Production of Anti-platelet Factor 4/Heparin Complex Antibodies After Cardiovascular Surgery.

To study the production of anti-platelet factor 4 (anti-PF4)/heparin complex antibodies of Ig (immunoglobulin) G/IgA/IgM using enzyme-linked immunosorbent assay (ELISA; heparin-induced thrombocytopenia [HIT] antibodies) in 79 patients undergoing cardiovascular surgery, we employed Δoptical density (OD) as a marker of HIT-antibody production. The ΔODs were calculated from the differences in the ODs using ELISA. Patient were classified into 3 ΔOD ranges: ΔOD ≥ 1.0, ΔOD ≥ 0.4 to <1.0, and ΔOD < 0.4. The underlying disease, time course of the postoperative platelet count, D-dimer level, postoperative brain magnetic resonance imaging (MRI), use of cardiopulmonary bypass and postoperative thrombocytosis were not considered for the 3 ΔOD classifications. None of the 6 patients with ΔOD ≥ 1 .0 and a positive functional assay was diagnosed with HIT due to the absence of HIT-derived thrombocytopenia. In conclusion, HIT-antibody production increased until day 7 after heparin cessation and reached a trace level on day 14. It was demonstrated that HIT-antibody production is in remission unless there is any evidence of a further increase during the second week postsurgery.

Synthetic substrates specific to activated plasmin can monitor the enzymatic functional status in situ in breast cancer cells.

We here strove to overcome the limitations of expression analyses such as PCR and IHC, based on molecular recognition between target and probe molecules, by designing synthetic substrates specific to the target molecules to directly estimate the enzymatic functionality in situ. The specific substrate contains a probing unit, which is an organic fragment for specific enzyme binding, and a reactive unit, which is a natural peptide subject to catalysis. In this study, the activation of plasminogen to plasmin was examined in MDA-MB231 breast cancer cells using the plasmin-specific synthetic substrates designed from their inhibitors. The localization and function of the activated plasmin were successfully visualized by fluorophore combined with the specific substrate concurrently. This would be the first time for activated plasmin at work in situ by direct observation. Our concept to directly monitor the functionality of target enzymes can be used straightforwardly for other proteases such as cathepsins or caspases. Also, this substrate concept as a 'tailor-made substrate' would be utilized as a novel functional molecular probe in vivo with appropriate detectable probes.

Synthesis and evaluation of tripeptidic plasmin inhibitors with nitrile as warhead.

Plasmin is best known as the key molecule in the fibrinolytic system, which is critical for clot lysis and can initiate matrix metalloproteinase (MMP) activation cascade. Along with MMP, plasmin is suggested to be involved in physiological processes that are linked to the risk of carcinoma formation. Plasmin inhibitors could be perceived as a promising new principle in the treatment of diseases triggered by plasmin. On the basis of the peptidic sequence derived from the synthetic plasmin substrate, a series of peptidic plasmin inhibitors possessing nitrile as warhead were prepared and evaluated for their inhibitory activities against plasmin and other serine proteases, plasma kallikrein and urokinase. The most potent peptidic inhibitors with the nitrile warhead exhibit the potency toward plasmin (IC(50) = 7.7-11 µM) and are characterized by their selectivity profile against plasma kallikrein and urokinase. The results and molecular modeling of the peptidic inhibitor complexed with plasmin reveal that the P2 residue makes favorable contacts with the open binding pocket comprising the S2 and S3 subsites of plasmin.

Heparin-induced thrombocytopenia in two patients undergoing abdominal aortic aneurysm surgery.

We have experienced 2 cases of heparin-induced thrombocytopenia during unfractionated heparin treatment for disseminated intravascular coagulation after surgery for an abdominal aortic aneurysm. In the first case, as a symptom of disseminated intravascular coagulation gradually improved with antithrombin concentrates and heparin treatment, mesenteric artery thrombosis suddenly occurred, associated with a >50% decrease in platelet count on the 11th day. Although the platelet counts were increasing due to heparin cessation, clinical symptom and coagulation abnormalities worsened to multiple organ failure. In the second case, the platelet count decreased to <10 x 10(4)/microL on the 13th day after the start of unfractionated heparin anticoagulation along with continuous hemodiafiltration, which was indicated for postoperative renal failure. The extracorporeal circuit clotted frequently under an adequate dose of unfractionated heparin. Serologically, heparin-platelet factor 4 complex antibodies were repeatedly detected by enzyme-linked immunosorbent assay. Argatroban, a direct thrombin inhibitor, was introduced as an alternative to unfractionated heparin, and the platelet count improved with a decrease in titers of the antibodies. Disseminated intravascular coagulation is a common complication in cases of abdominal aortic aneurysm and is usually treated in association with unfractionated heparin. It is important to recognize the onset of heparin-induced thrombocytopenia that acute declines in the platelet count and appearance of thrombosis with positive for heparin-platelet factor 4 complex antibodies would suddenly occur in clinical course of disseminated intravascular coagulation.

Anti-heparin/PF4 complexes by ELISA in patients with disseminated intravascular coagulation.

Heparin-induced thrombocytopenia (HIT) is known to complicate disseminated intravascular coagulation (DIC), but rarely to be complicated by DIC. We measured the titers of anti-PF4/hepatin complex antibodies by ELISA (HIT-Elisa) and examined 4 parameters of coagulation and fibrinolysis [D-dimer, thrombin/antithrombin complex (TAT), plasmin/alpha2-plasmin inhibitor complex (PIC), and antithrombin levels] in 80 patients with DIC diagnosed by a DIC scoring system. Fourteen patients were HIT-Elisa-positive, 11 of whom received heparin. In 3 of these 11 patients, platelet counts were < or =10 x 10(9)/l and/or reduced by more than 50% for 5-10 days after the heparin (2 patients treated with renal replacement therapy for chronic uremia and postoperative renal failure, and 1 with DIC from a solid tumor). The 3 patients had an optical density reading of >1.0 and a high level of IgG for HIT antibodies, and were thus considered to have DIC complicated with HIT (DIC-HIT). The other 8 patients had optical density readings of 0.4-1.0, and it was unclear whether their thrombocytopenia was caused by HIT alone or by sustained DIC. There were no significant differences in platelet counts and the 4 parameters of coagulation and fibrinolysis between the patients with DIC-HIT and DIC patients with a weakly positive result (0.4-1.0). No differences were observed in platelet counts, or levels of D-dimer and antithrombin between HIT-Elisa-positive and -negative DIC patients. However, the HIT-Elisa-negative patients showed significantly higher levels of TAT and PIC, presumably reflecting DIC-related hypercoagulability. In conclusion, DIC patients treated with heparin occasionally showed HIT antibody seroconversion and developed HIT. HIT-Elisa could assist in the diagnosis of HIT.

A novel plasmin-inhibitor inhibits the growth of human tumor xenografts and decreases metastasis number.

The novel plasmin inhibitor YO-2, which also exerts an apoptosis-inducing effect on various human tumor cell cultures, was examined regarding its tumor growth inhibitory and antimetastatic action. The tumor growth inhibitory effect of YO-2 was studied using HT-29 human colon carcinoma, HT-18 human melanoma and HT-58 human B cell lymphoma inoculated as xenografts into immuno-deprived mice. Antimetastatic activity was tested on the B16 mouse melanoma muscle-lung model. YO-2 inhibited the growth of all xenografts in the range of 40-50%, when administered s.c. at a dose of 2.0 mg/kg (HT-29, HT-58) or orally at a dose of 0.4 mg/kg (HT-18). YO-2 decreased the number of lung metastasis found in mice inoculated i.m. with B16 melanoma, 4 mg/kg being the most effective. Since YO-2 is the only plasmin inhibitor having antihemorrhagic and also antitumor effect, this compound could be rationally used in combination therapy of neoplastic disease, especially when hemorrhage aggravates the course of the disease.