Effectiveness of nurse-led services for people with chronic disease in achieving an outcome of continuity of care at the primary-secondary healthcare interface: A quantitative systematic review.

BACKGROUND: Globally, chronic disease is a leading cause of illness, disability and death and an important driver of health system utilization and spending. Continuity of care is a significant component of quality healthcare. However, an association between nurse-led services, interventions, patient outcomes and continuity of care at the primary and secondary interface as an outcome, has not been established for people with chronic disease. OBJECTIVE: To identify the effectiveness of nurse-led services for people with chronic disease in achieving an outcome of continuity of care at the primary-secondary healthcare interface. DESIGN: Quantitative systematic review. DATA SOURCES: Systematic searches of Medline, Cochrane, Embase, Emcare, JBI and Scopus databases were conducted of studies published between 1946 and May 2019 using the search terms "nurse", "continuity of care" and "chronic disease". REVIEW METHODS: Quality of the included studies was assessed using the Cochrane risk of bias tool for randomized controlled trials and Joanna Briggs Institute quality appraisal checklists. A second reviewer screened 10% of full text articles and all articles in critical appraisal. Studies were excluded from the review if they were of poor methodological quality or the description of the effect of the nurse-led service was inadequately reported. RESULTS: Fourteen studies were included in the review (n=4,090 participants). All studies incorporated recognized continuity of care interventions. The nurse-led services were associated with fewer hospitalizations, reduced by 2-8.9% and re-admissions reduced by 14.8-51% (n=886). Reporting of positive patient experiences and improvement in symptoms and lifestyle was also evident. An association of nurse-led services with improved continuity of care between primary and secondary health services as an outcome per se could not be concluded. CONCLUSION: Nurse-led services for adults provide coordinated interventions that support continuity of care for people with chronic disease in both the primary and secondary healthcare settings that are associated with reduced hospitalizations or readmissions and patient satisfaction. However, the limited use of validated continuity of care outcome measurement tools precluded establishing correlations between interventions, patient outcomes and continuity of care as a specific outcome.

Prevalence and changes in analgesic medication utilisation 1 year prior to total joint replacement in an older cohort of patients.

OBJECTIVES: To evaluate the prevalence and change in analgesic medications use prior to joint replacement in older patients between 2001 and 2012. METHODS: A population based epidemiological study was conducted. Opioids, non-steroidal anti-inflammatories (NSAIDs), paracetamol, corticosteroid injections, medications for neuropathic pain, hypnotics, and muscle relaxants supplied 1 year prior to total knee replacement (TKR, n = 15,517) and hip replacement (THR, n = 10,018) were assessed. Patient characteristics and surgical indication adjusted prevalence ratios (PRs) and 95% confidence intervals (CI) are provided. RESULTS: From 2001 to 2012, in the TKR cohort (median age 78.9) the prevalence of opioid use prior to surgery increased from 37% to 49% (PR = 1.01, 95% CI 1.00-1.01, P = 0.01), while in the THR cohort (median age 81.1) it increased from 44% to 54% (PR = 1.01, 95% CI 1.01-1.02, P < 0.001). Paracetamol use increased from 52% to 61% (PR = 1.0, 95% CI 1.0-1.0, P = 0.913) in the TKR cohort and from 55% to 67% (PR = 1.01, 95% CI 1.00-1.01, P = 0.005) in the THR cohort. Neuropathic pain medication use increased from 5% to 11% in the TKR cohort (PR = 1.04, 95% CI 1.02-1.06, P < 0.0001) and from 6% to 12% in the THR cohort (PR = 1.06, 95% CI 1.04-1.09, P < 0.0001). NSAID use decreased from 76% to 50% in the TKR cohort (PR = 0.96, 95% CI 0.95-0.96, P < 0.0001), and from 81% to 47% in THR cohort (PR = 0.95, 95% CI 0.94-0.95, P < 0.0001). Corticosteroid injections prevalence also decreased (TKR: 21-18%, PR = 0.97, 95% CI 0.96-0.97, P < 0.001, THR: 18-17%, PR = 0.97, 95% CI 0.96-0.98, P < 0.001). CONCLUSION: Pain medication utilization prior to joint replacement surgery changed significantly in this national older cohort of patients during the 2000s.

HLA Mismatching Favoring Host-Versus-Graft NK Cell Activity Via KIR3DL1 Is Associated With Improved Outcomes Following Lung Transplantation.

Chronic lung allograft dysfunction (CLAD) is linked to rejection and limits survival following lung transplantation. HLA-Bw4 recipients of HLA-Bw6 grafts have enhanced host-versus-graft (HVG) natural killer (NK) cell activity mediated by killer cell immunoglobulin-like receptor (KIR)3DL1 ligand. Because NK cells may promote tolerance by depleting antigen-presenting cells, we hypothesized improved outcomes for HLA-Bw4 recipients of HLA-Bw6 grafts. We evaluated differences in acute cellular rejection and CLAD-free survival across 252 KIR3DL1+ recipients from University of California, San Francisco (UCSF). For validation, we assessed survival and freedom from bronchiolitis obliterans syndrome (BOS), retransplantation, or death in 12 845 non-KIR typed recipients from the United Network for Organ Sharing (UNOS) registry. Cox proportional hazards models were adjusted for age, gender, ethnicity, transplant type, and HLA mismatching. HVG-capable subjects in the UCSF cohort had a decreased risk of CLAD or death (hazard ratio [HR] 0.57, 95% confidence interval [CI] 0.36-0.88) and decreased early lymphocytic bronchitis. The HVG effect was not significant in subjects with genotypes predicting low KIR3DL1 expression. In the UNOS cohort, HVG-capable subjects had a decreased risk of BOS, retransplant, or death (HR 0.95, 95% CI 0.91-0.99). Survival improved with the higher-affinity Bw4-80I ligand and in Bw4 homozygotes. Improved outcomes in HVG-capable recipients are consistent with a protective NK cell role. Augmentation of NK activity could supplement current immunosuppression techniques.

Medication use and potentially high-risk prescribing in older patients hospitalized for diabetes: a missed opportunity to improve care?

AIMS: To examine the appropriateness of medicine use and potentially high-risk prescribing before and after hospitalization for diabetes. METHODS: A retrospective cohort study of patients hospitalized for diabetes was conducted using administrative data from the Australian Government Department of Veterans' Affairs for the period between 1 January 2012 and 31 December 2012. The appropriateness of medicine use and potentially high-risk prescribing, including hyper-polypharmacy and associated treatment conflicts, were examined for the 120-day periods before and after hospitalization. RESULTS: A total of 876 patients were hospitalized for a diabetes-related complication. Of these, 25% were not dispensed an antidiabetic medicine 4 months before hospitalization and 25% had not had their HbA1c levels measured in the preceding 6 months. The use of antidiabetic medicines increased to 85% after hospitalization, with a 25.6% relative increase (95% CI 10.9-42.1) in the proportion of those dispensed insulin. The prevalence of high-risk prescribing before hospital admission was high; 70% had > 10 medicines dispensed, a third had at least one treatment conflict and half were dispensed a potentially inappropriate medicine. The use of long-acting sulphonylureas and corticosteroids had relative decreases of 46.0% (95% CI 17.0-64.9) and 29.9% (95% CI 8.8-46.0), respectively. Few changes in other high-risk prescribing patterns were observed after discharge. CONCLUSIONS: This study has identified poor medication-related care and, in particular, high-risk-prescribing in people subsequently hospitalized for diabetes. While diabetes medicine use improved after hospitalization, there was little change in potentially inappropriate medicine use, which suggests that an opportunity to improve medication use in this older vulnerable population has been missed.

Effect of a general practitioner management plan on health outcomes and hospitalisations in older patients with diabetes.

BACKGROUND: Little is known about the impact of a general practitioner management plan (GPMP) on health outcomes of patients with diabetes. AIM: To examine the impact of a GPMP on the risk of hospitalisation for diabetes. METHODS: A retrospective study using administrative data from the Australian Government Department of Veterans' Affairs was conducted (1 July 2006 to 30 June 2014) of diabetes patients either exposed or unexposed to a GPMP. The primary end-point was the risk of first hospitalisation for a diabetes-related complication and was assessed using Cox proportional hazard regression models with death as a competing risk. Secondary end-points included rates of receiving guideline care for diabetes, with differences assessed using Poisson regression analyses. RESULTS: A total of 16 214 patients with diabetes were included; 8091 had a GPMP, and 8123 did not. After 1 year, 545 (6.7%) patients with a GPMP and 634 (7.8%) of patients without a GPMP were hospitalised for a diabetes complication. There was a 22% reduction in the risk of being hospitalised for a diabetes complication (adjusted hazard ratio (HR) 0.78, 95% confidence interval (CI) 0.69-0.87, P < 0.0001) for those who received a GPMP by comparison to those who did not. Increased rates of diabetes guideline care, HbA1c claims (adjusted HR 1.29, 95% CI 1.25-1.33) and microalbuminura claims (adjusted HR 1.65, 95% CI 1.58-1.72) were observed after a GPMP. CONCLUSION: Provision of a GPMP in older patients with diabetes resulted in improved health outcomes, delaying the risk of hospitalisation at 12 months for diabetes complications. GPMP should be included as part of routine primary care for older patients with diabetes.

Modelling Medications for Public Health Research.

Most patients with chronic disease are prescribed multiple medications, which are recorded in their personal health records. This is rich information for clinical public health researchers but also a challenge to analyse. This paper describes the method that was undertaken within the Public Health Research Data Management System (PHReDMS) to map medication data retrieved from individual patient health records for population health researcher's use. The PHReDMS manages clinical, health service, community and survey research data within a secure web environment that allows for data sharing amongst researchers. The PHReDMS is currently used by researchers to answer a broad range of questions, including monitoring of prescription patterns in different population groups and geographic areas with high incidence/prevalence of chronic renal, cardiovascular, metabolic and mental health issues. In this paper, we present the general notion of abstraction network, a higher level network that sits above a terminology and offers compact and more easily understandable view of its content. We demonstrate the utilisation of abstraction network methodology to examine medication data from electronic medical records to allow a compact and more easily understandable view of its content.

Hospitalization for drug-induced hepatotoxicity: linking Y-codes with pharmaceutical claims data to identify implicated medicines.

WHAT IS KNOWN AND OBJECTIVE: Hospital admissions associated with an adverse drug reaction are often coded to the International Classification of Diseases external cause Y-codes, denoting the medicine class deemed to cause the adverse drug reaction. Matching hospital data with outpatient dispensing data has the potential to identify the specific causative medicines but the ability to identify the causative medicines in this way has not been previously assessed. This study aimed to determine the proportion of Y-coded hospitalizations for drug-induced hepatotoxicity that could be matched with a potential causative medicine from outpatient dispensing data. METHODS: A retrospective cohort study was undertaken from 1 Jan 2005 to 30 June 2012 using data from the Australian Government Department of Veterans' Affairs of all admissions coded to drug-induced hepatotoxicity. Medicine use in the 6 months prior to hospitalization was examined to identify the probable causative medicines. RESULTS AND DISCUSSION: Thirty five admissions were identified for 31 patients. All admissions were preceded by use of medicines known to cause hepatotoxicity. Twenty four admissions had a Y-code recorded, of which 19 admissions had at least one Y-code specifying the causative medicine class (22 Y-codes). Of the 22 Y-codes, 95% could be successfully matched with a medicine from the same class that had been dispensed in the 6 months prior to admission. Further, 92% were preceded by use of multiple hepatotoxic medicines. WHAT IS NEW AND CONCLUSION: Results of our study demonstrate that hospital administrative data can be linked to prescription dispensing data to identify specific medicines suspected of causing the adverse drug reaction.

Antithrombotic use following transient ischaemic attack or ischaemic stroke among older Australians with atrial fibrillation.

Hospital audits may underestimate anticoagulant use among acute ischaemic stroke patients with atrial fibrillation (AF), as treatment may commence after discharge. To account for this, antithrombotic use in the 4 months after hospitalisation for transient ischaemic attack or ischaemic stroke among AF patients was assessed using claims data. Results suggest that treatment may be commenced soon after discharge and should be considered when assessing prevalence of use.

General practitioner management plans delaying time to next potentially preventable hospitalisation for patients with heart failure.

BACKGROUND: Several studies have shown that the Australian Medicare-funded chronic disease management programme can lead to improvements in care processes. No study has examined the impact on long-term health outcomes. AIMS: This retrospective cohort study assessed the association between provision of a general practitioner management plan and time to next potentially preventable hospitalisation for older patients with heart failure. METHODS: We used the Australian Government Department of Veterans' Affairs (DVA) claims database and compared patients exposed to a general practitioner management plan with those who did not receive the service. Kaplan-Meier analysis and Cox proportional hazards models were used to compare time until next potentially preventable hospitalisation for heart failure between the exposed and unexposed groups. RESULTS: There were 1993 patients exposed to a general practitioner management plan and 3986 unexposed patients. Adjusted results showed a 23% reduction in the rate of potentially preventable hospitalisation for heart failure at any time (adjusted hazard ratio, 0.77; 95% confidence interval, 0.64 to 0.92; P = 0.0051) among those with a general practitioner management plan compared with the unexposed patients. Within one year, 8.6% of the exposed group compared with 10.7% of the unexposed group had a potentially preventable hospitalisation for heart failure. CONCLUSIONS: A general practitioner management plan is associated with delayed time to next potentially preventable hospitalisation for heart failure.

Bronchoalveolar lavage cell immunophenotyping facilitates diagnosis of lung allograft rejection.

Supplementary methods to identify acute rejection and to distinguish rejection from infection may improve clinical outcomes for lung allograft recipients. We hypothesized that distinct bronchoalveolar lavage (BAL) cell profiles are associated with rejection and infection. We retrospectively compared 2939 BAL cell counts and immunophenotypes against concomitantly obtained transbronchial biopsies and microbiologic studies. We randomly assigned 317 subjects to a derivation or validation cohort. BAL samples were classified into four groups: infection, rejection grade ≥A1, both or neither. We employed generalized estimating equation and survival modeling to identify clinical predictors of rejection and infection. We found that CD25(+) and natural killer cell percentages identified a twofold increased odds of rejection compared to either the infection or the neither infection nor rejection groups. Also, monocytes, lymphocytes and eosinophil percentages were independently associated with rejection. A four-predictor scoring system had high negative predictive value (96-98%) for grade ≥A2 rejection, predicted future rejection in the validation cohort and predicted increased risk of bronchiolitis obliterans syndrome in otherwise benign samples. In conclusion, BAL cell immunophenotyping discriminates between infection and acute rejection and predicts future outcomes in lung transplant recipients. Although it cannot replace histopathology, immunophenotyping may be a clinically useful adjunct.

Comorbid chronic diseases, discordant impact on mortality in older people: a 14-year longitudinal population study.

OBJECTIVES: To determine the impact of comorbid chronic diseases on mortality in older people. DESIGN: Prospective cohort study (1992-2006). Associations between numbers of chronic diseases or mutually exclusive comorbid chronic diseases on mortality over 14 years, by Cox proportional hazards model adjusting for sociodemographic variables or Kaplan-Meier analyses, respectively. SETTING: Population based, Australia. PARTICIPANTS: 2087 randomly selected participants aged ≥65 years old, living in the community or institutions. MAIN RESULTS: Participants with 3-4 or ≥5 diseases had a 25% (95% CI 1.05 to 1.5, p=0.01) and 80% (95% CI 1.5 to 2.2, p<0.0001) increased risk of mortality, respectively, by comparison with no chronic disease, after adjusting for age, sex and residential status. When cardiovascular disease (CVD), mental health problem or diabetes were comorbid with arthritis, there was a trend towards increased survival (range 8.2-9.5 years) by comparison with CVD, mental health problem or diabetes alone (survival 5.8-6.9 years). This increase in survival with arthritis as a comorbidity was negated when CVD and mental health problems or CVD and diabetes were present in disease combinations together. CONCLUSION: Older people with ≥3 chronic diseases have increased risk of mortality, but discordant effects on survival depend on specific disease combinations. These results raise the hypothesis that patients who have an increased likelihood of opportunity for care from their physician are more likely to have comorbid diseases detected and managed.

Tissue-selective mast cell reconstitution and differential lung gene expression in mast cell-deficient Kit(W-sh)/Kit(W-sh) sash mice.

BACKGROUND: Mast cell-deficient Kit(W)/Kit(W-v) mice are an important resource for studying mast cell functions in vivo. However, because they are compound heterozygotes in a mixed genetic background and are infertile, they cannot be crossed easily with other mice. OBJECTIVE: To overcome this limitation, we explored the use of Kit(W-sh)/Kit(W-sh) mice for studying mast cell biology in vivo. RESULTS: These mice are in a C57BL/6 background, are fertile and can be bred directly with other genetically modified mice. Ten-week-old Kit(W-sh)/Kit(W-sh) are profoundly mast cell-deficient. No mast cells are detected in any major organ, including the lung. Gene microarrays detect differential expression of just seven of 16,463 genes in lungs of Kit(W-sh)/Kit(W-sh) mice compared with wild-type mice, indicating that resting mast cells regulate expression of a small set of genes in the normal lung. Injecting 10(7) bone marrow-derived mast cells (BMMC) into tail veins of Kit(W-sh)/Kit(W-sh) mice reconstitutes mast cell populations in lung, stomach, liver, inguinal lymph nodes, and spleen, but not in the tongue, trachea or skin. Injection of BMMC into ear dermis or peritoneum reconstitutes mast cells locally in these tissues. When splenectomized Kit(W-sh)/Kit(W-sh) mice are intravenously injected with BMMC, mast cells circulate longer and are found more often in the liver and inguinal lymph nodes, indicating that the spleen acts as a reservoir for mast cells following injection and limits migration to some tissues. CONCLUSION: In summary, these findings show that mast cell-deficient Kit(W-sh)/Kit(W-sh) mice possess unique attributes that favour their use for studying mast cell functions in vivo.

Genetic deficiency of human mast cell alpha-tryptase.

BACKGROUND: Human alpha- and beta-tryptases are proteases secreted by mast cells. Beta (but not alpha) tryptases are implicated in asthma. Genes encoding both types of tryptases cluster on chromosome 16p13.3. OBJECTIVE: This study examines the hypothesis, generated from mapping data, that alpha-alleles compete with some beta-alleles at one locus and that an adjacent locus contains beta-alleles exclusively. This hypothesis predicts that beta-alleles outnumber alpha and that some genomes lack alpha genes altogether. METHODS: To test this hypothesis, we developed PCR-based techniques to distinguish alpha from beta genes. We then genotyped genomic DNA from individuals and tryptase-expressing cell lines. RESULTS: In support of our hypothesis, we find that alpha-tryptase deficiency affects 80/274 (29%) of individuals surveyed. The genotype of the alpha-deficient individuals is betabetabetabeta, due to inheritance of four beta genes. The percentage of the population with the mixed genotypes alphaalphabetabeta and alphabetabetabeta is 21% and 50%, respectively. Accounting for all alpha- and beta-alleles at the tandem loci on 16p13.3, overall alpha-allele frequency is only 0.23, with beta-alleles considerably outnumbering alpha as hypothesized. In samples of defined ethnicity, alpha deficiency affects 45% of Caucasians, but a much lower percentage of other backgrounds, including African-Americans and Asians. Examination of cell lines reveals that HMC-1 and U-937 lack alpha-genes; thus, lack of alpha transcripts in these cells is due to absence of alpha-genes rather than beta-selective transcription. By contrast, alpha-transcribing Mono Mac 6 and KU812 cells contain alpha- and beta-genes. CONCLUSIONS: Genetic alpha-tryptase deficiency is common and varies strikingly between ethnic groups. Because beta-tryptases are implicated in allergic disorders, inherited differences in alpha/beta-genotype may affect disease susceptibility, severity and response to tryptase inhibitor therapy.

Expression and function of proteinase-activated receptor 2 in human bronchial smooth muscle.

Trypsin and mast cell tryptase cleave proteinase-activated receptor 2 (PAR2) to induce alterations in contraction of airway smooth muscle that have been implicated in asthma in experimental animals. Although tryptase inhibitors are under development for treatment of asthma, little is known about the localization and function of PAR2 in human airways. We detected PAR2 expression in primary cultures of human airway smooth muscle cells using reverse transcriptase/polymerase chain reaction (RT-PCR) and immunofluorescence. The PAR2 agonists trypsin, tryptase, and an activating peptide (SLIGKV-NH2) stimulated calcium mobilization in these cells. PAR2 agonists strongly desensitized responses to a second challenge of trypsin and SLIGKV-NH2, but not to thrombin, indicating that they activate a receptor distinct from the thrombin receptors. Immunoreactive PAR2 was detected in smooth muscle, epithelium, glands, and endothelium of human bronchi. Trypsin, SLIGKV-NH2, and tryptase stimulated contraction of isolated human bronchi. Contraction was increased by removal of the epithelium and diminished by indomethacin. Thus, PAR2 is expressed by human bronchial smooth muscle where its activation mobilizes intracellular Ca2+ and induces contraction. These results are consistent with the hypothesis that PAR2 agonists, including tryptase, induce bronchoconstriction of human airway by stimulating smooth muscle contraction. PAR2 antagonists may be useful drugs to prevent bronchoconstriction.

Up-regulation of endothelial cyclooxygenase-2 and prostanoid synthesis by platelets. Role of thromboxane A2.

Platelet-vascular endothelial cell interactions are central to the maintenance of vascular homeostasis. Thromboxane A2 (TXA2) and prostacyclin (prostaglandin (PG)I2) are the major products of cyclooxygenase (COX) metabolism by platelets and the vascular endothelium, respectively. Here we report the effects of platelet-endothelial interactions on human umbilical vein endothelial cells (HUVECs) COX-2 expression and prostanoid synthesis. Co-incubation of platelets with HUVECs resulted in a dose-dependent induction in COX-2 expression. This was accompanied by a relatively small increase in thromboxane B2 synthesis (2 ng) by comparison to the production of 6-keto-PGF1alpha and PGE2, which increased by approximately 14 and 12 ng, respectively. Abrogation of platelet-HUVEC interactions excluded direct cell-cell contact as a required event. Preincubation of HUVECs with SQ29548, a TXA2 receptor antagonist, dose-dependently inhibited platelet-induced COX-2 expression and prostanoid synthesis. Similarly, if platelet TXA2 synthesis was inhibited no induction of COX-2 was observed. Furthermore, a TXA2 analog, carbocyclic TXA2, induced HUVEC COX-2 expression and the synthesis of 6-keto-PGF1alpha and PGE2. This was also associated with an increase in the expression and activity of PGI synthase and PGE synthase but not TX synthase. Platelet co-incubation (or TXA2) also selectively activated the p44/42 mitogen-activated protein kinase pathway to regulate HUVEC COX-2 expression. Thus it seems that platelet-derived TXA2 can act in a paracrine manner to up-regulate endothelial COX-2 expression and PGI2 synthesis. These observations are of particular importance given the recent observations regarding selective COX-2 inhibitors and the suppression of PGI2 synthesis.

Roles of cyclooxygenase (COX)-1 and COX-2 in prostanoid production by human endothelial cells: selective up-regulation of prostacyclin synthesis by COX-2.

The two cyclooxygenase (COX) isoforms, COX-1 and COX-2, both metabolize arachidonic acid to PGH(2), the common substrate for thromboxane A(2) (TXA(2)), prostacyclin (PGI(2)), and PGE(2) synthesis. We characterized the synthesis of these prostanoids in HUVECs in relation to COX-1 and COX-2 activity. Untreated HUVEC expressed only COX-1, whereas addition of IL-1beta caused induction of COX-2. TXA(2) was the predominant COX-1-derived product, and TXA(2) synthesis changed little with up-regulation of COX-2 by IL-1beta (2-fold increase). By contrast, COX-2 up-regulation was associated with large increases in the synthesis of PGI(2) and PGE(2) (54- and 84-fold increases, respectively). Addition of the selective COX-2 inhibitor, NS-398, almost completely abolished PGI(2) and PGE(2) synthesis, but had little effect on TXA(2) synthesis. The up-regulation of COX-2 by IL-1beta was accompanied by specific up-regulation of PGI synthase and PGE synthase, but not TX synthase. An examination of the substrate concentration dependencies showed that the pathway of TXA(2) synthesis was saturated at a 20-fold lower arachidonic acid concentration than that for PGI(2) and PGE(2) synthesis. In conclusion, endothelial prostanoid synthesis appears to be differentially regulated by the induction of COX-2. The apparent PGI(2) and PGE(2) linkage with COX-2 activity may be explained by a temporal increase in total COX activity, together with selective up-regulation of PGI synthase and PGE synthase, and different kinetic characteristics of the terminal synthases. These findings have particular importance with regard to the potential for cardiovascular consequences of COX-2 inhibition.

Eicosanoid production by human monocytes: does COX-2 contribute to a self-limiting inflammatory response?

The eicosanoids, prostaglandin E2 (PGE2) and thromboxane A2 (TXA2), are involved in inflammatory events. TXA2 has potentially pro-inflammatory actions and PGE2 has actions which can be considered both pro- and antiinflammatory. Therefore, it is potentially significant that production of TXA2 and PGE2 by stimulated monocytes have very different time courses. TXA2 synthesis is immediate and dependent on cyclooxygenase Type 1 (COX-1) activity whereas PGE2 synthesis is delayed and dependent on COX-2 activity. These apparent COX-isotype dependencies of TXA2 and PGE2 synthesis can be explained by differences in the affinities of TXA synthase and PGE synthase for the common substrate, PGH2. The findings have implications for the use of NSAIDs and selective COX-2 inhibitors whose actions can increase the monocyte TXA2/PGE2 ratio.

Dipeptidyl peptidase I is essential for activation of mast cell chymases, but not tryptases, in mice.

Dipeptidyl peptidase I (DPPI) is the sole activator in vivo of several granule-associated serine proteases of cytotoxic lymphocytes. In vitro, DPPI also activates mast cell chymases and tryptases. To determine whether DPPI is essential for their activation in vivo, we used enzyme histochemical and immunohistochemical approaches and solution-based activity assays to study these enzymes in tissues and bone marrow-derived mast cells (BMMCs) from DPPI +/+ and DPPI -/- mice. We find that DPPI -/- mast cells contain normal amounts of immunoreactive chymases but no chymase activity, indicating that DPPI is essential for chymase activation and suggesting that DPPI -/- mice are functional chymase knockouts. The absence of DPPI and chymase activity does not affect the growth, granularity, or staining characteristics of BMMCs and, despite prior predictions, does not alter IgE-mediated exocytosis of histamine. In contrast, the level of active tryptase (mMCP-6) in DPPI -/- BMMCs is 25% that of DPPI +/- BMMCs. These findings indicate that DPPI is not essential for mMCP-6 activation but does influence the total amount of active mMCP-6 in mast cells and therefore may be an important, but not exclusive mechanism for tryptase activation.

Mast cell tissue inhibitor of metalloproteinase-1 is cleaved and inactivated extracellularly by alpha-chymase.

We previously reported that mast cell alpha-chymase cleaves and activates progelatinase B (progel B). Outside of cells, progel B is complexed with tissue inhibitor of metalloproteinase (TIMP)-1, which hinders zymogen activation and inhibits activity of mature forms. The current work demonstrates that dog BR mastocytoma cells, HMC-1 cells, and murine bone marrow-derived mast cells secrete TIMP-1 whose electrophoretic profile in supernatants suggests degranulation-dependent proteolysis. Alpha-chymase cleaves uncomplexed TIMP-1, reducing its ability to inhibit gel B, whereas tryptase has no effect. Sequencing of TIMP-1's alpha-chymase-mediated cleavage products reveals hydrolysis at Phe(12)-Cys(13) and Phe(23)-Val(24) in loop 1 and Phe(101)-Val(102) and Trp(105)-Asn(106) in loop 3 of the NH(2)-terminal domain. TIMP-1 in a ternary complex with progel B and neutrophil gelatinase-associated lipocalin is also susceptible to alpha-chymase cleavage, yielding products like those resulting from processing of free TIMP-1. Thus, alpha-chymase cleaves free and gel B-bound TIMP-1. Incubation of the progel B-TIMP-1-neutrophil gelatinase-associated lipocalin complex with alpha-chymase increases gel B activity 2- to 5-fold, suggesting that alpha-chymase activates progel B whether it exists as free monomer or as a complex with TIMP-1. Furthermore, inhibition of alpha-chymase blocks degranulation-induced TIMP-1 processing (absent in alpha-chymase-deficient HMC-1 cells). Purified alpha-chymase processes TIMP-1 in BR supernatants, generating products like those induced by degranulation. In summary, these results suggest that controlled exocytosis of mast cell alpha-chymase activates progel B even in the presence of TIMP-1. This is the first identification of a protease that overcomes inhibition by bound TIMP-1 to activate progel B without involvement of other proteases.