Complement activation in patients with primary antiphospholipid syndrome

OBJECTIVE

To investigate the significance of complement activation in patients with primary antiphospholipid syndrome (APS).

METHODS

Thirty-six patients with primary APS, 42 control patients with non-systemic lupus erythematosus (SLE) connective tissue diseases, and 36 healthy volunteers were analysed retrospectively. Serum complement levels (C3, C4, CH(50)) and anaphylatoxins (C3a, C4a, C5a) were examined in all subjects, and serum complement regulatory factors (factor H and factor I) were measured in patients with primary APS. Plasma anticoagulant activity was determined in a mixing test using the activated partial thromboplastin time.

RESULTS

Serum complement levels were significantly lower in patients with primary APS than in patients with non-SLE connective tissue diseases (mean (SD) C3: 81.07 (17.86) vs 109.80 (22.76) mg/dl, p<0.001; C4: 13.04 (8.49) vs 21.70 (6.96) mg/dl, p<0.001; CH(50): 31.32 (8.76) vs 41.40 (7.70) U/ml, p<0.001) or healthy volunteers. Only two healthy subjects with low serum C4 levels showed hypocomplementaemia, whereas most patients with primary APS showed raised serum C3a and C4a. No subjects showed raised C5a. Patients with primary APS with low serum C3 or C4 had significantly higher levels of C3a or C4a than healthy controls. No patients had low serum complement regulatory factors. Among patients with primary APS, hypocomplementaemia was significantly more common in those with high anticoagulant activity than in those with low or normal activity.

CONCLUSION

Hypocomplementaemia is common in patients with primary APS, reflecting complement activation and consumption, and was correlated with anticoagulant activity, suggesting that antiphospholipid antibodies may activate monocytes and macrophages via anaphylatoxins produced in complement activation.

Effect of a highly selective plasma-kallikrein synthetic inhibitor on contact activation relating to kinin generation, coagulation and fibrinolysis

A highly selective inhibitor of plasma-kallikrein (PK), N-(trans-4-aminomethylcyclohexylcarbonyl)-L-phenylalanine 4-carboxymethyl-anilide hydrochloride, was designed and synthesized by the authors' group, called PKSI-527 in our laboratories. (I) PKSI-527 inhibited PK with a Ki value of 0.81 microM. By contrast, the Ki values for glandular kallikrein (GK), plasmin, thrombin, urokinase and factor Xa were greater than 500 microM, 390 microM, greater than 500 microM, 200 microM and greater than 500 microM, respectively. (II) Effects of PKSI-527 on bradykinin (BK) generation, coagulation and fibrinolysis by contact activation were examined using human plasma. (a) BK generation induced by kaolin appeared to be reduced by PKSI-527. Furthermore BK generation induced by lambda-carrageenan, a strong inflammatory agent, was also reduced by PKSI-527. (b) Partial thromboplastin time (PTT) was prolonged by PKSI-527, indicating the suppression of the intrinsic coagulation system. (c) Euglobulin clot lysis time (ECLT) of plasma which was shortened by activation with kaolin, was prolonged by the addition of PKSI-527, confirming the participation of PK in contact-fibrinolysis. These results indicate that PKSI-527 shows great potential in elucidating the significance of PK, and as such deserves further investigation.

Up regulated expression of tumour necrosis factor {alpha} converting enzyme in peripheral monocytes of patients with early systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is accompanied by abnormalities in humoral and cellular immune systems.

OBJECTIVE

To determine the genes specifically expressed in the immune system in SSc by analysis of the gene expression profile of peripheral blood mononuclear cells (PBMC) from patients with SSc, including those treated with haematopoietic stem cell transplantation (HSCT). Additionally, to investigate the clinical significance of the up regulation of tumour necrosis factor alpha (TNFalpha) converting enzyme (TACE).

METHODS

PBMC from patients with SSc (n = 23) and other autoimmune diseases (systemic lupus erythematosus (SLE, n = 16), rheumatoid arthritis (RA, n = 29)), and from disease-free controls (n = 36) were examined. Complementary DNA arrays were used to evaluate gene expression of PBMC, in combination with real time quantitative polymerase chain reactions. TACE protein expression in PBMC was examined by fluorescence activated cell sorter (FACS).

RESULTS

In patients with SSc 118 genes were down regulated after HSCT. Subsequent comparative analysis of SSc without HSCT and healthy controls indicated SSc-specific up regulation for three genes: monocyte chemoattractant protein-3 (p = 0.0015), macrophage inflammatory protein 3alpha (p = 0.0339), and TACE (p = 0.0251). In the FACS analysis, TACE protein was mainly expressed on CD14(+) monocytes both in patients with SSc and controls. TACE expression on CD14(+) cells was significantly increased in patients with early SSc (p = 0.0096), but not in those with chronic SSc, SLE, or RA. TACE protein levels in SSc monocytes correlated with the intracellular CD68 levels (p = 0.0016).

CONCLUSIONS

Up regulation of TACE expression was a unique profile in early SSc, and may affect the function of TNFalpha and other immunoregulatory molecules.

Synthesis of tripeptide chloromethyl ketones and examination of their inhibitory effects on plasmin and plasma kallikrein

With the aim of obtaining selective synthetic inhibitors of plasmin and plasma kallikrein, D-Ile-Phe-Lys-CH2Cl, Ile-Phe-Lys-CH2Cl, D-Ile-Phe-Arg-CH2Cl and Ile-Phe-Arg-CH2Cl were synthesized and their inhibitory activity against plasmin, plasma kallikrein and other trypsin-like serine proteinases was examined. Among them, D-Ile-Phe-Arg-CH2Cl exhibited a highly selective inhibitory activity against plasma kallikrein, yet D-Ile-Phe-Lys-CH2Cl exhibited nearly the same order of inhibitory activity against plasmin as well as plasma kallikrein.

Use of an active center-directed plasmin inhibitor elucidates the multiplicity of plasmin actions

In our studies, designed to synthesize an active center-directed plasmin (PL) inhibitor, N-(4-aminomethylbenzoyl)-4-(3-picolyloxy)-L-phenylalanine n-hexylamide dihydrochloride (PASI-535) was found. We characterized PASI-535 and analyzed the actions of PL, comparing with those of PASI-535 and tranexamic acid (t-AMCHA). (1) PASI-535 strongly inhibited not only fibrinolysis (IC50: 2.9 x 10(-6) M) but also amidolysis (Ki value: 2.9 x 10(-6) M) and fibrinogenolysis (IC50: 4.5 x 10(-6) M) induced by PL. While t-AMCHA which strongly inhibited fibrinolysis (IC50: 6.0 x 10(-5) M), rarely inhibited amidolysis (Ki value: 4.0 x 10(-2) M) and fibrinogenolysis (IC50: 1.0 x 10(-2) M). (2) PL is able to liberate kinins by degrading kininogen. This kinin-generation by PL was inhibited by 2 x 10(-5) M PASI-535. However, it was little inhibited even by 1 x 10(-3) M t-AMCHA. (3) The inhibitory effect of PASI-535 and t-AMCHA on tumor growth was studied. In sarcoma-180 bearing mice, ascites retention and the increase of tumor cells were markedly suppressed by subcutaneous injection of PASI-535, either 30 mg/kg/day or 50 mg/kg/day, for 5 days, and the inhibitory effect was dose-dependent. Although t-AMCHA also reduced both ascites retention and the increase of tumor cells, it needed approximately 40 times (2 g/kg/day) the amount of PASI-535 to exert these effects. PASI-535 may be a useful tool in analyzing the multiplicity of PL actions. Moreover, PASI-535 can be used as an antifibrinolytic drug which has a mechanism of function different from that of t-AMCHA.

Highly selective synthetic inhibitors with regard to plasma-kallikrein activities

The synthetic inhibitors of plasma kallikrein (PK) were found, which are called PKSI-1007, PKSI-0180 and PKSI-0527 in our laboratories. (1) The inhibitors inhibited PK competitively with D-Pro-Phe-Arg-pNA and the Ki values obtained were considerably small, 10(-6) M-10(-7) M. However, the Ki values for glandular kallikrein (GK), plasmin (PL), thrombin (TH) and factor Xa (FXa) were larger. In particular, a selectivity of PKSI-0527 towards PK was very high and the toxicity was weak (i.v. LD50 for mice is over 100 mg/kg). (2) The inhibitors were effective (a) to prevent the bradykinin formation in the kaolin-activated human plasma and the acid-treated ascites taken from the mice bearing Sarcoma 180, (b) to prolong the coagulation time by contact activation, and (c) to inhibit the enhancement of ADP-platelet aggregation by PK. The results indicated that the some PKSI-inhibitors will be much useful for the basic studies, furthermore they deem to be even promising towards the clinical application.