ARTICLE Induction of vascular leakage through release of bradykinin and a novel kinin by cysteine proteinases from Staphylococcus aureus Takahisa Imamura,1 Sumio Tanase,2 Grzegorz Szmyd,3 Andrzej Kozik,4 James Travis,5 and Jan Potempa3,5 1Division of Molecular Pathology, Graduate School of Medical and Pharmaceutical Sciences and 2Department of Analytical Biochemistry, School of Health Sciences, Kumamoto University, Kumamoto 860-8556, Japan 3Department of Microbiology and 4Department of Analytical Biochemistry, Faculty of Biotechnology, Jagiellonian University, 31-007 Kraków, Poland 5Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 Staphylococcus aureus is a major pathogen of gram-positive septic shock and frequently is associated with consumption of plasma kininogen. We examined the vascular leakage (VL) activity of two cysteine proteinases that are secreted by S. aureus. Proteolytically active staphopain A (ScpA) induced VL in a bradykinin (BK) B2-receptor–dependent manner in guinea pig skin. This effect was augmented by staphopain B (SspB), which, by itself, had no VL activity. ScpA also produced VL activity from human plasma, apparently by acting directly on kininogens to release BK, which again was augmented significantly by SspB. Intravenous injection of ScpA into a guinea pig caused BK B2-receptor–dependent hypotension. ScpA and SspB together induced the release of leucyl-methionyl-lysyl-BK, a novel kinin with VL and blood pressure–lowering activities that are equivalent to BK. Collectively, these data suggest that production of BK and leucyl-methionyl-lysyl-BK by staphopains is a new mechanism of S. aureus virulence and bacterial shock. Therefore, staphopain-specific inhibitors and kinin- receptor antagonists could be used to treat this disease. CORRESPONDENCE Recent clinical studies revealed that gram- the final product of plasma kallikrein/kinin Takahisa Imamura: positive bacteria are as common as gram-nega- system activation which causes vascular leakage taka@ tive bacteria in causing sepsis (1, 2) that often (VL; reference 11) and leads to hypotension. kaiju.medic.kumamoto-u.ac.jp leads to septic shock, a condition with a high This bacterium has a high negative net surface Abbreviations used: BK, brady- mortality, despite improved antibiotic therapy charge because of the presence of cell wall te- kinin; BP, blood pressure; HK, and intensive care. The pathogenesis of septic ichoic acid and lipoteichoic acid (12), and can high molecular weight kinino- shock by gram-positive bacteria has not been activate the plasma kallikrein/kinin system as The Journal of Experimental Medicine gen; LK, low molecular weight kininogen; SBTI, soybean elucidated fully. However, the plasma levels of efficiently as LPS and lipid A from gram-nega- trypsin inhibitor; ScpA, stapho- the plasma kallikrein/kinin system components, tive bacteria in vitro (13). Thus, these cell wall pain A; SspB, staphopain B; factor XII, prekallikrein, and high molecular molecules also may activate the plasma kal- TBS, Tris-buffered saline; VL, vascular leakage. weight kininogen (HK), are low in patients who likrein/kinin system in S. aureus bacteremia. have sepsis (3–6); this indicates activation and However, heat-labile extracellular products of subsequent consumption of these components. S. aureus are far more potent than the cell wall The activation of the plasma kallikrein/kinin components as lethal factors in the mouse sepsis system in an animal bacteremia model causes model (14). lethal hypotension (7, 8); hence, plasma kal- In addition to enterotoxins and hemo- likrein/kinin system activation seems to con- lysins, S. aureus secretes several extracellular tribute to septic shock. proteinases (15) that may play a role in septic Staphylococcus aureus is the most frequently shock. The V8 proteinase can release kinin isolated pathogen in gram-positive sepsis (1, from HK. This activity is not abolished in the 9), which suggests that some factor from this presence of serine proteinase inhibitors (16); bacterium is associated with septic shock in- this suggests that other than the V8 proteinase, duction. In human plasma, S. aureus induces contaminating proteolytic activity may have the release of bradykinin (BK; reference 10), been responsible for kinin generation. Stapho- JEM © The Rockefeller University Press $8.00 1669 Vol. 201, No. 10, May 16, 2005 1669–1676 www.jem.org/cgi/doi/10.1084/jem.20042041 pains A and B (ScpA and SspB) are S. aureus–derived cys- teine proteinases. Their papainlike character has been inves- tigated thoroughly with respect to molecular structure and posttranslational processing of proenzymes and led to the generation of 21-kD mature proteinases (17–20). Therefore, we purified these two cysteine proteinases from S. aureus culture medium and examined their VL and blood pressure (BP)-lowering activities. ScpA, especially in concert with SspB, possessed strong VL activity and lowered BP. The re- sults indicate a new virulence mechanism in which stapho- pains liberate kinins, including a novel kinin that is released through alternative cleavage of kininogens. We believe that staphopains may be involved in septic shock that is caused by S. aureus infection. Figure 2. Leaked dye of each blue spot. (᭺), ScpA; (᭛), SspB; (᭝), BK; (᭡), BK (100 nM) ϩ SspB; (᭿), ScpA (60 nM) ϩ SspB; (᭹), ScpA treated with E-64 (50 ␮M). *P Ͻ 0.01 for ScpA 200 nM versus 60 nM or 600 nM; RESULTS for ScpA 60 nM ϩ SspB 60 nM versus ScpA 60 nM ϩ SspB 600 nM; and Induction of VL by ScpA for BK 10 nM versus 100 nM. **P Ͻ 0.03 for BK 100 nM versus 1000 nM. ScpA induced VL in a dose-dependent manner starting at an Inset, the effect of HOE140 on VL activity that was induced by stapho- enzyme concentration of 20 nM. In contrast to a linear in- pains, BK, or histamine. Guinea pigs were injected with HOE140 (10 nmol/kg crease of VL that is caused by exponentially increased doses body weight) 30 min before intradermal injection of samples. (White bars) of BK, the VL reaction that was triggered by ScpA injection Without HOE140 treatment; (black bars) with HOE140 treatment. A, ScpA increased steeply at higher enzyme concentrations (Figs. 1 300 nM; AϩB, ScpA 60 nM ϩ SspB 600 nM; BK, bradykinin 1 ␮M; HS, his- and 2). Because ScpA showed no VL activity when inacti- tamine 10 ␮M. Values are means Ϯ SD (n ϭ 3). *P Ͻ 0.01 for with versus vated by E-64, a cysteine proteinase inhibitor, the pro- without HOE140 treatment. teolytic activity of the enzyme is linked to production of VL activity (Figs. 1 and 2). Despite the lack of any significant VL activity, SspB increased ScpA-induced VL in a dose-depen- of staphopain VL activity on this receptor suggests kinin re- dent manner, whereas the proteinase exhibited no such ef- lease through activation of the factor XII-prekallikrein-kinin- fect on BK-induced VL (Fig. 2). HOE140, a BK B2 receptor ogen system by staphopains. At 600 nM, ScpA caused for- antagonist, strongly inhibited VL that was induced by ScpA, mation of a large blue spot on the guinea pig skin. This a mixture of ScpA and SspB, or BK, but not the reaction reaction contrasts with spots that were formed in response to that was caused by histamine (Fig. 2, inset). The dependency BK, which increased only slightly when the dose of BK was increased by three orders of magnitude (Fig. 1). To explain this phenomenon, we calculated the ratio of the blue spot area (in mm2) to the amount of dye that was extracted from the skin (in ␮g). Although higher doses of BK and gingipain R, a bacterial proteinase that is known to elicit strong VL re- action (21), increased dye extravasation, the ratio of the blue Figure 1. Induction of vascular permeability enhancement by staph- opains. 100 ␮l of staphopain A or B or BK was injected intradermally into a guinea pig that previously received Evans blue dye. a, ScpA (600 nM); b, ScpA (200 nM); c, ScpA (60 nM); d, ScpA (20 nM); e, ScpA (600 nM) treated Figure 3. Leaked area vs. leaked dye amount. The spot area (mm2) with E-64 (50 ␮M for 30 min); f, SspB (600 nM); g, bradykinin (1 ␮M); was divided by the dye amount (␮g) that was extracted from the spot. h, bradykinin (100 nM); i, bradykinin (10 nM); j, 10 mM tris-buffered saline. Values are means Ϯ SD (n ϭ 3). *P Ͻ 0.001. 1670 S. AUREUS PROTEINASES INCREASE VASCULAR LEAKAGE | Imamura et al. ARTICLE Fig. 3). kininogen-deficient plasma (Fig. 4, inset). This suggested the ;2.5ف) spot area to the amount of dye was constant In contrast, in the case of ScpA-induced VL, the ratio was direct action of ScpA on kininogen. To confirm this, we in- much greater and dependent on enzyme concentration (Fig. vestigated the ScpA-dependent VL generation in kininogen- 3). This suggests an excessive spread of leaked plasma which deficient plasma that was supplemented with physiologic carried Evans blue to the extravascular space in the connec- concentrations of kininogens (22). ScpA induced VL activity tive tissue of the guinea pig skin after ScpA injection. from HK reconstituted kininogen-deficient plasma, which was increased further by the addition of low molecular Production of VL activity from human plasma by ScpA weight kininogen (LK) to a level of the normal plasma con- ScpA generated VL activity from normal human plasma in a centration (Fig. 4, inset). Together, these data indicate that dose- and activity-dependent manner when incubated for both kininogens are the major targets of staphopains, and ac- only 5 min (Fig. 4). SspB did not produce VL activity by tivation of factor XII or prekallikrein contributes negligibly itself; however, the enzyme significantly increased ScpA- to the VL activity production.