Biomedical subjects

Stacey L Mueller-Ortiz

Publications and source records attributed to Stacey L Mueller-Ortiz.

4 recordsLinked to original sources

PubMed2006

Ablation of the complement C3a anaphylatoxin receptor causes enhanced killing of Pseudomonas aeruginosa in a mouse model of pneumonia.

The C3a anaphylatoxin is a 77-amino acid peptide that is generated by enzymatic cleavage of C3 during activation of the complement system. C3a mediates numerous biological functions on binding its receptor (C3aR), which is present on both myeloid and nonmyeloid cells. To investigate the biological impact of C3a-mediated effects during acute pneumonia caused by Pseudomonas aeruginosa, we subjected C3aR-deficient mice and matched wild-type (WT) mice to P. aeruginosa pulmonary infection. C3aR-deficient mice exhibited increased killing of P. aeruginosa in the lungs, less dissemination of bacteria into the bloodstream, and a decreased inflammatory response to P. aeruginosa pulmonary infection compared with WT mice. To examine whether the absence of C3aR would impact the humoral immune response to P. aeruginosa, we immunized WT and C3aR-deficient mice via intraperitoneal injection with live P. aeruginosa. Both groups of mice developed similar levels of antibody specific to P. aeruginosa. Immunized C3aR-deficient and WT mice were subjected to P. aeruginosa pulmonary infection, and C3aR-deficient mice again displayed increased killing of P. aeruginosa in the lungs, less dissemination of bacteria into the bloodstream, and a decreased inflammatory response in the lungs. Collectively, these data demonstrate that independently of antibody production, absence of C3aR causes enhanced killing of P. aeruginosa despite a diminished inflammatory response in a mouse model of pneumonia.

Animals↗

PubMed2004

Carboxypeptidase N: a pleiotropic regulator of inflammation.

Carboxypeptidase N (CPN) is a plasma zinc metalloprotease, which consists of two enzymatically active small subunits (CPN1) and two large subunits (CPN2) that protect the protein from degradation. CPN cleaves carboxy-terminal arginines and lysines from peptides found in the bloodstream such as complement anaphylatoxins, kinins, and creatine kinase MM (CK-MM). By removing only one amino acid, CPN has the ability to change peptide activity and receptor binding. CPN is a member of a larger family of carboxypeptidases, many of which also cleave arginine and lysine. Because of the highly conserved active sites and the possible redundant functions of carboxypeptidases, it has been difficult to elucidate the role of CPN in disease processes. The future use of gene ablation technology may be the most appropriate way to understand the function of CPN in vivo.

Amino Acid Sequence↗

PubMed2004

The alternative activation pathway and complement component C3 are critical for a protective immune response against Pseudomonas aeruginosa in a murine model of pneumonia.

Pseudomonas aeruginosa is a leading cause of hospital-acquired pneumonia, and approximately 80% of patients with cystic fibrosis are infected with this bacterium. To investigate the overall role of complement and the complement activation pathways in the host defense against P. aeruginosa pulmonary infection, we challenged C3-, C4-, and factor B-deficient mice with P. aeruginosa via intranasal inoculation. In these studies, C3(-/-) mice had a higher mortality rate than C3(+/+) mice. Factor B(-/-) mice, but not C4(-/-) mice, infected with P. aeruginosa had a mortality rate similar to that of C3(-/-) mice, indicating that in this model the alternative pathway of complement activation is required for the host defense against Pseudomonas infection. C3(-/-) mice had 6- to 7-fold more bacteria in the lungs and 48-fold more bacteria in the blood than did C3(+/+) mice at 24 h postinfection. In vitro, phagocytic cells from C3(+/+) or C3(-/-) mice exhibited a decreased ability to bind and/or ingest P. aeruginosa in the presence of C3-deficient serum compared to phagocytic cells in the presence of serum with sufficient C3. C3(-/-) mice displayed a significant increase in neutrophils in the lungs and had higher levels of interleukin-1beta (IL-1beta), IL-6, IL-10, KC, and MIP-2 in the lungs at 24 h postinfection than did C3(+/+) mice. Collectively, these results indicate that complement activation by the alternative pathway is critical for the survival of mice infected with P. aeruginosa and that the protection provided by complement is at least in part due to C3-mediated opsonization and phagocytosis of P. aeruginosa.

Animals↗

PubMed2002

Decreased infectivity despite unaltered C3 binding by a DeltahbhA mutant of Mycobacterium tuberculosis.

HbhA of Mycobacterium tuberculosis is a multifunctional binding protein, binding to both sulfated sugars such as heparin and to human complement component C3. HbhA may therefore interact with host molecules and/or host cells during M. tuberculosis infection and play a role in the pathogenesis of this bacterium. The purpose of this study was to use allelic exchange to create an M. tuberculosis strain deficient in expression of HbhA to determine whether this protein's C3-binding activity plays a role in the pathogenesis of M. tuberculosis. An in-frame, 576-bp unmarked deletion in the hbhA gene was created using sacB as a counterselectable marker. Southern blotting and PCR analyses confirmed deletion of hbhA in the DeltahbhA mutant. The DeltahbhA mutant strain grew at a rate similar to that of the parent in broth culture and in J774.A1 murine macrophage-like cells but was deficient in growth compared to the parent strain in the lungs, liver, and spleen of infected mice. In addition, the DeltahbhA mutation did not reduce binding of M. tuberculosis to human C3 or to J774.A1 cells in the presence or absence of serum, suggesting that in the absence of HbhA, other molecules serve as C3-binding molecules on the M. tuberculosis surface. Taken together, these data indicate that HbhA is important in the infectivity of M. tuberculosis, but its ability to bind C3 is not required for mycobacterial adherence to macrophage-like cells. Using the DeltahbhA mutant strain, a second M. tuberculosis C3-binding protein similar in size to HbhA was identified as HupB, but the role of HupB as a C3-binding protein in intact organisms remains to be determined.

Amino Acid Sequence↗