Study on the activity of recombinant mutant tissue-type plasminogen activator fused with the C-terminal fragment of hirudin

Molecular dynamic and pharmacological studies on protein-engineered hirudin variants of Hirudinaria manillensis and Hirudo medicinalis

BACKGROUND AND PURPOSE

Hirudin variants are the most powerful thrombin inhibitors discovered to date, with a lower risk of bleeding than heparin. For anticoagulation, the C-termini of hirudins bind to the exocite I of thrombin. Anticoagulant effects of gene-recombinant hirudin are weaker than natural hirudin for the reason of lacking tyrosine-O-sulfation at C terminus.

EXPERIMENTAL APPROACH

The integrative pharmacological study applied molecular dynamic, molecular biological, and in vivo and in vitro experiments to elucidate the anticoagulant effects of protein-engineered hirudins.

KEY RESULTS

Molecular dynamic (MD) analysis showed that modifications of the C-termini of hirudin variant 1 of Hirudo medicinalis (HV1) and hirudin variant 2 of Hirudinaria manillensis (HM2) changed the binding energy of the C-termini to human thrombin. The study indicated Asp61 of HM2 that corresponds to sulfated Tyr63 of HV1 is critical for inhibiting thrombin activities, and the anticoagulant effects of HV1 and HM2 were improved when the amino acid residues adjacent to Asp61 were mutated to Asp, such as the prolongation of the activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) of human blood, and decreased Ki and IC₅₀ values. In the in vivo experiments, mutations at C-termini of HV1 and HM2 significantly changed APTT, PT and TT.

CONCLUSION AND IMPLICATIONS

The study indicated that the anticoagulant effects of gene-engineered HM2 are stronger than gene-engineered HV1, and HM2-E60D-I62D has the strongest effects and could be an antithrombotic medicine with better therapeutic effects.

Anti-Inflammatory Dipeptide, a Metabolite from Ambioba Secretion, Protects Cerebral Ischemia Injury by Blocking Apoptosis Via p-JNK/Bax Pathway

MQ (l-methionyl-l-glutamic acid), anti-inflammatory dipeptide, is one of the metabolites of monocyte locomotion inhibitory factor, a thermostable pentapeptide secreted by Entamoeba histolytica. Monocyte locomotion inhibitory factor injection has been approved as an investigational drug for the potential neural protection in acute ischemic stroke. This study further investigated the neuroprotective effect of MQ in ischemic brain damage. Ischemia-reperfusion injury of the brain was induced in the rat model by middle cerebral artery occlusion. 2,3,5-triphenyltetrazolium chloride staining assay was used to measure cerebral infarction areas in rats. Laser Doppler measurement instrument was used to detect blood flow changes in the rat model. Nissl staining and NeuN staining were utilized to observe the numbers and structures of neuron cells, and the pathological changes in the brain tissues were examined by hematoxylin–eosin staining. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) staining was used to assess cell apoptosis. The changes in oxidative stress indexes, superoxide dismutase and malondialdehyde (MDA), were measured in serum. Methyl thiazolyl tetrazolium was used to measure the survival rates of PC12 cells. Flow cytometry assessed the apoptosis rates and the levels of reactive oxygen species. Real-time PCR was used to evaluate the mRNA expression levels, and Western blotting was used to analyze the changes in protein levels of p-JNK, Bax, cleaved Caspase3. We revealed that MQ improved neurobehavior, decreased cerebral infarction areas, altered blood flow volume, and the morphology of the cortex and hippocampus. On the other hand, it decreased the apoptosis of cortical neurons and the levels of MDA, and increased the levels of superoxide dismutase. In vitro studies demonstrated that MQ enhanced the cell survival rates and decreased the levels of reactive oxygen species. Compared to the oxygen-glucose deprivation/reperfusion group, the protein and mRNA expressions of p-JNK, Bax, cleaved Caspase3 was decreased significantly. These findings suggested that MQ exerts a neuroprotective effect in cerebral ischemia by blocking apoptosis via the p-JNK/Bax pathway.