Abstract
There is an urgent need to develop safe, effective, dual-purpose contraceptive agents that combine the prevention of pregnancy with protection against sexually transmitted diseases. Here we report the identification of a group of compounds that on contact with human spermatozoa induce a state of “spermostasis,” characterized by the extremely rapid inhibition of sperm movement without compromising cell viability. These spermostatic agents were more active and significantly less toxic than the reagent in current clinical use, nonoxynol 9, giving therapeutic indices (ratio of spermostatic to cytotoxic activity) that were orders of magnitude greater than this traditional spermicide. Although certain compounds could trigger reactive oxygen species generation by spermatozoa, this activity was not correlated with spermostasis. Rather, the latter was associated with alkylation of two major sperm tail proteins that were identified as A Kinase-Anchoring Proteins (AKAP3 and AKAP4) by mass spectrometry. As a consequence of disrupted AKAP function, the abilities of cAMP to drive protein kinase A-dependent activities in the sperm tail, such as the activation of SRC and the consequent stimulation of tyrosine phosphorylation, were suppressed. Furthermore, analysis of microbicidal activity using Chlamydia muridarum revealed powerful inhibitory effects at the same low micromolar doses that suppressed sperm movement. In this case, the microbicidal action was associated with alkylation of Major Outer Membrane Protein (MOMP), a major chlamydial membrane protein. Taken together, these results have identified for the first time a novel set of cellular targets and chemical principles capable of providing simultaneous defense against both fertility and the spread of sexually transmitted disease.
Footnotes
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This work was supported by the Australian National Health and Medical Research Council [Grant 252441] and the Australian Research Council Centre of Excellence in Biotechnology and Development.
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ABBREVIATIONS: STD, sexually transmitted disease; PKA, protein kinase A; AKAP, A kinase-anchoring protein; MOMP, major outer membrane protein; N9, nonoxynol 9; BWW, Biggers, Whitten and Whittingham medium; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; DHE, dihydroethidium; DTT, dithiothreitol; pCMBS, p-chloromercuribenzene sulfonic acid; Ptx, pentoxifylline; dbcAMP, dibutyryl cyclic adenosine monophosphate; PBS, phosphate-buffered saline; BSA, bovine serum albumin; MALDI-TOF, matrix-assisted-laser desorption-ionization-time-of-flight mass spectrometer; MBP, maltose binding protein; TI, therapeutic index; ROS, reactive oxygen species; Et, ethidium; 2OHEt, 2-hydroxyethidium; LUMO, lowest unoccupied molecular orbital; p-BQ, p-benzoquinone; BM, bismaleimide; p-NQ, p-naphthoquinone; RT, room temperature; PAGE, polyacrylamide gel electrophoresis; IFU, inclusion forming unit; SOD, superoxide dismutase.
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The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
- Accepted March 31, 2009.
- Received November 22, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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