Combined application of biosponges and an antifibrotic agent for the treatment of volumetric muscle loss.

Volumetric muscle loss (VML) causes irrecoverable loss of muscle mass and strength and results in permanent disability. VML injury shows extensive fibrosis, which impedes functional tissue regeneration. Our lab has created a biosponge scaffold composed of extracellular matrix (ECM) proteins (i.e., biosponge) that can enhance muscle regeneration and function following VML. In this work, a potent small molecule inhibitor of alpha v-subunit containing integrins known as IDL-2965 was incorporated into the biosponges for localized suppression of fibrosis post-VML. Our results demonstrate that local delivery of IDL-2965 via the biosponges attenuated the deposition of fibrotic tissue preceded by a downregulation of profibrotic genes in VML-injured muscles. The reduction in fibrotic tissue had no detrimental effects on muscle mass, function, size, or vascularity. Overall, these findings suggest that the codelivery of biosponges and IDL-2965 is a safe and effective strategy for the mitigation of fibrotic tissue deposition in VML-injured muscles.

The utility of H2 receptor antagonists in preventing infusion-related reactions to paclitaxel chemotherapy.

BACKGROUND: Paclitaxel has a risk of infusion-related reactions (IRRs) and despite no prospective evidence, is often given with premedication including a corticosteroid, H1 antagonist, and H2 antagonist (H2RA). Backorders impacted the supply of intravenous H2RAs at our center, and it was removed as routine premedication. The authors compared the incidence of IRR in patients treated without H2RA to patients receiving standard H2RA premedication. METHODS: The authors reviewed outpatients starting paclitaxel at the Ottawa Hospital from December 2019 to October 2021. Two cohorts were created: patients treated without H2RA premedication (intervention), and those receiving standard H2RA (control). Demographics, treatment, and IRR information were collected retrospectively. Primary end point was rate of grade ≥2 IRRs during first two doses of paclitaxel. RESULTS: A total of 182 patients were treated without H2RA premedication, compared to 184 control patients treated during non-backorder periods. Baseline characteristics included: median age, 63 years; 86% female; and primary tumor 52% breast/24% gynecologic/10% gastric/esophageal/8% lung/6% other. There were no significant differences between cohorts in baseline characteristics. There was no difference in the rate of grade ≥2 IRR between cohorts; 12.1% (22 of 182; 95% confidence interval [CI], 7.7%-17.7%) for patients treated without H2RA, and 15.1% (28 of 185; 95% CI, 10.3%-21.1%) for control patients. The rate of grade ≥3 IRRs were also similar, 4.4% in intervention cohort versus 3.8% in control cohort. CONCLUSIONS: The removal of H2RAs from premedication for paclitaxel did not result in an increased incidence of IRRs. The use of H2RAs in preventing IRRs to paclitaxel should be re-evaluated.

The association of neurodevelopmental abnormalities, congenital heart and renal defects in a tuberous sclerosis complex patient cohort.

BACKGROUND: Tuberous sclerosis complex (TSC) is a rare multi-system genetic disorder characterised by the presence of benign tumours throughout multiple organs including the brain, kidneys, heart, liver, eyes, lungs and skin, in addition to neurological and neuropsychiatric complications. Intracardiac tumour (rhabdomyoma), neurodevelopmental disorders (NDDs) and kidney disorders (KD) are common manifestations of TSC and have been linked with TSC1 and TSC2 loss-of-function mutations independently, but the dynamic relationship between these organ manifestations remains unexplored. Therefore, this study aims to characterise the nature of the relationship specifically between these three organs' manifestations in TSC1 and TSC2 mutation patients. METHODS: Clinical data gathered from TSC patients across South Wales registered with Cardiff and Vale University Health Board (CAV UHB) between 1990 and 2020 were analysed retrospectively to evaluate abnormalities in the heart, brain and kidney development. TSC-related abnormalities such as tumour prevalence, location and size were analysed for each organ in addition to neuropsychiatric involvement and were compared between TSC1 and TSC2 mutant genotypes. Lastly, statistical co-occurrence between organ manifestations co-morbidity was quantified, and trajectories of disease progression throughout organs were modelled. RESULTS: This study found a significantly greater mutational frequency at the TSC2 locus in the cohort in comparison to TSC1. An equal proportion of male and female patients were observed in this group and by meta-analysis of previous studies. No significant difference in characterisation of heart involvement was observed between TSC1 and TSC2 patients. Brain involvement was seen with increased severity in TSC2 patients, characterised by a greater prevalence of cortical tubers and communication disorders. Renal pathology was further enhanced in TSC2 patients, marked by increased bilateral angiomyolipoma prevalence. Furthermore, co-occurrence of NDDs and KDs was the most positively correlated out of investigated manifestations, regardless of genotype. Analysis of disease trajectories revealed a more diverse clinical outcome for TSC2 patients: however, a chronological association of rhabdomyoma, NDD and KD was most frequently observed for TSC1 patients. CONCLUSIONS: This study marks the first empirical investigation of the co-morbidity between congenital heart defects (CHD), NDDs, and KDs in TSC1 and TSC2 patients. This remains a unique first step towards the characterisation of the dynamic role between genetics, heart function, brain function and kidney function during the early development in the context of TSC.

Progesterone receptor modulates ERα action in breast cancer.

Progesterone receptor (PR) expression is used as a biomarker of oestrogen receptor-α (ERα) function and breast cancer prognosis. Here we show that PR is not merely an ERα-induced gene target, but is also an ERα-associated protein that modulates its behaviour. In the presence of agonist ligands, PR associates with ERα to direct ERα chromatin binding events within breast cancer cells, resulting in a unique gene expression programme that is associated with good clinical outcome. Progesterone inhibited oestrogen-mediated growth of ERα(+) cell line xenografts and primary ERα(+) breast tumour explants, and had increased anti-proliferative effects when coupled with an ERα antagonist. Copy number loss of PGR, the gene coding for PR, is a common feature in ERα(+) breast cancers, explaining lower PR levels in a subset of cases. Our findings indicate that PR functions as a molecular rheostat to control ERα chromatin binding and transcriptional activity, which has important implications for prognosis and therapeutic interventions.

The association between pre-conception intuitive eating and gestational weight gain.

PURPOSE: To determine if pre-conception intuitive eating, an adaptive eating behavior, was related to gestational weight gain (GWG) and the likelihood of exceeding GWG recommendations. METHODS: This prospective survey study took place in an outpatient obstetric clinic. Participants completed the pre-conception Intuitive Eating Scale for Pregnancy during a prenatal check-up appointment and total GWG was collected from the medical record. The pre-conception Intuitive Eating Scale for Pregnancy assesses unconditional permission to eat, eating for physical rather than emotional reasons, and reliance on hunger and satiety to inform what, when, and how much to eat. Hierarchical linear multiple regression and logistic multiple regression analyses determined associations between pre-conception intuitive eating and GWG on the total sample and stratified by weight status (normal/underweight, overweight, and obese). RESULTS: The majority of the sample (n = 253) was white, married, employed, had annual household income > $50,000, and had a college degree. No aspects of pre-conception intuitive eating predicted the likelihood of excess GWG. However, in the total sample, unconditional permission to eat (subscale) was inversely related to total GWG (B = -0.16, p < 0.05). Among women with obesity (n = 36), eating for physical rather than emotional reasons (subscale) was inversely related to total GWG (B = -0.47, p < 0.05). DISCUSSION: Some aspects of intuitive eating during the pre-conception period were related to total GWG, particularly for women with obesity. However, intuitive eating scores did not increase or decrease the likelihood of excess GWG. More research is needed to understand the mechanisms for this association before clinical recommendations can be made. LEVEL OF EVIDENCE: Level III (Evidence obtained from well-designed cohort or case-control analytic studies).

Using the Drug Burden Index to identify older adults at highest risk for medication-related falls.

BACKGROUND: The Drug Burden Index (DBI) was developed to assess patient exposure to medications associated with an increased risk of falling. The objective of this study was to examine the association between the DBI and medication-related fall risk. METHODS: The study used a retrospective cohort design, with a 1-year observation period. Participants (n = 1562) were identified from 31 community pharmacies. We examined the association between DBI scores and four outcomes. Our primary outcome, which was limited to participants who received a medication review, indexed whether the review resulted in at least one medication-related recommendation (e.g., discontinue medication) being communicated to the participant's health care provider. Secondary outcomes indexed whether participants in the full sample: (1) screened positive for fall risk, (2) reported 1+ falls in the past year, and (3) reported 1+ injurious falls in the past year. All outcome variables were dichotomous (yes/no). RESULTS: Among those who received a medication review (n = 387), the percentage of patients receiving at least one medication-related recommendation ranged from 10.2% among those with DBI scores of 0 compared to 60.2% among those with DBI scores ≥1.0 (Chi-square (4)=42.4, p < 0.0001). Among those screened for fall risk (n = 1058), DBI scores were higher among those who screened positive compared to those who did not (Means = 0.98 (SD = 1.00) versus 0.59 (SD = 0.74), respectively, p < 0.0001). CONCLUSION: Our findings suggest that the DBI is a useful tool that could be used to improve future research and practice by focusing limited resources on those individuals at greatest risk of medication-related falls.

Care coordination and follow-up practices in the community pharmacy setting: A mixed methods study.

OBJECTIVES: This mixed methods study had 2 aims: (1) to describe the frequency of care coordination between pharmacists, prescribers, and care managers and (2) to identify pharmacists' strategies for care coordination and follow-up in a community pharmacy setting. DESIGN: This study used a mixed methods design. SETTING AND PARTICIPANTS: Pharmacists who were responsible for implementing North Carolina community pharmacy enhanced services network (NC CPESN®) activities in their pharmacy during the first or second year of the 3-year program (September 2014-August 2016). OUTCOME MEASURES: A survey was administered to gather data on care coordination in community pharmacies and for follow-up. In-depth interviews were conducted to expand on the findings from the quantitative data. Descriptive statistics were calculated for survey data. Interviews were recorded, transcribed verbatim, and analyzed using thematic analysis. RESULTS: Surveys were received from 101 pharmacies (82.1% response rate). Fourteen pharmacies with missing responses were removed, resulting in 87 pharmacies being included in the analysis. The majority of pharmacies were single, independent pharmacies (46.5%), and approximately one-third of pharmacies had a clinical pharmacist on the staff (31.1%). To communicate with prescribers, pharmacists most frequently used facsimile (fax) (82.1%) or phone (65.5%). A total of 12 pharmacists participated in the semistructured interviews. Pharmacists defined care coordination as interdisciplinary collaboration and communication among the members of the health care team to provide the best possible patient-centered care. All pharmacists agreed that good health care provider (i.e., care manager and prescriber) relationships are crucial to the success of patient care; however, participants mentioned that building these relationships has been or is currently difficult to establish. CONCLUSION: Care coordination among pharmacists, prescribers, and care managers is important for improving patients' medication management and overall outcomes. To our knowledge, this is the first study to quantify care coordination between pharmacists, prescribers, and care managers and to identify strategies to facilitate care coordination. Results from this study have the potential to inform how care coordination and longitudinal follow-up are best implemented within the community pharmacy setting.

Progressive multifocal leukoencephalopathy secondary to hepatitis C virus infection-related T-cell lymphopenia.

Progressive multifocal leukoencephalopathy (PML) is an uncommon neurological condition known to occur in the setting of T-cell immune suppression. We report a case of hepatitis C virus (HCV) infection-related T-cell lymphopenia manifesting as PML. HCV treatment and transient viral suppression resulted in immunological recovery with clinical stabilisation.

Systematic review of the health-related quality of life issues facing adolescents and young adults with cancer.

PURPOSE: For adolescents and young adults (AYAs), the impact of a cancer diagnosis and subsequent treatment is likely to be distinct from other age groups given the unique and complex psychosocial challenges of this developmental phase. In this review of the literature, we report the health-related quality of life (HRQoL) issues experienced by AYAs diagnosed with cancer and undergoing treatment. METHODS: MEDLINE, EMBASE, CINAHL, PsychINFO and the Cochrane Library Databases were searched for publications reporting HRQoL of AYAs. Issues generated from interviews with AYAs or from responses to patient reported outcome measures (PROMs) were extracted. RESULTS: 166 papers were reviewed in full and comprised 72 papers covering 69 primary studies, 49 measurement development or evaluation papers and 45 reviews. Of the 69 studies reviewed, 11 (16%) used interviews to elicit AYAs' descriptions of HRQoL issues. The majority of the PROMs used in the studies represent adaptations of paediatric or adult measures. HRQoL issues were organised into the following categories: physical, cognitive, restricted activities, relationships with others, fertility, emotions, body image and spirituality/outlook on life. CONCLUSION: The HRQoL issues presented within this review are likely to be informative to health care professionals and AYAs. The extensive list of issues suggests that the impact of a cancer diagnosis and treatment during adolescence and young adulthood is widespread and reflects the complexities of this developmental phase.

Androgen receptor driven transcription in molecular apocrine breast cancer is mediated by FoxA1.

Breast cancer is a heterogeneous disease and several distinct subtypes exist based on differential gene expression patterns. Molecular apocrine tumours were recently identified as an additional subgroup, characterised as oestrogen receptor negative and androgen receptor positive (ER- AR+), but with an expression profile resembling ER+ luminal breast cancer. One possible explanation for the apparent incongruity is that ER gene expression programmes could be recapitulated by AR. Using a cell line model of ER- AR+ molecular apocrine tumours (termed MDA-MB-453 cells), we map global AR binding events and find a binding profile that is similar to ER binding in breast cancer cells. We find that AR binding is a near-perfect subset of FoxA1 binding regions, a level of concordance never previously seen with a nuclear receptor. AR functionality is dependent on FoxA1, since silencing of FoxA1 inhibits AR binding, expression of the majority of the molecular apocrine gene signature and growth cell growth. These findings show that AR binds and regulates ER cis-regulatory elements in molecular apocrine tumours, resulting in a transcriptional programme reminiscent of ER-mediated transcription in luminal breast cancers.

High resolution coherent three dimensional spectroscopy of NO2.

Expansion from coherent 2D spectroscopy to coherent 3D spectroscopy can provide significant advantages when studying molecules that have heavily perturbed energy levels. This paper illustrates such advantages by demonstrating how high resolution coherent 3D (HRC3D) spectroscopy can be used to study a portion of the visible spectrum of nitrogen dioxide. High resolution coherent 2D spectra usually contain rotational and vibrational patterns that are easy to analyze, but severe congestion and complexity preclude its effective use for many parts of the NO2 spectrum. HRC3D spectroscopy appears to be much more effective; multidimensional rotational and vibrational patterns produced by this new technique are easy to identify even in the presence of strong perturbations. A method for assigning peaks, which is based upon analyzing the resulting multidimensional patterns, has been developed. The higher level of multidimensionality is useful for reducing uncertainty in peak assignments, improving spectral resolution, providing simultaneous information on multiple levels and states, and predicting, verifying, and categorizing peaks.

Quality improvement exercises in Inflammatory Bowel Disease (IBD) services: A scoping review.

OBJECTIVE: Quality Improvement initiatives aim to improve care in Inflammatory Bowel Disease (IBD). These address a range of aspects of care including adherence to published guidelines. The objectives of this review were to document the scope and quality of published quality improvement initiatives in IBD, highlight successful interventions and the outcomes achieved. DESIGN/METHOD: We searched MEDLINE, EMBASE, CINAHL and Web of Science. Two reviewers independently screened and extracted data. We included peer reviewed articles or conference proceedings reporting initiatives intended to improve the quality of IBD care, with both baseline and prospectively collected follow-up data. Initiatives were categorised based on problems, interventions and outcomes. We used the Quality Improvement Minimum Quality Criteria Set instrument to appraise articles. We mapped the focus of the articles to the six domains of the IBD standards. RESULTS: 100 studies were identified (35 full text; 65 conference abstracts). Many focused on vaccination, medication, screening, or meeting multiple quality measures. Common interventions included provider education, the development of new service protocols, or enhancements to the electronic medical records. Studies principally focused on areas covered by the IBD standards 'ongoing care' and 'the IBD service', with less focus on standards 'pre-diagnosis', 'newly diagnosed', 'flare management', 'surgery' or 'inpatient care'. CONCLUSION: Good quality evidence exists on approaches to improve the quality of a narrow range of IBD service functions, but there are many topic areas with little or no published quality improvement initiatives. We highlight successful quality improvement interventions and offer recommendations to improve reporting of future studies.

Combined regenerative rehabilitation improves recovery following volumetric muscle loss injury in a rat model.

Volumetric muscle loss (VML) injury causes irreversible deficits in muscle mass and function, often resulting in permanent disability. The current standard of care is physical therapy, but it is limited in mitigating functional deficits. We have previously optimized a rehabilitation technique using electrically stimulated eccentric contraction training (EST) that improved muscle mass, strength, and size in VML-injured rats. A biosponge scaffold composed of extracellular matrix proteins has previously enhanced muscle function postVML. This study aimed to determine whether combining a regenerative therapy (i.e., biosponge) with a novel rehabilitation technique (i.e., EST) could enhance recovery in a rat model of VML. A VML defect was created by removing ~20% of muscle mass from the tibialis anterior muscle in adult male Lewis rats. Experimental groups included VML-injured rats treated with biosponge with EST or biosponge alone (n = 6/group). EST was implemented 2 weeks postinjury at 150 Hz and was continued for 4 weeks. A linear increase in eccentric torque over 4 weeks showed the adaptability of the VML-injured muscle to EST. Combining biosponge with EST improved peak isometric torque by ~52% compared with biosponge treatment alone at 6 weeks postinjury. Application of EST increased MyoD gene expression and the percentage of large (>2000 µm2) type 2B myofibers but reduced fibrotic tissue deposition in VML-injured muscles. Together, these changes may provide the basis for improved torque production. This study demonstrates the potential for combined regenerative and rehabilitative therapy to improve muscle recovery following VML.

Matrix metalloproteinase-10 (MMP-10) interaction with tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2: binding studies and crystal structure.

Matrix metalloproteinase 10 (MMP-10, stromelysin-2) is a secreted metalloproteinase with functions in skeletal development, wound healing, and vascular remodeling; its overexpression is also implicated in lung tumorigenesis and tumor progression. To understand the regulation of MMP-10 by tissue inhibitors of metalloproteinases (TIMPs), we have assessed equilibrium inhibition constants (K(i)) of putative physiological inhibitors TIMP-1 and TIMP-2 for the active catalytic domain of human MMP-10 (MMP-10cd) using multiple kinetic approaches. We find that TIMP-1 inhibits the MMP-10cd with a K(i) of 1.1 × 10(-9) M; this interaction is 10-fold weaker than the inhibition of the similar MMP-3 (stromelysin-1) catalytic domain (MMP-3cd) by TIMP-1. TIMP-2 inhibits the MMP-10cd with a K(i) of 5.8 × 10(-9) M, which is again 10-fold weaker than the inhibition of MMP-3cd by this inhibitor (K(i) = 5.5 × 10(-10) M). We solved the x-ray crystal structure of TIMP-1 bound to the MMP-10cd at 1.9 Å resolution; the structure was solved by molecular replacement and refined with an R-factor of 0.215 (R(free) = 0.266). Comparing our structure of MMP-10cd·TIMP-1 with the previously solved structure of MMP-3cd·TIMP-1 (Protein Data Bank entry 1UEA), we see substantial differences at the binding interface that provide insight into the differential binding of stromelysin family members to TIMP-1. This structural information may ultimately assist in the design of more selective TIMP-based inhibitors tailored for specificity toward individual members of the stromelysin family, with potential therapeutic applications.

COVID-19 booster vaccination in rural community pharmacies.

This study assessed rural community pharmacists' attitudes about COVID-19 vaccine booster doses and explored whether rural pharmacies offered these booster doses. Of the 80 rural Southeastern U.S. pharmacists who completed the online survey, the majority (n = 68, 85 %) offered boosters and 42 (52.5 %) had received the booster themselves. Alabama and Mississippi offered boosters less often than other states, and pharmacists who had foregone receiving COVID-19 vaccination or booster doses were less likely to offer the booster to their patients. Additionally, many pharmacists reported that they and their patients felt the booster was not needed. Community pharmacies provide access points for the COVID-19 booster in rural areas. Interventions for both pharmacists and patients are needed to address hesitancy and improve booster uptake in these communities.

Capturing the True Cost of Breast Cancer Treatment: Molecular Subtype and Stage-Specific per-Case Activity-Based Costing.

BACKGROUND: Breast cancer (BC) treatment is rapidly evolving with new and costly therapeutics. Existing costing models have a limited ability to capture current treatment costs. We used an Activity-Based Costing (ABC) method to determine a per-case cost for BC treatment by stage and molecular subtype. METHODS: ABC was used to proportionally integrate multidisciplinary evidence-based patient and provider treatment options for BC, yielding a per-case cost for the total duration of treatment by stage and molecular subtype. Diagnostic imaging, pathology, surgery, radiation therapy, systemic therapy, inpatient, emergency, home care and palliative care costs were included. RESULTS: BC treatment costs were higher than noted in previous studies and varied widely by molecular subtype. Cost increased exponentially with the stage of disease. The per-case cost for treatment (2023C$) for DCIS was C$ 14,505, and the mean costs for all subtypes were C$ 39,263, C$ 76,446, C$ 97,668 and C$ 370,398 for stage I, II, III and IV BC, respectively. Stage IV costs were as high as C$ 516,415 per case. When weighted by the proportion of molecular subtype in the population, case costs were C$ 31,749, C$ 66,758, C$ 111,368 and C$ 289,598 for stage I, II, III and IV BC, respectively. The magnitude of cost differential was up to 10.9 times for stage IV compared to stage I, 4.4 times for stage III compared to stage I and 35.6 times for stage IV compared to DCIS. CONCLUSION: The cost of BC treatment is rapidly escalating with novel therapies and increasing survival, resulting in an exponential increase in treatment costs for later-stage disease. We provide real-time, case-based costing for BC treatment which will allow for the assessment of health system economic impacts and an accurate understanding of the cost-effectiveness of screening.

Artemether-lumefantrine: an option for malaria.

OBJECTIVE: To review the pharmacology, pharmacokinetics, safety, and efficacy of artemether-lumefantrine for the treatment of Plasmodium falciparum malaria. DATA SOURCES: English-language articles indexed in PubMed (1947-November 2011) were identified, using the search terms artemether-lumefantrine, artemether-lumefantrine AND malaria, Coartem, and Coartem AND malaria. STUDY SELECTION AND DATA EXTRACTION: Available English-language articles were reviewed. In addition, the malaria treatment regimens recommended by region as provided by the World Health Organization and the treatment guidelines from the Centers for Disease Control and Prevention were reviewed. DATA SYNTHESIS: Artemether-lumefantrine is an artemisinin-derived combination antimalarial approved by the Food and Drug Administration in 2009 for the treatment of P. falciparum malaria. The dual mechanisms of action of artemether-lumefantrine provide rapid and sustained parasite clearance. In the reviewed studies, the polymerase chain reaction (PCR)-corrected 28-day cure rates of artemether-lumefantrine were noninferior to the most common comparators, including chloroquine, dapsone, and other artemisinin derivatives (86-100% vs 51-100%, respectively). PCR-corrected day-42 cure rates were 92-99.3% for artemether-lumefantrine versus 62-100% for the comparator groups. The major adverse effects (gastrointestinal and central nervous system) were mild to moderate in severity and did not require a change in therapy. Although adherence to artemether-lumefantrine has been described as a potential problem due to the complicated dosing schedule, studies have described clinical cure rates similar to those of other antimalarials. CONCLUSIONS: Artemether-lumefantrine is a safe and effective treatment for children and adults with P. falciparum malaria.

Role of D-type cyclins in heart development and disease.

A defining feature of embryonic cardiomyocytes is their relatively high rates of proliferation. A gradual reduction in proliferative capacity throughout development culminates in permanent cell cycle exit by the vast majority of cardiomyocytes around the perinatal period. Accordingly, the adult heart has severely limited capacity for regeneration in response to injury or disease. The D-type cyclins (cyclin D1, D2, and D3) along with their catalytically active partners, the cyclin dependent kinases, are positive cell cycle regulators that play important roles in regulating proliferation of cardiomyocytes during normal heart development. While expression of D-type cyclins is generally low in the adult heart, expression levels are augmented in association with cardiac hypertrophy, but are uncoupled from myocyte cell division. Accordingly, re-activation of D-type cyclin expression in the adult heart has been implicated in pathophysiological processes via mechanisms distinct from those that drive proliferation during cardiac development. Growth factors and other exogenous agents regulate D-type cyclin production and activity in embryonic and adult cardiomyocytes. Understanding differences in the precise intracellular mediators downstream from these signalling molecules in embryonic versus adult cardiomyocytes could prove valuable for designing strategies to reactivate the cell cycle in cardiomyocytes in the setting of cardiovascular disease in the adult heart.

The amyloid precursor protein/protease nexin 2 Kunitz inhibitor domain is a highly specific substrate of mesotrypsin.

The amyloid precursor protein (APP) is a ubiquitously expressed transmembrane adhesion protein and the progenitor of amyloid-beta peptides. The major splice isoforms of APP expressed by most tissues contain a Kunitz protease inhibitor domain; secreted APP containing this domain is also known as protease nexin 2 and potently inhibits serine proteases, including trypsin and coagulation factors. The atypical human trypsin isoform mesotrypsin is resistant to inhibition by most protein protease inhibitors and cleaves some inhibitors at a substantially accelerated rate. Here, in a proteomic screen to identify potential physiological substrates of mesotrypsin, we find that APP/protease nexin 2 is selectively cleaved by mesotrypsin within the Kunitz protease inhibitor domain. In studies employing the recombinant Kunitz domain of APP (APPI), we show that mesotrypsin cleaves selectively at the Arg(15)-Ala(16) reactive site bond, with kinetic constants approaching those of other proteases toward highly specific protein substrates. Finally, we show that cleavage of APPI compromises its inhibition of other serine proteases, including cationic trypsin and factor XIa, by 2 orders of magnitude. Because APP/protease nexin 2 and mesotrypsin are coexpressed in a number of tissues, we suggest that processing by mesotrypsin may ablate the protease inhibitory function of APP/protease nexin 2 in vivo and may also modulate other activities of APP/protease nexin 2 that involve the Kunitz domain.