Modulation of Adhesion Molecules Expression by Different Metalloproteases Isolated from Bothrops Snakes

Snake venom metalloproteinases (SVMP) are involved in local inflammatory reactions observed after snakebites. Based on domain composition, they are classified as PI (pro-domain + proteolytic domain), PII (PI + disintegrin-like domains), or PIII (PII + cysteine-rich domains). Here, we studied the role of different SVMPs domains in inducing the expression of adhesion molecules at the microcirculation of the cremaster muscle of mice. We used Jararhagin (Jar)-a PIII SVMP with intense hemorrhagic activity, and Jar-C-a Jar devoid of the catalytic domain, with no hemorrhagic activity, both isolated from B. jararaca venom and BnP-1-a weakly hemorrhagic P1 SVMP from B. neuwiedi venom. Toxins (0.5 µg) or PBS (100 µL) were injected into the scrotum of mice, and 2, 4, or 24 h later, the protein and gene expression of CD54 and CD31 in the endothelium, and integrins (CD11a and CD11b), expressed in leukocytes were evaluated. Toxins induced significant increases in CD54, CD11a, and CD11b at the initial time and a time-related increase in CD31 expression. In conclusion, our results suggest that, despite differences in hemorrhagic activities and domain composition of the SVMPs used in this study, they behave similarly to the induction of expression of adhesion molecules that promote leukocyte recruitment.

Jararhagin disruption of endothelial cell anchorage is enhanced in collagen enriched matrices

Hemorrhage is one of the most striking effects of bites by viper snakes resulting in fast bleeding and ischemia in affected tissues. Snake venom metalloproteinases (SVMPs) are responsible for hemorrhagic activity, but the mechanisms involved in SVMP-induced hemorrhage are not entirely understood and the study of such mechanisms greatly depends on in vivo experiments. In vivo, hemorrhagic SVMPs accumulate on basement membrane (BM) of venules and capillary vessels allowing the hydrolysis of collagen IV with consequent weakness and rupture of capillary walls. These effects are not reproducible in vitro with conventional endothelial cell cultures. In this study we used two-dimension (2D) or three-dimension (3D) cultures of HUVECs on matrigel and observed the same characteristics as in ex vivo experiments: only the hemorrhagic toxin was able to localize on surfaces or internalize endothelial cells in 2D cultures or in the surface of tubules formed on 3D cultures. The contribution of matrigel, fibronectin and collagen matrices in jararhagin-induced endothelial cell damage was then analyzed. Collagen and matrigel substrates enhanced the endothelial cell damage induced by jararhagin allowing toxin binding to focal adhesions, disruption of stress fibers, detachment and apoptosis. The higher affinity of jararhagin to collagen than to fibronectin explains the localization of the toxin within BM. Moreover, once located in BM, interactions of jararhagin with α2β1 integrin would favor its localization on focal adhesions, as observed in our study. The accumulation of toxin in focal adhesions, observed only in cells grown in collagen matrices, would explain the enhancement of cell damage in these matrices and reflects the actual interaction among toxin, endothelial cells and BM components that occurs in vivo and results in the hemorrhagic lesions induced by viper venoms.

Jararhagin-induced mechanical hyperalgesia depends on TNF-α, IL-1β and NFκB in mice

Jararhagin is a hemorrhagic metalloprotease from Bothrops jararaca snake venom. The hyperalgesic mechanisms of jararhagin were investigated focusing on the role of proinflammatory cytokines (TNF-α and IL-1β) and the transcription factor NFκB. Intraplantar administration of jararhagin (1, 10, 100 and 1000 ng/paw) induced mechanical hyperalgesia, and increased TNF-α levels at 1, 3 and 5 h, and IL-1β levels at 0.5, 1 and 3 h after its injection in the paw tissue. Pre-treatment with morphine (2, 6, 12 μg/paw) inhibited jararhagin-induced mechanical hyperagesia. The systemic or local pre-treatment with etanercept (10 mg/kg and 100 μg/paw) and IL-1ra (30 mg/kg and 100 pg/paw) inhibited jararhagin-induced mechanical hyperalgesia. Co-administration of jararhagin (0.1 ng/paw) and TNF-α (0.1 pg/paw) or jararhagin (0.1 ng/paw) and IL-1β (1 pg/paw) enhanced the mechanical hyperalgesia. The systemic or local pre-treatment with PDTC (NFκB inhibitor; 100 mg/kg and 100 μg/paw) inhibited jararhagin-induced mechanical hyperalgesia as well as PDTC decreased the jararhagin-induced production of TNF-α and IL-1β. Thus, these data demonstrate the involvement of pro-inflammatory cytokines TNF-α and IL-1β and nuclear transcription factor NFκB in jararhagin-induced mechanical hyperalgesia indicating that targeting these mechanisms might contribute to reduce the pain induced by B. jararaca snake venom.

Diversity of metalloproteinases in Bothrops neuwiedi snake venom transcripts: evidences for recombination between different classes of SVMPs

Background

Snake venom metalloproteinases (SVMPs) are widely distributed in snake venoms and are versatile toxins, targeting many important elements involved in hemostasis, such as basement membrane proteins, clotting proteins, platelets, endothelial and inflammatory cells. The functional diversity of SVMPs is in part due to the structural organization of different combinations of catalytic, disintegrin, disintegrin-like and cysteine-rich domains, which categorizes SVMPs in 3 classes of precursor molecules (PI, PII and PIII) further divided in 11 subclasses, 6 of them belonging to PII group. This heterogeneity is currently correlated to genetic accelerated evolution and post-translational modifications.

Results

Thirty-one SVMP cDNAs were full length cloned from a single specimen of Bothrops neuwiedi snake, sequenced and grouped in eleven distinct sequences and further analyzed by cladistic analysis. Class P-I and class P-III sequences presented the expected tree topology for fibrinolytic and hemorrhagic SVMPs, respectively. In opposition, three distinct segregations were observed for class P-II sequences. P-IIb showed the typical segregation of class P-II SVMPs. However, P-IIa grouped with class P-I cDNAs presenting a 100% identity in the 365 bp at their 5' ends, suggesting post-transcription events for interclass recombination. In addition, catalytic domain of P-IIx sequences segregated with non-hemorrhagic class P-III SVMPs while their disintegrin domain grouped with other class P-II disintegrin domains suggesting independent evolution of catalytic and disintegrin domains. Complementary regions within cDNA sequences were noted and may participate in recombination either at DNA or RNA levels. Proteins predicted by these cDNAs show the main features of the correspondent classes of SVMP, but P-IIb and P-IIx included two additional cysteines cysteines at the C-termini of the disintegrin domains in positions not yet described.

Conclusions

In B. neuwiedi venom gland, class P-II SVMPs were represented by three different types of transcripts that may have arisen by interclass recombination with P-I and P-III sequences after the divergence of the different classes of SVMPs. Our observations indicate that exon shuffling or post-transcriptional mechanisms may be driving these recombinations generating new functional possibilities for this complex group of snake toxins.

Different regions of the class P-III snake venom metalloproteinase jararhagin are involved in binding to alpha2beta1 integrin and collagen

SVMPs are multi-domain proteolytic enzymes in which disintegrin-like and cysteine-rich domains bind to cell receptors, plasma or ECM proteins. We have recently reported that jararhagin, a P-III class SVMP, binds to collagen with high affinity through an epitope located within the Da-disintegrin sub-domain. In this study, we evaluated the binding of jararhagin to alpha(2)beta(1) integrin (collagen receptor) using monoclonal antibodies and recombinant jararhagin fragments. In solid phase assays, binding of jararhagin to alpha(2)beta(1) integrin was detectable from concentrations of 20 nM. Using recombinant fragments of jararhagin, only fragment JC76 (residues 344-421), showed a significant binding to recombinant alpha(2)beta(1) integrin. The anti-jararhagin monoclonal antibody MAJar 3 efficiently neutralised binding of jararhagin to collagen, but not to recombinant alpha(2)beta(1) integrin nor to cell-surface-exposed alpha(2)beta(1) integrin (alpha(2)-K562 transfected cells and platelets). The same antibody neutralised collagen-induced platelet aggregation. Our data suggest that jararhagin binding to collagen and alpha(2)beta(1) integrin occurs by two independent motifs, which are located on disintegrin-like and cysteine-rich domains, respectively. Moreover, toxin binding to collagen appears to be sufficient to inhibit collagen-induced platelet aggregation.

Collagen binding is a key factor for the hemorrhagic activity of snake venom metalloproteinases

Snake venom metalloproteinases (SVMPs) are multifunctional enzymes involved in several symptoms following snakebite, such as severe local hemorrhage. Multidomain P-III SVMPs are strongly hemorrhagic, whereas single domain P-I SVMPs are not. This indicates that disintegrin-like and cysteine-rich domains allocate motifs that enable catalytic degradation of ECM components leading to disruption of capillary vessels. Interestingly, some P-III SVMPs are completely devoid of hemorrhagic activity despite their highly conserved disintegrin-like and cysteine-rich domains. This observation was approached in the present study by comparing the effects of jararhagin, a hemorrhagic P-III SVMP, and berythractivase, a pro-coagulant and non-hemorrhagic P-III SVMP. Both toxins inhibited collagen-induced platelet aggregation, but only jararhagin was able to bind to collagen I with high affinity. The monoclonal antibody MAJar 3, that neutralizes the hemorrhagic effect of Bothrops venoms and jararhagin binding to collagen, did not react with berythractivase. The three-dimensional structures of jararhagin and berythractivase were compared to explain the differential binding to collagen and MAJar 3. Thereby, we pinpointed a motif within the Da disintegrin subdomain located opposite to the catalytic domain. Jararhagin binds to both collagen I and IV in a triple helix-dependent manner and inhibited in vitro fibrillogenesis. The jararhagin-collagen complex retained the catalytic activity of the toxin as observed by hydrolysis of fibrin. Thus, we suggest that binding of hemorrhagic SVMPs to collagens I and IV occurs through a motif located in the Da subdomain. This allows accumulation of toxin molecules at the site of injection, close to capillary vessels, where their catalytic activity leads to a local hemorrhage. Toxins devoid of this motif would be more available for vascular internalization leading to systemic pro-coagulant effects. This reveals a novel function of the disintegrin domain in hemorrhage formation.

BnP1, a novel P-I metalloproteinase from Bothrops neuwiedi venom: biological effects benchmarking relatively to jararhagin, a P-III SVMP

Snake venom metalloproteinases (SVMPs) have been extensively studied and their effects associated with the local bleeding observed in human accidents by viper snakes. Representatives of P-I and P-III classes of SVMPs similarly hydrolyze extracellular matrix proteins or coagulation factors while only P-III SVMPs induce significant hemorrhage in experimental models. In this work, the effects of P-I and P-III SVMPs on plasma proteins and cultures of muscle and endothelial cells were compared in order to enlighten the mechanisms involved in venom-induced hemorrhage. To reach this comparison, BnP1 was isolated from B. neuwiedi venom and used as a weakly hemorrhagic P-I SVMPs and jararhagin was used as a model of potently hemorrhagic P-III SVMP. BnP1 was isolated by size exclusion and anion-exchange chromatographies, showing apparent molecular mass of approximately 24kDa and sequence similarity with other members of SVMPs, which allowed its classification as a group P-I SVMP. The comparison of local effects induced by SVMPs showed that BnP1 was devoid of significant myotoxic and hemorrhagic activities and jararhagin presented only hemorrhagic activity. BnP1 and jararhagin were able to hydrolyze fibrinogen and fibrin, although the latter displayed higher activity in both systems. Using HUVEC primary cultures, we observed that BnP1 induced cell detachment and a decrease in the number of viable endothelial cells in levels comparable to those observed by treatment with jararhagin. Moreover, both BnP1 and jararhagin induced apoptosis in HUVECs while only a small increase in LDH supernatant levels was observed after treatment with jararhagin, suggesting that the major mechanism involved in endothelial cell death is apoptosis. Jararhagin and BnP1 induced little effects on C2C12 muscle cell cultures, characterized by a partial detachment 24h after treatment and a mild necrotic effect as evidenced by a small increase in the supernatants LDH levels. Taken together, our data show that P-I and P-III SVMPs presented comparable effects except for the hemorrhagic activity, suggesting that hydrolysis of coagulation factors or damage to endothelial cells are not sufficient for induction of local bleeding.

Importance of jararhagin disintegrin-like and cysteine-rich domains in the early events of local inflammatory response

Jararhagin is a multi-domain SVMP from Bothrops jararaca venom comprising catalytic, disintegrin-like and cysteine-rich domains, which cause a local reaction manifested by hemorrhage, edema, cytokine release and inflammatory cell recruitment. In this study, the importance of disintegrin-like/cysteine-rich domains of jararhagin was addressed by analyzing the effects of jararhagin-C, which lacks the catalytic domain, in induction of leukocyte rolling and release of pro-inflammatory cytokines. Jararhagin-C was isolated from B. jararaca venom conserving the same ability of complete jararhagin molecule in inhibiting collagen-induced platelet-aggregation. Treatment of trans-illuminated cremaster muscle in vivo with jararhagin-C increased number of rolling leukocytes (approximately 250%) in post-capillary venules in all periods analyzed, without interfering with microvasculature haemodynamic, like vessel diameter, the erythrocyte speed or the blood flow rate. The release of pro-inflammatory cytokines TNF-alpha, IL-1beta and IL-6 was significantly enhanced in the local of jararhagin-C injection, showing the maximum levels in periods between 2 and 4 h after treatment. Besides the action of jararhagin-C, the presence of the inactivated catalytic domain in o-phenanthrolin-treated jararhagin was related to a higher increase in the number of rolling leukocytes. Moreover, the levels of IL-6 and IL-1beta induced by catalytically active jararhagin were higher than those induced by jararhagin-C. In conclusion, our findings suggest that the disintegrin-like/cysteine-rich domains of jararhagin are sufficient to locally activate the early events of an acute inflammatory response as leukocyte rolling and pro-inflammatory cytokine release and this action may add to the effect of catalysis, which enhances the primary cell activation.

Jararhagin, a snake venom metalloproteinase, induces a specialized form of apoptosis (anoikis) selective to endothelial cells

Jararhagin is a snake venom metalloproteinase (SVMP) from Bothrops jararaca involved in several hemostatic and inflammatory disorders that occur in human envenomings. In this study, we evaluated the effect of jararhagin on endothelial cells (tEnd). The exposure of tEnd to jararhagin (20 and 40microg/ml) resulted in apoptosis with activation of pro-caspase-3 and alterations in the ratio between Bax/Bcl-xL. We observed that apoptosis was followed by decrease of cell viability and the loss of cell adhesion. Jararhagin induced changes in cell shape with a decrease in cell spreading, rounding up and detachment. This was accompanied by a rearrangement of actin network and a decrease in FAK association to actin and in tyrosine phosphorylated proteins. Morphological alterations and apoptosis were abolished when jararhagin catalytic activity was inhibited, indicating the importance of catalysis. Treatment of murine peritoneal adherent cells or fibroblasts with jararhagin did not result in apoptosis. The data indicate that the pro-apoptotic effect of jararhagin is selective to endothelial cells, interfering with the adhesion mechanisms and inducing anoikis. The present model might be useful for the study of the relationships between the architectural changes in the cytoskeleton and the complex phenomenon named anoikis.

Importance of metalloproteinases and macrophages in viper snake envenomation-induced local inflammation

The inflammatory action of jararhagin, a hemorrhagic metalloproteinase from Bothrops jararaca venom, was studied in mice using dorsal air pouches. The injection of the toxin in 6-day-old air pouches resulted in a leukocyte accumulation comparable to that induced by LPS and whole venom. Polymorphonuclear and mononuclear cells were present in this infiltrate, with a predominance of neutrophils. Treatment of jararhagin with 1,10-phenantroline abolished its proteolytic activity and reduced the pro-inflammatory effect in approximately 50%. Cell influx was not observed when jararhagin was injected into 1-hr air pouches devoid of macrophages, except when it was injected together with 10(6) syngeneic peritoneal macrophages. Supernatants of macrophages stimulated in vitro with jararhagin did not induce leukocyte influx in 1-hr air pouches; the influx occurred after injection of the pellets of stimulated cultures. In summary, jararhagin is an important pro-inflammatory component of B. jararaca venom, and its activity is dependent upon the proteolytic activity and the presence of macrophages.

The effect of jararhagin, a metalloproteinase from Bothrops jararaca venom, on pro-inflammatory cytokines released by murine peritoneal adherent cells

The release of pro-inflammatory cytokines (IL-1beta, IL-6 and TNF-alpha) from murine peritoneal adherent cells (MPAC) was studied after exposure to jararhagin, a metalloproteinase/disintegrin isolated from Bothrops jararaca venom. MPACs were treated with LPS (lipopolysaccharide), jararhagin, or EDTA-inactivated jararhagin for up to 24h. Following incubation, the culture supernatant was assayed by ELISA for the presence of cytokines, while the cells were analysed for viability and cytokine mRNA expression. The cells exposed to native jararhagin released TNF-alpha and IL-1beta after 4 and 24h respectively. When MPACs were exposed to Jararhagin treated with EDTA, TNF-alpha and IL-1beta production was sustained throughout the culture period and IL-6 production was observed. TNF-alpha, IL-6 and IL-1beta mRNA were detected 4h after stimulation with either native or EDTA-treated jararhagin. Addition of jararhagin to LPS stimulated cells resulted in a dramatic decrease in the release of IL-6 and TNF-alpha. RT-PCR showed that this inhibition does not occur at the transcriptional level and further experiments showed that jararhagin degraded soluble cytokines by proteolytic activity. This study suggests that jararhagin induces TNF-alpha, IL-1beta and IL-6 expression, which may be rapidly degraded by its proteolytic activity.

Toxicity and immunogenicity of Crotalus durissus terrificus venom treated with different doses of gamma rays

Crotalus durissus terrificus venom (CDT venom) was irradiated with four different doses of gamma rays (2, 3, 5 and 10 kGy) from a 60Co source and their structural, toxic and immunogenic properties were analysed. Venom irradiated with 2 and 3 kGy were, respectively, 2.7 and 13.5 times less toxic than the native one, whereas the 5 or 10 kGy irradiated venom were at least 100 times less toxic than nonirradiated venom. Irradiated venom with all doses were immunogenic and the antibodies elicited by them were able to recognise the native venom in ELISA. However the toxoid produced with 2 kGy irradiation dose had its immunogenicity improved. Antisera raised against this toxoid had a higher neutralising capacity than those produced against the native venom. Irradiation of venom with 2 kGy dose was the most effective to inactivate the CDT venom toxicity and improve its immunogenicity.