hydrogen peroxide from PMNLs may therefore play an important role in cartilage degradation through direct damage of chondrocytes during inflammatory process.

Inhibition of neovascularization in vivo by gold compounds

As mononuclear cell infiltration and growth of pannus critically depend on synovial neovascularization in rheumatoid arthritis (RA), inhibition of the synovial blood vessels would have the potential to reduce rheumatoid inflammation. In this investigation, we studied the effect of gold sodium thiomalate (GST) and auranofin (AUR) on neovascularization in vivo by using a micropocket technique. Both GST and AUR suppressed rabbit corneal neovascularization in a dose-dependent fashion. Significant inhibition was observed by 3 mg/kg GST and 1 mg/kg AUR injected intravenously every other day. These injections maintained serum gold concentrations at the level of 2–5 μg/ml and less than 2 μg/ml in GST-and AUR-injected rabbits, respectively. These are concentrations attained in the serum or synovium of rheumatoid patients treated by gold compounds. Similar inhibition was observed by both intramuscular administration of GST and oral administration of AUR. In contrast, no inhibition was observed when non-steroidal anti-inflammatory drugs (NSAIDs; 20 mg/kg acetylsalicylic acid, 10 mg/kg ibuprofen and 10 mg/kg indomethacin) were injected intravenously on a daily basis. These results suggested that gold compounds have an antiangiogenic effect in vivo. The inhibition of neovascularization by gold compounds suggested that they may suppress rheumatoid synovitis by reducing the number of small blood vessels required for mononuclear cell infiltration and synovial tissue proliferation.

Solitary paralysis of the triceps muscle due to trauma.

We report a rare solitary paralysis of the triceps muscle. The patient, an 18-year-old man who had had a work-related accident, sustained a severe contusion of the proximal posterolateral arm after being struck by a piece of lumber. This injury produced an extraordinary amount of soft-tissue swelling in the region of the trauma. After the accident it was noted that active flexion of the elbow was preserved, but active extension was absent. Three months after injury, surgical exploration of the radial nerve and its rami musculares to the three heads of the triceps muscle was undertaken. Dense adhesions were found fixing the rami musculares to the surfaces of the triceps muscle. Neurolysis of the rami musculares was performed, leading to complete recovery of the triceps muscle. The etiology of this isolated paralysis of the triceps muscle was determined to be dense adhesions compressing and compromising the function of the rami musculares to the three heads of the triceps muscle. These adhesions formed because of severe posttraumatic bleeding into the potential posterior humeral space, where the rami musculares are found.