Potential involvement of gelatinases and their inhibitors in Mannheimia haemolytica pneumonia in cattle

Identification, Biochemical Characterization, and In Vivo Detection of a Zn-Metalloprotease with Collagenase Activity from Mannheimia haemolytica A2

Respiratory diseases in ruminants are a main cause of economic losses to farmers worldwide. Approximately 25% of ruminants experience at least one episode of respiratory disease during the first year of life. Mannheimia haemolytica is the main etiological bacterial agent in the ruminant respiratory disease complex. M. haemolytica can secrete several virulence factors, such as leukotoxin, lipopolysaccharide, and proteases, that can be targeted to treat infections. At present, little information has been reported on the secretion of M. haemolytica A2 proteases and their host protein targets. Here, we obtained evidence that M. haemolytica A2 proteases promote the degradation of hemoglobin, holo-lactoferrin, albumin, and fibrinogen. Additionally, we performed biochemical characterization for a specific 110 kDa Zn-dependent metalloprotease (110-Mh metalloprotease). This metalloprotease was purified through ion exchange chromatography and characterized using denaturing and chaotropic agents and through zymography assays. Furthermore, mass spectrometry identification and 3D modeling were performed. Then, antibodies against the 110 kDa-Mh metalloprotease were produced, which achieved great inhibition of proteolytic activity. Finally, the antibodies were used to perform immunohistochemical tests on postmortem lung samples from sheep with suggestive histology data of pneumonic mannheimiosis. Taken together, our results strongly suggest that the 110-Mh metalloprotease participates as a virulence mechanism that promotes damage to host tissues.

The Effects of Ursolic Acid Treatment on Immunopathogenesis Following Mannheimia haemolytica Infections

Bovine respiratory disease complex (BRDC) is a costly economic and health burden for the dairy and feedlot cattle industries. BRDC is a multifactorial disease, often involving viral and bacterial pathogens, which makes it difficult to effectively treat or vaccinate against. Mannheimia haemolytica (MH) are common commensal bacteria found in the nasopharynx of healthy cattle; however, following environmental and immunological stressors, these bacteria can rapidly proliferate and spread to the lower respiratory tract, giving rise to pneumonic disease. Severe MH infections are often characterized by leukocyte infiltration and dysregulated inflammatory responses in the lungs. IL-17A is thought to play a key role in this inflammatory response by inducing neutrophilia, activating innate and adaptive immune cells, and further exacerbating lung congestion. Herein, we used a small molecule inhibitor, ursolic acid (UA), to suppress IL-17A production and to determine the downstream impact on the immune response and disease severity following MH infection in calves. We hypothesized that altering IL-17A signaling during MH infections may have therapeutic effects by reducing immune-mediated lung inflammation and improving disease outcome. Two independent studies were performed (Study 1 = 32 animals and Study 2 = 16 animals) using 4-week-old male Holstein calves, which were divided into 4 treatment group including: (1) non-treated and non-challenged, (2) non-treated and MH-challenged, (3) UA-treated and non-challenged, and (4) UA-treated and MH-challenged. Based on the combined studies, we observed a tendency (p = 0.0605) toward reduced bacterial burdens in the lungs of UA-treated animals, but did not note a significant difference in gross (p = 0.3343) or microscopic (p = 0.1917) pathology scores in the lungs. UA treatment altered the inflammatory environment in the lung tissues following MH infection, reducing the expression of IL-17A (p = 0.0870), inflammatory IL-6 (p = 0.0209), and STAT3 (p = 0.0205) compared to controls. This reduction in IL-17A signaling also appeared to alter the downstream expression of genes associated with innate defenses (BAC5, DEFB1, and MUC5AC) and lung remodeling (MMP9 and TIMP-1). Taken together, these results support our hypothesis that IL-17A signaling may contribute to lung immunopathology following MH infections, and further understanding of this inflammatory pathway could expand therapeutic intervention strategies for managing BRDC.

Serum proteins and lipids in mild form of calf bronchopneumonia: candidates for reliable biomarkers

Calf bronchopneumonia is complex multifactorial disease and for its accurate diagnosis and therapy, besides clinical examination, microbiologic, hematologic and biochemical analyses could be necessary. In general, additional analyses are not implemented, mainly because the disease biomarkers are not defined.

To establish which analysis might be useful for determining the severity of the disease, we analyzed 23 three-month old calves with mild clinical signs of bronchopneumonia and 15 age-matched healthy calves. Pasteurella multocida was isolated from deep nasal swabs of diseased calves. Peripheral blood erythrocyte and leukocyte count of bronchopneumonic and healthy calves showed no difference. Serum proteins, lipoproteins and lipids were analyzed with spectrophotometry, agarose gel electrophoresis, non-reducing SDS-PAGE, gel zymography, and thin-layer chromatography. The bronchopneumonic calves had an increased level of circulating immune complexes and α globulins, which contain some of the positive acute phase proteins. In diseased calves the increased concentration of total γ globulins (IgG), due to an increased concentration of anionic γ globulins (predominately IgG1), was detected. The increased concentration of anionic γ globulins followed by increased concentration of transferrin (negative acute phase protein) and HDL cholesterol, decreased concentration of LDL-cholesterol, unchanged activity of matrix metalloproteases and leukocyte counts might reflect the obvious absence of generalized inflammation. A positive correlation was found between the acquired results and the appearance of mild clinical signs. Therefore, we believe that the parameters analyzed in the peripheral blood could be applied as reliable disease markers to distinguish between severe (inflammatory) and mild forms of calf bronchopneumonia and to predict a better outcome for these calves.

Invited review: Relationship between cattle transport, immunity and respiratory disease

The association between transportation and the occurrence of the bovine respiratory disease complex (BRDC) has long been recognised. Many hypotheses regarding this association have been declared through the past decades, and it is agreed upon by most researchers that the multiple stressors that calves experience during transportation result in an overall immunosuppression that allows the respiratory tract to be invaded by numerous opportunistic pathogens. Furthermore, the innate immune cells, neutrophils, may be trapped in a paradox whereby their crucial defence and pathogen-killing activities are counteracted by excessive inflammation and tissue damage that may exacerbate disease, including the BRDC. Neutrophilia in response to glucocorticoids has been attributed to an influx of immature neutrophils newly released from the bone marrow, a decrease in neutrophil margination along endothelial walls, and a decrease in neutrophil apoptosis. Several of these explanations have been confirmed by altered expression of genes and proteins important for neutrophil margination and apoptosis.

Effect of the synthetic Toll-like receptor ligands LPS, Pam3CSK4, HKLM and FSL-1 in the function of bovine polymorphonuclear neutrophils

Toll-like receptors (TLR) are a family of pattern recognition receptors that sense microbial associated molecular patterns (MAMP) such as microbial membrane components and nucleic acids of bacterial origin. Polymorphonuclear neutrophils (PMN) are the first cell of the innate immune system to arrive at the site of infection or injury and elicit oxidative and non-oxidative microbicidal mechanisms. Observations in human and mouse suggest that TLR ligands can induce direct responses in PMN. So far, there is no information of the effect of synthetic TLR ligands on the response of bovine PMN. The objective of this study was to evaluate the functional response of bovine PMN incubated with four synthetic TLR ligands: ultrapure LPS (TLR4), Pam(3)CSK(4) (TLR2/1), HKLM (TLR2) and FSL-1 (TLR2/6). The results show that all the ligands increment cells size as identified by changes in the FSC-SSC as part of the flow cytometric analysis. Interestingly, only Pam(3)CSK(4) consistently induced a calcium influx, increased ROS production and secretion of gelatinase granules, whereas no response was seen using other ligands. Furthermore, exposure of bovine PMN to ultrapure LPS, Pam(3)CSK(4), HKLM or FSL-1 for 24 hours did not impact on apoptosis of these cells. Our data provide evidence for a selective response of bovine PMNs to TLR ligands.

Serum concentrations of haptoglobin and haptoglobin-matrix metalloproteinase 9 (Hp-MMP 9) complexes of bovine calves in a bacterial respiratory challenge model

Background

Serum haptoglobin (Hp) and haptoglobin matrix metalloproteinase 9 complexes (Hp-MMP 9) have been identified as biomarkers with diagnostic potential in cattle with conditions resulting in an acute inflammatory response. The purpose of this study was to evaluate potential diagnostic applications of serum Hp and Hp-MMP 9 concentrations in calves with BRD and establish a timeline for their detection in calves experimentally challenged with Bibersteinia trehalosi and Mannheimia haemolytica. Thirty-five cross bred dairy calves were inoculated via tracheal catheterization with either a PCR confirmed leukotoxin negative B. trehalosi isolate, a PCR confirmed leukotoxin positive B. trehalosi isolate, a Mannheimia haemolytica isolate, a combination of leukotoxin negative B. trehalosi and M. haemolytica, or a negative control. Serum samples were collected throughout the study. Calves were euthanized and necropsy performed on day 10 post inoculation.

Results

M. haemolytica inoculated calves had increased lung involvement. Serum Hp and Hp- MMP 9 concentrations were elevated compared to the other treatment groups. Increases in serum Hp and Hp-MMP 9 concentrations for the M. haemolytica group were significantly different from other study groups on day 7 of the study. B. trehalosi inoculated calves did not have increased lung involvement compared to control calves, but the leukotoxin positive B. trehalosi group demonstrated increased serum Hp-MMP 9 concentrations from day 3 to the end of the study compared to the pre-inoculation concentrations.

Conclusion

Serum Hp-MMP 9 concentration is a useful diagnostic tool for detecting early pulmonary inflammation in calves challenged with B. trehalosi and M. haemolytica. Serum Hp-MMP 9 may also be a useful tool in detecting subclinical pulmonary inflammation in challenged calves.

Histopathological analogies in chronic pulmonary lesions between cattle and humans: basis for an alternative animal model

Most of the natural cases of pneumonia in feedlot cattle are characterized by a longer clinical course due to chronic lung lesions. Microscopically, these lesions include interstitial fibroplasia, bronchitis, bronchiectasis, bronchiolitis obliterans, and epithelial metaplasia of the airways. Herein, the aim was to review, under a medical perspective, the pathologic mechanisms operating in these chronic pneumonic lesions in calves. Based on the similarities of these changes to those reported in bronchiolitis obliterans/organising pneumonia (BO/OP) and chronic obstructive pulmonary disease (COPD) in human beings, calves are proposed as an alternative animal model.

D-lactic acid interferes with the effects of platelet activating factor on bovine neutrophils

D-lactic acidosis occurs in ruminants, such as cattle, with acute ruminal acidosis caused by ingestion of excessive amounts of highly fermentable carbohydrates. Affected animals show clinical signs similar to those of septic shock, as well as acute laminitis and liver abscesses. It has been proposed that the inflammatory response and susceptibility to infection could both be caused by the inhibition of phagocytic mechanisms. To determine the effects of d-lactic acid on bovine neutrophil functions, we pretreated cells with different concentrations of D-lactic acid and measured intracellular pH using 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM) and calcium flux using FLUO-3 AM-loaded neutrophils. Reactive oxygen species (ROS) production was measured using a luminol chemiluminescence assay, and MMP-9/gelatinase-B granule release was measured by zymography. CD11b and CD62L/l-selectin expression, changes in cell shape, superoxide anion production, phagocytosis of Escherichia coli-Texas red bioparticles, and apoptosis were all measured using flow cytometry. Our results demonstrated that D-lactic acid reduced ROS production, CD11b upregulation and MMP-9 release in bovine neutrophils treated with 100 nM platelet-activating factor (PAF). D-lactic acid induced MMP-9 release and, at higher concentrations, upregulated CD11b expression, decrease L-selectin expression, and induces late apoptosis. We concluded that D-lactic acid can interfere with neutrophil functions induced by PAF, leading to reduced innate immune responses during bacterial infections. Moreover, the increase of MMP-9 release and CD11b expression induced by 10mM D-lactic acid could promote an nonspecific neutrophil-dependent inflammatory reaction in cattle with acute ruminal acidosis.

Kinetics of inhibition of purified bovine neutrophil matrix metalloproteinase 9 by low-molecular-weight inhibitors

OBJECTIVE

To measure the effects of lowmolecular-weight inhibitors on the activity of bovine neutrophil matrix metalloproteinase 9 (MMP-9).

SAMPLE POPULATION

Bovine MMP-9 purified from bovine neutrophilconditioned medium.

PROCEDURES

Neutrophils were degranulated by stimulation with phorbol ester. Enzyme purification was performed by use of gelatin affinity and gel-filtration chromatography. Activated enzyme was incubated with inhibitors prior to addition of substrate (gelatin fluorescein conjugate or fluorogenic peptide). Rates of enzymatic cleavage were determined by monitoring fluorescence as the reactions progressed. Values of IC(50) (molar concentration of compound that inhibits specific activity by 50%) and K(I) (in vitro inhibition constant) were determined.

RESULTS

Rates of enzymatic activity of monomeric and dimeric bovine MMP-9 measured by use of gelatin and peptide substrates were linear with respect to time and concentrations of enzyme and substrate. The MMP-9 was potently inhibited by hydroxamic acids (IC(50) for gelatin, 29.2 to 55.7 nM; IC(50) for peptide, 4.8 to 24.6 nM; K(I), 0.2 to 0.5 nM), whereas tetracyclines (IC(50) for gelatin, 30.1 to 112.7 MM; IC(50) for peptide, 48.0 to 123.8 MM; K(I), 25.2 to 61.4 microM) and chlorhexidine (IC(50) for gelatin, 139.1MM; IC(50) for peptide, 672.5MM to 1.7 mM; K(I), 495.0 to 663.0 MM) had limited inhibition. Gelatinase-specific inhibitor SB-3CT had intermediate potency (IC(50) for peptide, 185.0 to 290.0 nM; K(I), 66.5 to 86.0 nM).

CONCLUSIONS AND CLINICAL RELEVANCE

Bovine MMP-9 was potently inhibited by hydroxamic acids and gelatinase inhibitor. These compounds may be useful as modulators of neutrophil-mediated protease activity in cattle.

In vitro effects of lactoferrin on lipopolysaccharide-induced proliferation, gene expression, and prostanoid production by bovine peripheral blood mononuclear cells

OBJECTIVE

To evaluate the effect of lactoferrin on lipopolysaccharide (LPS)-induced proliferation of bovine peripheral blood mononuclear cells (PBMCs), gene expression of inflammatory mediators, and production of prostanoids in vitro.

SAMPLE POPULATION

PBMCs isolated from 15 Holstein bull calves.

PROCEDURES

Mixed populations of PBMCs were isolated by differential centrifugation. Proliferation assays were conducted in 96-well plates designed to allow addition of lactoferrin (200 ng/mL) with and without LPS (1 microg/mL) in a checkerboard design. Incorporation of 3H-thymidine was used to determine proliferation of PBMCs. Prostaglandin E2 production was determined in culture-conditioned medium by use of enzyme immunoassay. Effects of lactoferrin on LPS-induced gene expression of cyclooxygenase (COX)-2 and matrix metalloproteinase (MMP)-9 were monitored by use of PCR assays.

RESULTS

Lactoferrin supplementation significantly reduced LPS-induced incorporation of 3H-thymidine and production of prostaglandin E2 by PBMCs. Lactoferrin reduced LPS-induced expression of COX-2 and MMP-9 mRNA.

CONCLUSIONS AND CLINICAL RELEVANCE

Lactoferrin reduced LPS-induced cellular proliferation, inflammatory mediator gene expression, and prostaglandin E2 production by bovine PBMCs in vitro. These effects may be beneficial in reducing the impact of endotoxemia in neonates.

Gelatinolytic matrix metalloproteinases-2 and -9 in tracheobronchial lavage fluid obtained from calves with concurrent infections of Pasteurella multocida and Mycoplasma bovirhinis

OBJECTIVE

To study gelatinolytic matrix metalloproteinases (MMPs) in tracheobronchial lavage fluid (TBLF) obtained from clinically normal calves and calves with Pasteurella multocida infection.

SAMPLE POPULATION

Samples of TBLF obtained from 11 calves with clinical signs of respiratory tract disease and growth of P multocida and Mycoplasma spp during culture of TBLF and samples of TBLF from 6 clinically normal calves with no bacterial growth during culture of TBLF.

PROCEDURE

MMPs in TBLF were analyzed by use of gelatin zymography. Gelatinases were identified on the basis of molecular weights and inhibition by EDTA.

RESULTS

The main gelatinolytic MMPs detected were the proform (90 to 110 kd) and active form (75 to 85 kd) of MMP-9 (gelatinase B) and the proform (67 to 75 kd) and active form (< 65 kd) of MMP-2 (gelatinase A). Increased amounts of active MMP-2 and MMP-9 were detected in TBLF of calves with respiratory tract disease, compared with amounts of active MMP-2 and MMP-9 in TBLF of clinically normal calves. Concurrent infection with Mycoplasma bovirhinis in calves with pneumonia attributable to P multocida was associated with higher concentrations of MMP-9.

CONCLUSIONS AND CLINICAL RELEVANCE

The host response to P multocida includes increases in MMP-2 and MMP-9 concentrations in TBLF. Greater amounts of MMPs detected in calves with concurrent M bovirhinis and P multocida infection indicates synergism between these organisms.

Excessive matrix metalloproteinase-9 in the plasma of community-acquired pneumonia

BACKGROUND

It has been shown that matrix metalloproteinase-9 (MMP-9) is involved in the pathogenesis of various pulmonary inflammatory diseases. We determined the MMP-9 concentration in the plasma of community-acquired pneumonia (CAP) patients before and after antibiotic treatment.

METHODS

Gelatin zymography and ELISA analysis were used to measure MMP-9 activity and MMP-9 level, respectively, in 35 control subjects and 46 CAP patients.

RESULTS

WBC counts, neutrophils, MMP-9 activity and MMP-9 level were significantly higher in CAP patients compared with that of control subjects (P<0.001), while MMP-9 activity and MMP-9 level were returned to normal after the antibiotic treatment (P<0.001). In addition, MMP-9 level correlated positively with WBC counts and neutrophils number both before and after the antibiotic treatment.

CONCLUSIONS

MMP-9 may play an important role in the pathogenesis of CAP with a positive correlation with the number of neutrophils.