ß-Glucuronidase, a Regulator of Lyme Arthritis Severity, Modulates Lysosomal Trafficking and MMP-9 Secretion in Response to Inflammatory Stimuli.

The lysosomal enzyme ß-glucuronidase (Gusb) is a key regulator of Lyme-associated and K/B×N-induced arthritis severity. The luminal enzymes present in lysosomes provide essential catabolic functions for the homeostatic degradation of a variety of macromolecules. In addition to this essential catabolic function, lysosomes play important roles in the inflammatory response following infection. Secretory lysosomes and related vesicles can participate in the inflammatory response through fusion with the plasma membrane and release of bioactive contents into the extracellular milieu. In this study, we show that GUSB hypomorphism potentiates lysosomal exocytosis following inflammatory stimulation. This leads to elevated secretion of lysosomal contents, including glycosaminoglycans, lysosomal hydrolases, and matrix metalloproteinase 9, a known modulator of Lyme arthritis severity. This mechanistic insight led us to test the efficacy of rapamycin, a drug known to suppress lysosomal exocytosis. Both Lyme and K/B×N-associated arthritis were suppressed by this treatment concurrent with reduced lysosomal release.

Borrelia burgdorferi arthritis-associated locus Bbaa1 regulates Lyme arthritis and K/B×N serum transfer arthritis through intrinsic control of type I IFN production.

Localized upregulation of type I IFN was previously implicated in development of Borrelia burgdorferi-induced arthritis in C3H mice, and was remarkable due to its absence in the mildly arthritic C57BL/6 (B6) mice. Independently, forward genetics analysis identified a quantitative trait locus on Chr4, termed B. burgdorferi-associated locus 1 (Bbaa1), that regulates Lyme arthritis severity and includes the 15 type I IFN genes. Involvement of Bbaa1 in arthritis development was confirmed in B6 mice congenic for the C3H allele of Bbaa1 (B6.C3-Bbaa1), which developed more severe Lyme arthritis and K/B×N model of rheumatoid arthritis (RA) than did parental B6 mice. Administration of a type I IFN receptor blocking mAb reduced the severity of both Lyme arthritis and RA in B6.C3-Bbaa1 mice, formally linking genetic elements within Bbaa1 to pathological production of type I IFN. Bone marrow-derived macrophages from Bbaa1 congenic mice implicated this locus as a regulator of type I IFN induction and downstream target gene expression. Bbaa1-mediated regulation of IFN-inducible genes was upstream of IFN receptor-dependent amplification; however, the overall magnitude of the response was dependent on autocrine/paracrine responses to IFN-ß. In addition, the Bbaa1 locus modulated the functional phenotype ascribed to bone marrow-derived macrophages: the B6 allele promoted expression of M2 markers, whereas the C3H allele promoted induction of M1 responses. This report identifies a genetic locus physically and functionally linked to type I IFN that contributes to the pathogenesis of both Lyme and RA.

Forward genetic approaches for elucidation of novel regulators of Lyme arthritis severity.

Patients experiencing natural infection with Borrelia burgdorferi display a spectrum of associated symptoms and severity, strongly implicating the impact of genetically determined host factors in the pathogenesis of Lyme disease. Herein, we provide a summary of the host genetic factors that have been demonstrated to influence the severity and chronicity of Lyme arthritis symptoms, and a review of the resources available, current progress, and added value of a forward genetic approach for identification of novel genetic regulators.

Lysosomal ß-glucuronidase regulates Lyme and rheumatoid arthritis severity.

Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most prevalent arthropod-borne illness in the United States and remains a clinical and social challenge. The spectrum of disease severity among infected patients suggests that host genetics contribute to pathogenic outcomes, particularly in patients who develop arthritis. Using a forward genetics approach, we identified the lysosomal enzyme ß-glucuronidase (GUSB), a member of a large family of coregulated lysosomal enzymes, as a key regulator of Lyme-associated arthritis severity. Severely arthritic C3H mice possessed a naturally occurring hypomorphic allele, Gusbh. C57BL/6 mice congenic for the C3H Gusb allele were prone to increased Lyme-associated arthritis severity. Radiation chimera experiments revealed that resident joint cells drive arthritis susceptibility. C3H mice expressing WT Gusb as a transgene were protected from severe Lyme arthritis. Importantly, the Gusbh allele also exacerbated disease in a serum transfer model of rheumatoid arthritis. A known GUSB function is the prevention of lysosomal accumulation of glycosaminoglycans (GAGs). Development of Lyme and rheumatoid arthritis in Gusbh-expressing mice was associated with heightened accumulation of GAGs in joint tissue. We propose that GUSB modulates arthritis pathogenesis by preventing accumulation of proinflammatory GAGs within inflamed joint tissue, a trait that may be shared by other lysosomal exoglycosidases.

Nurse practitioner/physician collaborative practice: an integrative model for professional peer review.

As chief nursing officers partner with physician colleagues to create collaborative models of practice across the care continuum, the role of peer review in achieving quality outcomes cannot be overlooked. This article describes how an integrated healthcare system approached the creation of a unique integrative model for physician/nurse practitioner peer review.

High-throughput genotyping of advanced congenic lines by high resolution melting analysis for identification of Bbaa2, a QTL controlling Lyme arthritis.

Congenic mapping is a powerful strategy to identify genomic loci regulating quantitative traits. Generating congenic lines is an iterative process of refinement that is both time and resource intensive. Here we report an alternative to traditional microsatellite marker analysis or costly high-density oligonucleotide single nucleotide polymorphism (SNP) arrays for congenic genotyping. The identification of inherited SNP variability in congenic lines using high resolution melting analysis (HRMA) represents a novel application of the method. The blocked probe HRMA approach offers a scalable, low cost, closed-tube system that benefits from rapid turnaround times, and unequivocal interpretation. The markedly higher prevalence of SNPs relative to microsatellites in the genome allows much greater flexibility for the identification of new genotyping landmarks as congenic intervals are refined. We have adopted this approach in our development of B6.C3-Bbaa2 congenic lines for the identification of loci regulating murine Lyme arthritis severity. As a result, we have been able to fully genotype individuals prior to weaning age, and expand our number of breeding cages without increasing our colony budget. Thus far, 26 SNP markers have been successfully mapped to the Bbaa2 locus. This has facilitated the identification of 20 novel B6.C3-Bbaa2 congenic lines spanning the original interval.

The effect of etomidate on intracranial pressure and systemic blood pressure in pediatric patients with severe traumatic brain injury.

OBJECTIVE: To evaluate the effects of single-dose etomidate in pediatric patients with intracranial hypertension after severe traumatic brain injury. METHODS: Patients admitted to the pediatric intensive care unit with severe traumatic brain injury were enrolled with the informed consent of their guardians. The experimental intervention was a single dose of etomidate 0.3 mg/kg intravenously. This dosage was administered only when enrolled patients had acute elevations of intracranial pressure (ICP) to over 20 mm Hg for over 5 minutes. ICP and mean arterial pressure (MAP) were monitored continuously. ICP and MAP values for 6 consecutive 5-minute intervals after etomidate administration were averaged for all patients and compared with baseline. RESULTS: Eight patients were enrolled. Mean ICP after etomidate administration was significantly lower than baseline ICP for each 5-minute interval (P < 0.05). The mean MAP for all patients increased from baseline during the first 5-minute interval, but this change was not statistically significant. No patient's MAP decreased below baseline at any time point. CONCLUSIONS: In pediatric patients with severe traumatic brain injury, single-dose etomidate administration resulted in statistically significant reductions in ICP and improvement in cerebral perfusion pressure without significantly altering MAP.