Kinin release from human kininogen by 10 aspartic proteases produced by pathogenic yeast Candida albicans

Abstract

BackgroundCandida albicans yeast produces 10 distinct secreted aspartic proteases (Saps), which are some of the most important virulence factors of this pathogenic fungus. One of the suggested roles of Saps is their deregulating effect on various proteolytic cascades that constitute the major homeostatic systems in human hosts, including blood coagulation, fibrinolysis, and kallikrein-kinin systems. This study compared the characteristics of the action of all 10 Saps on human kininogens, which results in generating proinflammatory bradykinin-related peptides (kinins).ResultsRecombinant forms of Saps, heterologously overexpressed in Pichia pastoris were applied. Except for Sap7 and Sap10, all Saps effectively cleaved the kininogens, with the highest hydrolytic activity toward the low-molecular-mass form (LK). Sap1–6 and 8 produced a biologically active kinin—Met-Lys-bradykinin—and Sap3 was exceptional in terms of the kinin-releasing yield (>60% LK at pH 5.0 after 24 hours). Des-Arg1-bradykinin was released from LK by Sap9 at a comparably high yield, but this peptide was assumed to be biologically inactive because it was unable to interact with cellular B2-type kinin receptors. However, the collaborative actions of Sap9 and Sap1, −2, −4–6, and −8 on LK rerouted kininogen cleavage toward the high-yield release of the biologically active Met-Lys-bradykinin.ConclusionsOur present results, together with the available data on the expression of individual SAP genes in candidal infection models, suggest a biological potential of Saps to produce kinins at the infection foci. The kinin release during candidiasis can involve predominant and complementary contributions of two different Sap3- and Sap9-dependent mechanisms.

A Role for Bradykinin Signaling in Chronic Vulvar Pain

“…Due to its association with IL-6 release and the link between IL-6 and LPV pain, inhibiting bradykinin sensing might be a possible target for new LPV therapeutics. At present, several bradykinin receptor inhibitors are currently being evaluated in clinical trials, which could lead to a faster clinical translation 4, 5, 39, 54 .…”

“…We became interested in bradykinin because of its inflammatory and pain-inducing qualities 56 and the observation that Candida , which has been implicated in vulvar pain, may play a role in exacerbating the responses to bradykinin by generating locally elevated concentrations of bradykinin 9, 10, 35, 36, 39, 57 . Candida species produce serine aspartyl proteases that cleave human HMW kininogens, which is believed vital to pathogenesis and aids in tissue invasion by C. albicans 9, 10, 35, 39, 57 .…”

“…Candida species produce serine aspartyl proteases that cleave human HMW kininogens, which is believed vital to pathogenesis and aids in tissue invasion by C. albicans 9, 10, 35, 39, 57 . Therefore, we hypothesized that bradykinin may also play important roles in inflammation and pain within the vulvar vestibule.…”

Extracellular proteinases of Candida species pathogenic yeasts

“…The latter mechanism was analyzed in detail for purified C. albicans Sap2, C. parapsilosis Sapp1 and Sapp2 and all recombinant C. albicans Saps, except for Sap7 . For all of these Saps, a low‐molecular form of human kininogen (LK), rather than HK, was an optimal substrate and an atypical kinin—Met‐Lys‐bradykinin, which has a biological activity equivalent to that of bradykinin—was released at the highest yield by Sap3 and mixtures of Sap9 with any of the other Saps . It was hypothesized that the cooperative degradation of kininogens by several Saps can be exploited by C. albicans to produce an optimal amount of kinins at sites of infection …”

Experimental Models of Vaginal Candidiasis and Their Relevance to Human Candidiasis

“…Some authors, using a variant mouse model, have reported the induction of Th17 and of a particular subset of CD4 T cells and have associated the production of cytokines interleukin-17A (IL-17A) and IL-22, beta-defensin, and anti-Candida defensive peptides with at least partial control of the infection, with some similarity to oral candidiasis (11,27,28). More recently, the activation of a typical Nod-like receptor protein 3 (NLRP3) inflammasome-mediated cytokine response has been reported to occur (29)(30)(31), and Sap production by C. albicans has been associated with vaginal inflammation, indicating that one or more of these enzymes could indeed be the direct or indirect cause of inflammasome activation in the epithelial cells (29,30,32). Interestingly, the data on the relevant pathogenetic role exerted by those enzymes in the mouse model are probably the only data that largely match those reported in the rat model and in women (see above), hence collectively suggesting that C. albicans Sap could indeed play a dominant pathogenic role in vaginal candidiasis.…”