E-64

E-64 is a potent and irreversible inhibitor of cysteine proteases with an IC₅₀ of 9nM for papain^[1]. E-64 can inhibit the cysteine proteases cathepsin B, H, L and papain, but has no effect on serine proteases or metalloproteinases^[2]. E-64 has antiparasitic activity in vitro and can induce oxidative stress and apoptosis in filarial parasites^[3]. E-64 can improve the preimplantation development of bovine somatic cell nuclear transfer embryos^[4].

In vitro, E-64 (0-50μM) treatment of breast cancer MDA-MB-231 cells for 24h increased the amount of intracellular active cathepsin S and reduced the amount of cathepsin L in a dose-dependent manner^[5]. E-64 (4mM) treatment of porcine alveolar macrophages (PAM) for 48h upregulated the mRNA levels of IFNγ, IL-12 and IFN-α in cells without cytotoxicity^[6].

In vivo, daily intravenous infusion of E-64 (1mg) in Dahl salt-sensitive rats significantly increased the mature forms of the lysosomal proteases Cath B and Cath L in the renal cortex of rats, but had no effect on high-salt diet-induced hypertension and renal damage^[7].

References:
[1] Matsumoto K, Mizoue K, Kitamura K, et al. Structural basis of inhibition of cysteine proteases by E‐64 and its derivatives[J]. Peptide Science, 1999, 51(1): 99-107.
[2] Barrett A J, Kembhavi A A, Brown M A, et al. L-trans-Epoxysuccinyl-leucylamido (4-guanidino) butane (E-64) and its analogues as inhibitors of cysteine proteinases including cathepsins B, H and L[J]. Biochemical Journal, 1982, 201(1): 189-198.
[3] Wadhawan M, Singh N, Rathaur S. Inhibition of cathepsin B by E-64 induces oxidative stress and apoptosis in filarial parasite[J]. PLoS One, 2014, 9(3): e93161.
[4] Min S H, Song B S, Yeon J Y, et al. A cathepsin B inhibitor, E-64, improves the preimplantation development of bovine somatic cell nuclear transfer embryos[J]. Journal of Reproduction and Development, 2014, 60(1): 21-27.
[5] Wilder C L, Walton C, Watson V, et al. Differential cathepsin responses to inhibitor-induced feedback: E-64 and cystatin C elevate active cathepsin S and suppress active cathepsin L in breast cancer cells[J]. The international journal of biochemistry & cell biology, 2016, 79: 199-208.
[6] Liu B, Cui Y, Lu G, et al. Small molecule inhibitor E-64 exhibiting the activity against African swine fever virus pS273R[J]. Bioorganic & Medicinal Chemistry, 2021, 35: 116055.
[7] Blass G, Levchenko V, Ilatovskaya D V, et al. Chronic cathepsin inhibition by E‐64 in Dahl salt‐sensitive rats[J]. Physiological reports, 2016, 4(17): e12950.

E-64是一种有效的不可逆的半胱氨酸蛋白酶抑制剂，对木瓜蛋白酶的IC₅₀为9nM^[1]。E-64能够抑制半胱氨酸蛋白酶组织蛋白酶B、H、L和木瓜蛋白酶，但是对丝氨酸蛋白酶或金属蛋白酶没有作用^[2]。E-64具有体外抗寄生虫活性，可以诱导丝虫寄生虫氧化应激和细胞凋亡^[3]。E-64能够改善牛体细胞核移植胚胎的植入前发育^[4]。

在体外，E-64（0-50μM）处理乳腺癌MDA-MB-231细胞24h，以剂量依赖性方式升高了细胞内活性组织蛋白酶S的量，减少了组织蛋白酶L的量^[5]。E-64（4mM）处理猪肺泡巨噬细胞（PAM）48h，上调了细胞中IFNγ、IL-12和IFN-α的mRNA水平，且没有细胞毒性^[6]。

在体内，E-64（1mg）通过每天静脉导管输注治疗Dahl盐敏感大鼠，显著增加了大鼠体内肾皮质成熟形式的溶酶体蛋白酶Cath B和Cath L，但是对高盐饮食诱导的高血压和肾损害没有效果^[7]。