Macrolide antibiotic; vacuolar H+-ATPase (V-ATPase) (IC50 = 4-400 nmol/mg0

Bafilomycin A1 is exposed to various membrane ATPases, exhibiting an I50 of 400 nmol/mg, 4 nmol/mg, and 50 nmol/mg for the vacuolar ATPases of a plant (Z. mays), an animal (bovine abrenal medulla), and a fungus (N. crassa). The 50% inhibition of ATPase activity expressed as μmol of Bafilomycin A1 per mg of protein is known as the I50 values[1]. By blocking both V-ATPase-dependent acidification and Ca-P60A/SERCA-dependent autophagosome-lysosome fusion, bafilomycin A1 ((-)-Bafilomycin A1) impairs autophagic flux[2]. Pediatric B-cell acute lymphoblastic leukemia cells are specifically and efficiently inhibited and killed by bafilomycin A1 at a low concentration (1 nM). It induces apoptosis without the need for caspase and targets mitochondria, the autophagy pathway, and both early and late stages of the pathway. Beclin 1 binds to Bcl-2 when bafilomycin A1 is present, further inhibiting autophagy and encouraging apoptotic cell death[5]. Bafilomycin A1 inhibits the growth of the HO-8910 ovarian cancer and BEL-7402 hepatocellular carcinoma cell lines as well as their ability to spread. Bafilomycin A1 is thought to cause apoptosis, according to tests using capsase-3 and -9 and transmission electron microscopy[6]. Whether or not they are transformed, NIH-3T3 fibroblasts, PC12 and HeLa cells, and golden hamster embryos are among the many cultured cells whose growth is dose-dependently inhibited by bafilomycin A1. When it comes to inhibiting cell growth, bafilomycin A1's IC50 ranges from 10 to 50 nM[7].

Low-dose Bafilomycin A1 (0.1 mg/kg) administered over an extended period of time modestly reduces the tumor volume, but the final tumor volume is not substantially different from the control. After 21 days, however, long-term administration of a high dose of Bafilomycin A1 (1 mg/kg) effectively slows tumor growth as compared to controls[8]. The survival of B-cell acute lymphoblastic leukemia (B-ALL) xenograft mice with advanced disease is prolonged by bafilomycin A1 (0.1 mg/kg or 1 mg/kg; intraperitoneally for 3 days)[9].

Autophagosome-lysosome fusion and autolysosome acidification constitute late steps in the autophagic process necessary to maintain functional autophagic flux and cellular homeostasis. Both of these steps are disrupted by the V-ATPase inhibitor bafilomycin A1, but the mechanisms potentially linking them are unclear. We recently revisited the role of lysosomal acidification in autophagosome-lysosome fusion, using an in vivo approach in Drosophila. By genetically depleting individual subunits of the V-ATPase, we confirmed its role in lysosomal acidification and autophagic cargo degradation. Surprisingly, vesicle fusion remained active in V-ATPase-depleted cells, indicating that autophagosome-lysosome fusion and autolysosome acidification are 2 separable processes. In contrast, bafilomycin A1 inhibited both acidification and fusion, consistent with its effects in mammalian cells. Together, these results imply that this drug inhibits fusion independently of its effect on V-ATPase-mediated acidification. We identified the ER-calcium ATPase Ca-P60A/dSERCA as a novel target of bafilomycin A1. Autophagosome-lysosome fusion was defective in Ca-P60A/dSERCA-depleted cells, and bafilomycin A1 induced a significant increase in cytosolic calcium concentration and disrupted Ca-P60A/SERCA-mediated fusion. Thus, bafilomycin A1 disrupts autophagic flux by independently inhibiting V-ATPase-dependent acidification and Ca-P60A/SERCA-dependent autophagosome-lysosome fusion.[2]

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Bafilomycin A1 is known as a strong inhibitor of the vacuolar type H(+)-ATPase in vitro, whereas other type ATPases, e.g. F1,F0-ATPase, are not affected by this antibiotic (Bowman, E.M., Siebers, A., and Altendorf, K. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 7972-7976). Effects of this inhibitor on lysosomes of living cultured cells were tested. The acidification of lysosomes revealed by the incubation with acridine orange was completely inhibited when BNL CL.2 and A431 cells were treated with 0.1-1 microM bafilomycin A1. The effect was revealed by washing the cells. Both studies using 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine and fluorescein isothiocyanate-dextran showed that the intralysomal pH of A431 cells increased from about 5.1-5.5 to about 6.3 in the presence of 1 microM bafilomycin A1. The pH increased gradually in about 50 min. In the presence of 1 microM bafilomycin A1, 125I-labeled epidermal growth factor (EGF) bound to the cell surface at 4 degrees C was internalized normally into the cells at 37 degrees C but was not degraded at all, in marked contrast to the rapid degradation of 125I-EGF in the control cells without the drug. Immunogold electron microscopy showed that EGF was transported into lysosomes irrespective of the addition of bafilomycin A1. These results suggest that the vacuolar type H(+)-ATPase plays a pivotal role in acidification and protein degradation in the lysosomes in vivo[4].

Bafilomycin A1 was used at a concentration of 1 nM unless indicated with different doses. Leukemia cell lines RS4;11, NB4, HL-60, K562 and BV173 as well as Leukemia cell lines 697 and Nalm-6 were used. The leukemia cells were grown in RPMI 1640 medium with 10% fetal bovine serum at 37°C, in a 5% CO2 incubator. Experimental cultures were initiated by reculturing exponentially growing cells at a density of 0.2×106 cells/mL and sampled at the indicated times for different analyses. The viability of the leukemia cells collected from the medium was determined by counting total and trypan blue cells under a microscope[3].

Animals and the B-cell acute lymphoblastic leukemia xenograft model[3]
Male and female mice were used equally in all experiments and littermates were used as controls. The 697 B-ALL cells were injected at a dose of 5×106 cells/animal into 6- to 8-week-old male NOD-SCID mice or C57BL/6J control mice. Cells were allowed to proliferate in vivo for 6 days and then the transplanted mice were injected intraperitoneally with phosphate-buffered saline or bafilomycin A1 (0.1 mg/kg or 1 mg/kg). Mice were killed on day 30 after starting the treatment. Peripheral blood, bone marrow, livers and spleens were analyzed for the presence of leukemic cells by flow cytometry. Engraftment was detected by flow cytometry using antibodies recognizing E2A/PBX1. Liver and spleen cells were collected for analysis.

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0 ~ 10-5 mol/L; 30 mins

Young freshwater tilapias

[1]. Bafilomycins: a class of inhibitors of membrane ATPases from microorganisms, animal cells, and plant cells. Proc Natl Acad Sci U S A. 1988;85(21):7972-7976.

[2]. Bafilomycin A1 disrupts autophagic flux by inhibiting both V-ATPase-dependent acidification and Ca-P60A/SERCA-dependent autophagosome-lysosome fusion. Autophagy. 2015;11(8):1437-1438.

[3]. Bafilomycin A1 targets both autophagy and apoptosis pathways in pediatric B-cell acute lymphoblastic leukemia. Haematologica. 2015;100(3):345-356.

[4]. Bafilomycin A1, a specific inhibitor of vacuolar-type H(+)-ATPase, inhibits acidification and protein degradation in lysosomes of cultured cells. J Biol Chem. 1991;266(26):17707-17712.

[5]. Bafilomycin A1 targets both autophagy and apoptosis pathways in pediatric B-cell acute lymphoblastic leukemia. Haematologica. 2015 Mar;100(3):345-56.

[6]. Bafilomycin A1 inhibits the growth and metastatic potential of the BEL-7402 liver cancer and HO-8910 ovarian cancer cell lines and induces alterations in their microRNA expression. Exp Ther Med. 2015 Nov;10(5):1829-1834.

[7]. Inhibition of cell growth by bafilomycin A1, a selective inhibitor of vacuolar H(+)-ATPase. In Vitro Cell Dev Biol Anim. 1993 Nov;29A(11):862-6.

[8]. Bafilomycin A1 induces apoptosis in the human pancreatic cancer cell line Capan-1. J Pathol. 1998 Jul;185(3):324-30.

[9]. Bafilomycin A1 and intracellular multiplication of Legionella pneumophila. Antimicrob Agents Chemother. 1997;41(1):212-214.

[10]. Bafilomycin A1 targets both autophagy and apoptosis pathways in pediatric B-cell acute lymphoblastic leukemia. Haematologica. 2015 Mar;100(3):345-56.

Bafilomycin A1 is the most used of the bafilomycins, a family of toxic macrolide antibiotics derived from Streptomyces griseus. It has a role as a toxin, a fungicide, an EC 3.6.3.10 (H(+)/K(+)-exchanging ATPase) inhibitor, an EC 3.6.3.14 (H(+)-transporting two-sector ATPase) inhibitor, a bacterial metabolite, a potassium ionophore, an autophagy inhibitor, an apoptosis inducer and a ferroptosis inhibitor. It is a member of oxanes, a macrolide antibiotic and a cyclic hemiketal.
The bafilomycins refer to a category of toxic macrolide antibiotics that are derivatives of Streptomyces griseus. These compounds all appear in the same fermentation and have similar biological activity. Bafilomycins are specific inhibitors of vacuolar-type H+-ATPase. (V-ATPase). The most commonly utilized bafilomycin is bafilomycin A1. This is a useful tool as it can prevent the re-acidification of synaptic vesicles once they have undergone exocytosis.
(3Z,5E,7R,8S,9S,11E,13E,15S,16R)-16-{(2S,3R,4S)-4-[(2R,4R,5S,6R)-2,4-dihydroxy-6-isopropyl-5-methyltetrahydro-2H-pyran-2-yl]-3-hydroxypentan-2-yl}-8-hydroxy-3,15-dimethoxy-5,7,9,11-tetramethyloxacyclohexadeca-3,5,11,13-tetraen-2-one has been reported in Streptomyces with data available.

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Mechanism of Action
The bafilomycins are a family of toxic macrolide antibiotic derived from Streptomyces griseus. These compounds all appear in the same fermentation and have quite similar biological activity. Bafilomycins are specific inhibitors of vacuolar-type H+-ATPase. (V-ATPase).

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Various membrane ATPases have been tested for their sensitivity to bafilomycin A1, a macrolide antibiotic. F1F0 ATPases from bacteria and mitochondria are not affected by this antibiotic. In contrast, E1E2 ATPases--e.g., the K+-dependent (Kdp) ATPase from Escherichia coli, the Na+,K+-ATPase from ox brain, and the Ca2+-ATPase from sarcoplasmic reticulum--are moderately sensitive to this inhibitor. Finally, membrane ATPases from Neurospora vacuoles, chromaffin granules, and plant vacuoles are extremely sensitive. From this we conclude that bafilomycin A1 is a valuable tool for distinguishing among the three different types of ATPases and represents the first relatively specific potent inhibitor of vacuolar ATPases.[1]

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B-cell acute lymphoblastic leukemia is the most common type of pediatric leukemia. Despite improved remission rates, current treatment regimens for pediatric B-cell acute lymphoblastic leukemia are often associated with adverse effects and central nervous system relapse, necessitating more effective and safer agents. Bafilomycin A1 is an inhibitor of vacuolar H(+)-ATPase that is frequently used at high concentration to block late-phase autophagy. Here, we show that bafilomycin A1 at a low concentration (1 nM) effectively and specifically inhibited and killed pediatric B-cell acute lymphoblastic leukemia cells. It targeted both early and late stages of the autophagy pathway by activating mammalian target of rapamycin signaling and by disassociating the Beclin 1-Vps34 complex, as well as by inhibiting the formation of autolysosomes, all of which attenuated functional autophagy. Bafilomycin A1 also targeted mitochondria and induced caspase-independent apoptosis by inducing the translocation of apoptosis-inducing factor from mitochondria to the nucleus. Moreover, bafilomycin A1 induced the binding of Beclin 1 to Bcl-2, which further inhibited autophagy and promoted apoptotic cell death. In primary cells from pediatric patients with B-cell acute lymphoblastic leukemia and a xenograft model, bafilomycin A1 specifically targeted leukemia cells while sparing normal cells. An in vivo mouse toxicity assay confirmed that bafilomycin A1 is safe. Our data thus suggest that bafilomycin A1 is a promising candidate drug for the treatment of pediatric B-cell acute lymphoblastic leukemia.[3]

C35H58O9

622.83

622.408

C, 67.49; H, 9.39; O, 23.12

88899-55-2

88899-56-3 (Bafilomycin B1)

6436223

White to light yellow solid powder

1.1±0.1 g/cm3

770.1±60.0 °C at 760 mmHg

232.2±26.4 °C

0.0±6.0 mmHg at 25°C

1.535

3.88

4

9

7

44

1060

12

C[C@H]1C/C(=C/C=C/[C@@H]([C@H](OC(=O)/C(=C/C(=C/[C@H]([C@H]1O)C)/C)/OC)[C@@H](C)[C@H]([C@H](C)[C@]2(C[C@H]([C@@H]([C@H](O2)C(C)C)C)O)O)O)OC)/C

XDHNQDDQEHDUTM-JQWOJBOSSA-N

InChI=1S/C35H58O9/c1-19(2)32-24(7)27(36)18-35(40,44-32)26(9)31(38)25(8)33-28(41-10)14-12-13-20(3)15-22(5)30(37)23(6)16-21(4)17-29(42-11)34(39)43-33/h12-14,16-17,19,22-28,30-33,36-38,40H,15,18H2,1-11H3/b14-12+,20-13+,21-16+,29-17-/t22-,23+,24-,25-,26-,27+,28-,30-,31+,32+,33+,35+/m0/s1

(3Z,5E,7R,8S,9S,11E,13E,15S,16R)-16-[(2S,3R,4S)-4-[(2R,4R,5S,6R)-2,4-dihydroxy-5-methyl-6-propan-2-yloxan-2-yl]-3-hydroxypentan-2-yl]-8-hydroxy-3,15-dimethoxy-5,7,9,11-tetramethyl-1-oxacyclohexadeca-3,5,11,13-tetraen-2-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage.  (2). This product is not stable in solution, please use freshly prepared working solution for optimal results.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: 2.5 mg/mL (4.01 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (3.34 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (3.34 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)