Stimulatory role of lysophosphatidic acid in cyclooxygenase-2 induction by synovial fluid of patients with rheumatoid arthritis in fibroblast-like synovial cells

While inflammatory cytokines are well-recognized critical factors for the induction of cyclooxygenase-2 (COX-2) in activated fibroblast-like synovial cells, the roles of biologically active components other than inflammatory cytokines in synovial fluid remain unknown. Herein, we assessed the role of lysophosphatidic acid (LPA), a pleiotropic lipid mediator, in COX-2 induction using synovial fluid of patients with rheumatoid arthritis (RA) in fibroblast-like RA synovial cells. Synovial fluid from RA patients stimulated COX-2 induction, which was associated with prostaglandin E(2) production, in RA synovial cells. The synovial fluid-induced actions were inhibited by G(i/o) protein inhibitor pertussis toxin and LPA receptor antagonist 3-(4-[4-([1-(2-chlorophenyl)ethoxy]carbonyl amino)-3-methyl-5-isoxazolyl] benzylsulfanyl) propanoic acid (Ki16425). In fact, LPA alone significantly induced COX-2 expression and enhanced IL-1alpha- or IL-1beta-induced enzyme expression in a manner sensitive to pertussis toxin and Ki16425. RA synovial cells abundantly expressed LPA(1) receptor compared with other LPA receptor subtypes. Moreover, synovial fluid contains a significant amount of LPA, an LPA-synthesizing enzyme autotaxin, and its substrate lysophosphatidylcholine. In conclusion, LPA existing in synovial fluid plays a critical role in COX-2 induction in collaboration with inflammatory cytokines in RA synovial cells. Ki16425-sensitive LPA receptors may be therapeutic targets for RA.     

Possibility of sandwiched liver surgery with molecular targeting drugs, cetuximab and bevacizumab on colon cancer liver metastases: a case report

ABSTRACT: A 31-year-old man with sigmoid colon cancer with concomitant simultaneous multiple liver metastases had received FOLFIRI (leucovorin, fluorouracil and irinotecan) and FOLFOX6 (leucovorin, fluorouracil and oxaliplatin) after an ordinary sigmoidectomy. However, his serum carcinoembryonic antigen (CEA) level increased rapidly during the fifteen months after the operation while he was on FOLFOX6. Abdominal computed tomography revealed expanding multiple liver tumors. As the third line chemotherapy, a combination therapy of cetuximab with irinotecan was given, which markedly reduced his levels of serum CEA, and the size and number of liver tumors. He underwent lateral segmentectomy of the liver and microwave coagulation of the liver metastases in the remnant liver. Thereafter, a good quality of life with tumor dormancy was obtained for 6 months. However, his serum CEA started to rise again in the absence of liver tumors. Therefore, FOLFOX 6 with bevacizumab was chosen as the fourth line chemotherapy, and the serum CEA was reduced with tumor dormancy. A good quality of life was obtained again at 3 years after the first surgery. This report indicates the effectiveness of sandwiched liver surgery with the molecular targeting drugs cetuximab and bevacizumab on multiple liver metastases of colon cancer, and suggests the possibility of a regimen consisting of bevacizumab following cetuximab.     

Treatment with cyclophosphamide reverses acquired resistance to collagen arthritis subsequent to recovery from passive arthritis

Passive arthritis induced by anticollagen antibody was a mild, transient disease from which the animals normally recovered and the rats that had recovered from passive arthritis were resistant to develop a second phase of arthritis following a second administration of anticollagen antibody or the subsequent challenge with type II collagen. However, treatment of the recovered rats with cyclophosphamide (CY) shortly before a second administration of a serum concentrate induced a second episode of acute polyarthritis in 82% of the rats. In addition, CY treatment without further administration of a serum concentrate induced a recurrence of arthritis in 25% of the recovered rats. Similarly, treatment of the recovered rats with CY shortly before the challenge with type II collagen induced a second episode of arthritis in 83% of the rats. However, treatment with CY shortly before the challenge was unable to restore the suppressed humoral response to type II collagen. These results provide evidence that the resistant state is mediated, at least in part, by CY-sensitive events.     

Functions of a rho-specific guanine nucleotide exchange factor in neurite retraction. Possible role of a proline-rich motif of KIAA0380 in localization

The Rho/Rho kinase signaling pathway plays an essential role in neurite retraction and cell rounding in response to G(12/13)-coupled receptor activation in neuronal cells. The Rho guanine nucleotide exchange factor involved in these processes has not been identified. To monitor the activation state of Rho kinase, we developed a vimentin head/Rho kinase chimera, which is intramolecularly phosphorylated in a Rho-dependent manner at Ser(71) of the fused vimentin head. Using this system, we identified a clone termed KIAA0380, which contains the G alpha(12/13)-binding domain as well as a tandem of the Dbl homology/pleckstrin homology (DH/PH) domain, as an activator of Rho/Rho kinase signaling. Molecular dissection analyses revealed that a proline-rich motif C-terminally adjacent to DH/PH domain is essential for plasma membrane localization of KIAA0380 and cortical actin reorganization followed by cell rounding. In contrast, the DH/PH domain of KIAA0380 is localized in the cytoplasm, where it activates Rho/Rho kinase and induces stress fiber formation, consistent with results using p115 Rho guanine nucleotide exchange factor, which has a similar structure to KIAA0380 but lacks a proline-rich motif. These results suggest that upon stimulation, KIAA0380 translocates to the plasma membrane via the proline-rich motif and there activates Rho/Rho kinase signaling. In neuroblastoma Neuro2a cells, KIAA0380 was observed in the tips of neurites, a location where cortical actin reorganization is induced upon stimulation with lysophosphatidic acid. Ectopic expression of the N-terminal fragment inhibited lysophosphatidic acid-induced neurite retraction of Neuro2a cells. These results suggest that KIAA0380 plays an important role in neurite retraction through Rho-dependent signaling.     

Effects of metal ions on the hydrolysis of p-nitrophenyl caproate by modified poly(ethylenimine)s

Hydrolysis of nitrophenyl caproate by modified poly(ethylenimine)s containing imidazole moieties is markedly enhanced in the presence of divalent metal ions. The order of effectiveness is Cu(II) > Co(II) > Zn(II) > Ni(II) > Mn(II), with Cu increasing the rate about 20-fold. The acceleration by the metal ion is much greater in the presence of CH₃COO^? or Cl^? as counterions than in the presence of ClO₄^?. Turnover experiments, in which moles of substrate cleaved were in substantial excess of moles of metal present, established the catalytic nature of the effects of the metals. The extent of binding of Cu(II) by the polymers was measured. Maximum accentuation in rate of hydrolysis of nitrophenyl ester was observed for the imidazole-containing polymer when the ratio of imidazole:Cu(II) was 2.75. Some possible mechanisms for the rate enhancement by metal ions are described.