Book of abstract 2008

Protease inhibitory and cytotoxic effects of “non-toxic” cyclic peptides
from cyanobacteria
Anja Bubik1, Bojan Sedmak1, Marko Novinec2, Brigita Lenarčič2 ,3, Tamara Lah Turnšek1
1Dept. of Genetic Toxicology and Cancer Biology, National Institute of Biology, Večna pot 111, POB 141,
1001 Ljubljana, Slovenia; 2Dept. of Biochemistry and Molecular Biology, Jožef Stefan Institute, Jamova
39, 1000 Ljubljana, Slovenia; 3Faculty of Chemistry and Chemical Technology, University of Ljubljana,
Aškerčeva 5, 1000 Ljubljana, Slovenia
Toxic cyanobacterial blooms are common events also in the republic of Slovenia (1).
These organisms are a rich source of various metabolites with strong biological activities
(2, 3). Various “non-toxic” cyclic peptides belonging to two main groups, depsipeptides
and cyclic peptides with the ureido linkage inhibit serine proteases that play an important
role also in the human organism (4). We have tested three representatives isolated from
the Planktothrix rubescens bloom (2); one depsipeptide planktopeptin BL1125 (PP
BL) and two ureido linkage possessing representatives, anabaenopeptin B (AnP B) and
anabaenopeptin F (AnP F). Our aims were (a) to find, which physiological important
serine proteases are inhibited by PP BL, AnP B and AnP F, and (b) to investigate the
possible influence of PP BL, AnP B and AnP F on the growth characteristic of one normal
cell line (human astrocytes NHA) and two tumour cell lines, human glioblastoma cells
(U87) and human large cell carcinoma (LCLC 103H).
Our results have proved a strong inhibition of leukocyte (K
p6
i
= 15.8 nM) and pancreatic
(K i
= 5.8 nM) elastase and chymotrypsin (K i
= 2.3 nM) with PP BL and a weaker
inhibition of these enzymes with AnP B and AnP F. Planktopeptin has been also effective
in inhibiting the elastinolytic activity of leukocyte elastase even when the enzyme has been
allowed to form a tightly bound complex with elastin. The examined cyclic peptides have
demonstrated no inhibitory activity towards trypsin, urokinase, kallikrein 1 and cysteine
chatepsins B, K, L and S. The cytotoxic effects of PP BL, AnP B and AnP F on all tested
cell lines were not observed within 24 hours in concentration range 0.1-10 μM. They have
had a significant influence on the metabolic activity of normal NHA cells after 48, 72 and
96 hour exposures, but not on any of tumour cell lines.
The selective inhibitory activity of cyclic peptides on elastase is important for a potential
application in inflammatory diseases and possibly in inflammatory cancer. Differential
effects of PP BL on normal and tumour cells indicate the presence of a biological target,
related also to cell proliferation, which will be the subject of our future work.
References:
1. Sedmak B, Kosi G (1997): Mycrocystins in Slovene freshwaters (central Europe) – first report. Natural
Toxins, 5: 64-73.
2. Grach-Pogrebinsky O, Sedmak B, Carmeli S (2003): Protease inhibitors from a Slovenian Lake Bled toxic
waterbloom of the cyanobacterium Planktothrix rubescens. Tetrahedron, 59: 8329-8336.
3. Pogrebinsky O, Sedmak B, Carmeli S (2004): Seco[D-Asp3] microcystin-RR and D-Asp3, D-Glu(OMe)6]
microcystin-RR, two new microcystins from a toxic water bloom of the cyanobacterium Planktothrix rubescens.
Journal of Natural Products, 67: 337-342.
4. Namikoshi M, Rinehart KL (1996): Bioactive compounds produced by cyanobacteria. Journal of Industrial
Microbiology, 17: 373-384.
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