Although natural hirudin is in great demand in clinical and pharmaceutical research, it is not easy to obtain. With the gradual exhaustion of natural leech resources, the gap between supply and demand is expanding year by year. In order to alleviate the shortage of leech resources, researchers obtained the gene sequence of natural hirudin by chemical synthesis, reverse transcription and other methods, and transferred the gene sequence to Escherichia coli, fermentation in Pichia pastoris, Bacillus subtilis and other fungi, and further separation and purification to obtain recombinant hirudin. Currently, there are many variants of recombinant hirudin, mainly 3 types: HV1, HV2, HV3. Structurally, the recombinant hirudin differs from the natural hirudin only in the 63-position tyrosine. The 63-position tyrosine of natural hirudin is sulfonated to Tyr-SO3, while the recombinant hirudin is not sulfonated. The main secondary structure of hirudin is almost identical to that of natural hirudin; functionally, the recombinant hirudin has an inherent structural defect that makes its anticoagulant activity lower than that of natural hirudin. Pharmacological Action Anticoagulant and Antithrombotic Effect The study found that recombinant hirudin has obvious antithrombotic effect, and both injection and oral administration can exert the drug effect. In animal experiments, for venous thrombosis and arterial thrombosis in rats and disseminated intravascular coagulation in rabbits, recombinant hirudin can significantly prolong the activated partial thromboplastin time, and inhibit the level of fibrinogen and antithrombin activity, so as to achieve anti-inflammatory effects, anti-coagulation and anti-antithrombotic effects. Its anti-venous thrombosis intensity is about 4 times that of heparin, and the dose of recombinant hirudin is negatively correlated with the dry weight of thrombus. Its mechanism of action may be related to affecting the extrinsic coagulation system and promoting fibrinolysis: 1) Recombinant hirudin can prolong plasma prothrombin time (PT) and increase the release of tissue plasminogen activator (t-PA) , while inhibiting the release of PAI-1, and has endothelial protection; 2) Recombinant hirudin can effectively inhibit thrombin, especially interfere with or hinder the formation of thrombin-thrombomodulin complex (Th-TM). Inhibit the activation of TAFI by Th or Th-TM, reduce the production of TAFIa, and then achieve the purpose of antithrombotic. Anti-Atherosclerotic Effect Recombinant hirudin can improve apolipoprotein E knockout (ApoE-/-) mice atherosclerosis, regulate serum lipid levels, inhibit vascular endothelial proliferation, and reduce collagen fiber proliferation, thereby improving ApoE-/- mice Studies have found that recombinant hirudin can also reduce the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), and promote the expression of CD36 and Toll-like receptor 4 (TLR4) /NF-κB, thereby improving the chronic inflammatory response of aortic atherosclerosis. Recombinant hirudin may also delay the occurrence and development of atherosclerosis by down-regulating the expression of matrix sympathetic molecule 1, Orai1 protein, and transient receptor potential channel 1. Antitumor Effect The study found that recombinant hirudin can significantly inhibit the proliferation of human hepatoma SMMC-7721 cells and promote their apoptosis, and can effectively reverse the growth promotion and apoptosis resistance caused by thrombin. The molecular mechanism may be that recombinant hirudin significantly reduces the apoptosis. The anti-apoptotic gene Bcl-2 mRNA and protein expression in tumor cells was increased, and the pro-apoptotic gene Bax mRNA and protein expression was increased. In addition, some studies have found that recombinant hirudin can reduce the expression of protease-activated receptor (PAR-1) in laryngeal cancer cells, thereby inhibiting the expression of VEGF and matrix metalloproteinase-2 (MMP-2), thereby inhibiting the expression of laryngeal cancer cells and metastases, and ultimately exert an anti-tumor effect. Reduce Brain Damage Studies have found that recombinant hirudin can significantly reduce cerebral edema in rats with cerebral hemorrhage by specifically inhibiting thrombin and intervening in the inflammatory response of surrounding tissue of cerebral edema, and can improve the neurological deficit of rats for a long time, and significantly reduce the residual rate of cerebral hemorrhage caused by cerebral hemorrhage. Recombinant hirudin may reduce brain injury by intervening in the inflammatory tissue surrounding hematoma in rat cerebral hemorrhage by reducing the expression of TNF-α and ICAM-1. Improves the Survival Rate of Random Skin Flaps In the rabbit ear vein congestion model, the local application of recombinant hirudin can induce the expression of bFGF and promote the proliferation of microvessels, thereby improving the flap congestion state and improving the survival rate of the flap with venous congestion. The study found that recombinant hirudin can reduce the local malondialdehyde (MDA) level in the random flap congestion model rat, reduce the local inflammatory response of the flap, reduce the local endothelin level of the congestion flap, and improve the survival rate of the random flap. Another study found that for skin avulsion injury in rats, local application of recombinant hirudin can effectively reduce the effect of adhesion factor CD11b/CD18 in blood and ICAM-1 in tissue, reduce tissue inflammatory response, and improve the effect of vascular endothelial cell injury in ischemia-reperfusion process, thereby significantly improving the healing rate of skin flaps after skin avulsion injury. Relieve Renal Interstitial Fibrosis The researchers used unilateral tubal ligation to prepare a mouse model of renal fibrosis. After treatment with recombinant hirudin, the researchers found that the renal function of the mice was improved, the renal cortex was thinned, the degree of renal lesions was reduced, and the positive staining area of collagen fibers in the renal interstitium was found. The expression levels of α-smooth muscle actin (α-SMA) and fucosyltransferase-8 (FUT-8) in renal tissue were significantly reduced, indicating that recombinant hirudin could alleviate renal interstitial fibrosis. Anti-Cataract Effect Scientists used D-galactose and sodium selenite to induce cataract models in lactating rats respectively, used recombinant hirudin for intervention treatment, and used rabbits to conduct eye irritation experiments to test the safety of recombinant hirudin. The results showed that recombinant hirudin could reduce the turbidity and MDA level of the rat lens, and increase the level of superoxide dismutase (SOD), and had good preventive and therapeutic effects on both sugar-induced cataracts and selenium-induced cataracts, and it was safe and non-irritating. Another study found that in the human lens epithelial cell cataract model induced by high concentration of galactose, recombinant hirudin can reduce the expression of heat shock protein 70 (Hsp70), Hsp27 and αB crystal protein, and significantly alleviate the tolerance of Hsp induced by high concentration of galactose. That is, reducing the damage of high concentrations of galactose to lens epithelial cells, thereby protecting lens epithelial cells. Other Functions The study found that recombinant hirudin can alleviate experimental autoimmune encephalomyelitis (EAE) in mice, and the mechanism of action may be related to the inhibition of MMP-9 and inducible nitric oxide synthase (iNOS) mRNA expression in mouse brain tissue, thereby reducing MMP-9 and NO levels. Cigarette smoking combined with intratracheal injection of lipopolysaccharide (LPS) to establish a rat model of chronic obstructive pulmonary disease (COPD). Recombinant hirudin can reduce airway remodeling in COPD rats after intervention. TNF-α levels in bronchopulmonary tissue, reduced phosphorylation of extracellular protein-regulated kinase (p-EPK) expression.