Body mass index and quality of life in people living with HIV

With advances in the treatment of HIV, people living with HIV (PLWH) are now expected to have a near-normal life expectancy, but challenges remain in the form of substantially poorer health-related quality of life (HRQoL) than the general population. Being overweight or obese may pose an additional burden in PLWH, but few studies have evaluated the relationship between body mass index (BMI) and HRQoL in PLWH. This study aimed to evaluate and describe the association between HRQoL and BMI among PLWH in the US. Data were obtained from the 2018 and 2019 US National Health and Wellness Survey, an online, self-reported, general population survey. Analyses included 575 PLWH who self-reported a physician diagnosis and prescription use for the treatment of HIV, as well as 1725 propensity score matched non-HIV controls. After adjusting for age, sex, race, and comorbidities, higher BMI was associated with poorer physical (β =  -0.18, p = 0.005) and general (β =  -0.42, p = 0.014) HRQoL among PLWH. Additionally, PLWH reported poorer mental, physical, and general HRQoL than non-HIV controls; these relationships were not moderated by BMI. The potential negative impact of higher BMI on patients' humanistic outcomes should be considered in HIV management, including selection of treatment.

Quantifying the impact of symptomatic acute hepatic porphyria on well-being via patient-reported outcomes: Results from the Porphyria Worldwide Patient Experience Research (POWER) study

Acute hepatic porphyria (AHP) is a group of rare genetic diseases of heme biosynthesis resulting in severe neurovisceral attacks and chronic complications that negatively impact patients' well-being. This study evaluated the impacts of AHP on patients' physical and emotional health from a global perspective. Adult patients from the United States, Italy, Spain, Australia, Mexico, and Brazil with AHP with >1 porphyria attack within the past 2 years or receiving intravenous hemin and/or glucose for attack prevention completed an online survey assessing demographics, health characteristics, and patient-reported outcomes. Results were analyzed collectively and by patient subgroups. Ninety-two patients with AHP across the six countries completed the survey. More than 70% of patients reported that their physical, emotional, and financial health was fair or poor. Among patients who reported pain, fatigue, and muscle weakness, 94.3%, 95.6%, and 91.4%, respectively, reported that these symptoms limited daily activities. Moderate to severe depression was present in 58.7% of patients, and moderate to severe anxiety in 48.9% of patients. Of the 47% of patients who were employed, 36.8% reported loss in productivity while at work. Among patients, 85.9% reported that they had to change or modify goals that were important to them because of AHP. Aside from differences in healthcare utilization and pain severity, scores did not significantly vary with attack rate or use of hemin or glucose prophylactic treatments. AHP substantially impacts patients' physical and emotional well-being, regardless of hemin or glucose prophylactic treatment or frequency of attacks. This multinational study demonstrates that there is substantial disease burden for patients with AHP, even among those experiencing sporadic attacks or using prophylactic treatment.

The burden of illness of patients with paroxysmal nocturnal haemoglobinuria receiving C5 inhibitors: clinical outcomes and medical encounters from the patient perspective

OBJECTIVES

To assess the clinical and healthcare resource burden among C5 inhibitor (C5i)-treated patients with paroxysmal nocturnal haemoglobinuria (PNH), using patient-reported data.

METHODS

This web-based, cross-sectional survey (01FEB2021-31MAR2021) of adults with PNH treated with eculizumab (France, Germany, UK) or ravulizumab (Germany) included: patient characteristics; treatment patterns/dosage; haematological outcomes (haemoglobin [Hb] levels, transfusions, thrombotic events, breakthrough haemolysis); and medical encounters. Treatment and Hb-level subgroup differences were assessed with statistical significance tests.

RESULTS

Among 71 patients, 98.6% were C5i-treated for ≥3 months. The majority (with reported Hb levels) had levels ≤12.0 g/dL (85.7%; n = 54/63). The mean Hb level was 10.2 g/dL (standard deviation [SD]: 2.0; median 10.0 g/dL). Treatment with above label-recommended doses was reported by 30.4% (eculizumab) and 5.3% (ravulizumab) of patients. Within the past 12 months among patients treated with C5i for ≥1 year: 24.1% had ≥1 transfusion; 3.2% had ≥1 thrombosis; and 28.6% had ≥1 breakthrough haemolysis. Among all patients, 26.8% and 31.0% reported emergency department/room [ER] and inpatient visits, respectively. Mean annual, per-patient all-cause medical encounters were: 0.5 (ER); 1.9 (inpatient); and overall outpatient visits ranged by setting from 2.0 to 6.4. Most encounters were PNH-related, with means of 0.4 (ER); 1.8 (inpatient); and 1.6-5.4 (outpatient). Primary haematological and medical encounter outcomes were similar between treatment as well as Hb-level subgroups, with almost no statistically significant differences.

CONCLUSIONS

Despite at least 3 months of C5i treatment, high proportions of patients with PNH reported low haemoglobin levels and required transfusions and hospitalizations, which suggests remaining unmet needs.

The Burden of Illness of Patients With Paroxysmal Nocturnal Haemoglobinuria Receiving C5 Inhibitors in France, Germany and the United Kingdom: Patient-reported Insights on Symptoms and Quality of Life

OBJECTIVES

To assess the clinical, humanistic, and economic burden of paroxysmal nocturnal haemoglobinuria (PNH) among C5 inhibitor (C5i)-treated patients with PNH METHODS: This was a web-based, cross-sectional survey (01FEB2021-31MAR2021) of adults with PNH treated with eculizumab (France, Germany, UK) or ravulizumab (Germany). Self-reported outcomes included: patient characteristics; patient-reported symptoms; and standardized patient-reported outcomes (e.g., Functional Assessment of Chronic Illness Therapy [FACIT]-Fatigue, European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 [EORTC QLQ-C30]).

RESULTS

Among 71 included patients, 98.6% were C5i-treated for ≥3 months (88.7% ≥12 months); among those with self-reported haemoglobin (Hb) levels (n=63), most (85.7%) were anaemic (defined as ≤12.0 g/dL). Fatigue was the most common symptom at both diagnosis (73.2%) and survey time (63.4%); there were no statistically significant differences in symptom prevalence between treatment subgroups (eculizumab versus ravulizumab). Total FACIT-Fatigue and EORTC QLQ-C30 scores were substantially lower than European general population references, but there were no statistically significant differences between treatment subgroups. Hb level subgroups (<10.5 g/dL versus ≥10.5 g/dL) followed similar trends for all measures, with few significant subgroup differences.

CONCLUSIONS

Results suggest that there remains a considerable burden and unmet need among C5i-treated patients with PNH that requires improved therapies.

The burden of illness in patients with paroxysmal nocturnal hemoglobinuria receiving treatment with the C5-inhibitors eculizumab or ravulizumab: results from a US patient survey

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare and life-threatening disease with symptoms of hemolysis and thrombosis. Current therapies for this complement-mediated disease rely predominantly on inhibition of the C5 complement protein. However, data on treatment responses and quality of life in C5-inhibitor (C5i)-treated PNH patients are scarce. The objective of this study was to determine C5i treatment effects on clinical parameters, PNH symptoms, quality of life, and resource use for PNH patients. This cross-sectional study surveyed 122 individuals in the USA receiving treatment for PNH with C5-targeted monoclonal antibodies, eculizumab (ECU) or ravulizumab (RAV). Despite most patients receiving C5i therapy for ≥ 3 months (ECU 100%, n = 35; RAV 95.4%, n = 83), many patients remained anemic with hemoglobin levels ≤ 12 g/dL in 87.5% (n = 28/32) and 82.9% (n = 68/82) of ECU and RAV recipients, respectively. A majority of patients on ECU (88.6%; n = 31/35) and RAV (74.7%; n = 65/87) reported fatigue symptoms. Among PNH patients receiving C5i therapy for ≥ 12 months, some still reported thrombotic events (ECU, 10.0%, n = 1/10; RAV, 23.5%, n = 4/17) and required transfusions within the past year (ECU, 52.2%, n = 12/23; RAV, 22.6%, n = 7/31). Other patient-reported PNH symptoms included breakthrough hemolysis, shortness of breath, and headaches. Patients reported scores below the average population norms on the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) scales. Overall, this study found that PNH patients receiving ECU or RAV therapy demonstrated a significant burden of illness, highlighting the need for improved PNH therapies.

Preference for Contraceptive Implant Among Women 18-44 years old

Introduction: This study aimed to understand women's preferences regarding the subdermal contraceptive implant and to assess the proportion of women who would be underserved (with increased unintended pregnancies as the consequence) by not providing implant access equal to that of uterine-based long-acting reversible contraceptive methods (LARCs). Methods: A total of 1,200 women aged 18-44 years old (mean: 30.42 ± 7.67 years) participated in a U.S. cross-sectional online survey. To qualify for the study, women had to be sexually active with a male and not pregnant or trying to get pregnant at the time of the study. Women who had undergone a hysterectomy, a bilateral salpingo-oophorectomy, or a tubal ligation, and women with general infertility or those with a vasectomized partner were excluded. Descriptive analyses were conducted and weighted estimates, projecting to the total U.S. population were also provided. Results: The majority of women (72.6%) reported that they would be willing to switch to a LARC, should it be readily available to them. Considering those women who already use an implant and those who would be willing to switch to it, 58% of women would be underserved by not being provided equal access to the subdermal implant. This reduced availability of this type of LARC may alone elevate the number of unintended pregnancies in the United States by ∼8% of all pregnancies per year. Conclusion: Thus, making all the available contraceptive methods and maintaining access to LARCs would help reduce unintended pregnancies and better serve women and their family planning needs.

832. Body Mass Index and Quality of Life in People Living With HIV

Background

Weight gain among people living with HIV (PLWH) on antiretroviral therapy (ART) may lead to obesity. This study evaluated association between body mass index (BMI) and health-related quality of life (HRQoL) from the patient’s perspective.

Methods

A cross-sectional study using self-reported data from the 2018 and 2019 US National Health and Wellness Survey (NHWS), a nationally representative online survey of ~75,000 adults was conducted. Respondents self-reporting a physician diagnosis of and prescription use for treatment of HIV were included. HRQoL was assessed using Short-Form 36-Item Health Survey Version 2 [Mental and Physical Component Summary scores (MCS and PCS)] and EQ-5D-5L [dimension responses: “no” vs “any problems”/“yes”); EQ-Visual Analogue Scale (VAS) score]. Bivariate analyses (chi-square tests for categorical and ANOVA for continuous variables) compared patient characteristics and HRQoL outcomes across BMI (kg/m2) categories: normal weight (NW; 18.5-&lt; 25), overweight (OW; 25-&lt; 30) and obese (OB; ≥30). Multivariable models analyzed each outcome as a function of BMI, controlling for age, sex, race, and Charlson Comorbidity Index (CCI; excluding HIV/AIDS).

Results

A total of 566 respondents were analyzed. Majority were aged ≥50 years (58%) and male (87%). The OB (vs NW) group had higher proportion of respondents who were female (22% vs 10%), Black (37% vs 24%), residing in the South (46% vs 33%), and higher mean CCI score (1.28 vs. 0.97) (Table 1). A higher proportion of OB (vs NW) respondents reported having pain/discomfort and problems with mobility and usual activities but not self-care. Anxiety/depression was reported less in OB vs NW groups (Table 1) However, self-reported use of prescription medications for anxiety (19% vs 20%) and depression (34% vs 25%) was similar in OB and NW groups. PCS and EQ-VAS scores were lower in OB vs OW and NW, but no difference in MCS score was observed (Table 1). Lower PCS and EQ-VAS scores were associated with higher BMI (both p=0.01) but not MCS (p=0.68) in multivariate models.

Conclusion

PLWH with higher BMI have poorer physical and general HRQoL. Impact of potential adverse weight gain and transition to higher BMI on humanistic and clinical outcomes should be considered when selecting ART regimens.

Table 1. Comorbidity Burden and Quality of Life in People Living with HIV by BMI Categories.

Disclosures

Jennifer Ken-Opurum, PhD, Kantar Health (Employee) Girish Prajapati, M.B.B.S., MPH , Merck & Co., Inc. (Employee, Shareholder) Joana E. Matos, PhD, Kantar Health (Employee) Princy N. Kumar, MD, AMGEN (Other Financial or Material Support, Honoraria)Eli Lilly (Grant/Research Support)Gilead (Grant/Research Support, Shareholder, Other Financial or Material Support, Honoraria)GSK (Grant/Research Support, Shareholder, Other Financial or Material Support, Honoraria)Merck & Co., Inc. (Grant/Research Support, Shareholder, Other Financial or Material Support, Honoraria)

Adult Patient Preferences for Long-Acting ADHD Treatments: A Discrete Choice Experiment

BACKGROUND AND OBJECTIVE

Treatment for attention deficit hyperactivity disorder (ADHD) requires a multifaceted approach including psychosocial interventions and pharmacological treatment. This study evaluates preferences for specific attributes associated with different long-acting stimulant treatment among US adults with ADHD.

METHODS

Patients completed an online, cross-sectional survey, incorporating a discrete choice experiment to assess preferences for attributes.

RESULTS

Analyses included 200 adults with ADHD (mean age 33.0 years; 60% self-reporting moderate severity); the mean (SD) Adult ADHD Self-Report Scale-v1.1 score was 45.9 (12.4). Overall, patients valued speed of onset most and risk of rebound least. Three population groups with distinct preferences were identified: side effect-driven (n=69, 35%), quick onset-driven (n=47, 24%) and quick onset and long duration-driven (n=84, 42%).

CONCLUSION

This study shows differences in how adults with ADHD value and assess benefit-risk trade-offs when considering the desired attributes of stimulant treatments, highlighting the importance of patient-physician shared decision-making to optimize the desired benefits of individualized treatment.

Association between red blood cell transfusion dependence and burden in patients with myelodysplastic syndromes: A systematic literature review and meta-analysis

Myelodysplastic syndromes (MDS) are a group of malignant hematologic diseases characterized by ineffective hematopoiesis, which may lead to chronic anemia and transfusion dependency, with up to 30% of patients progressing to acute myeloid leukemia (AML). Studies suggest transfusion dependency may impact overall survival (OS); however, there is a lack of evidence concerning the association between transfusion status (TS) and OS in patients with MDS who become transfusion independent (TI) after treatment. In addition, the holistic impact of TS on other clinical, economic, and humanistic outcomes has not been well understood. We conducted a systematic literature review (SLR) to understand this impact. Ten studies were included and showed consistent decrease in OS in transfusion dependent (TD) compared with TI patients. These findings were confirmed by a meta-analysis (MA) reporting better OS prognosis for TI patients. A second SLR was conducted to understand the association between TS and other clinical, economic, and humanistic outcomes. Twenty-eight studies were included and showed better prognosis for other outcomes, including AML progression and leukemia-free survival for TI patients. Risk of AML progression and cumulative non-leukemic death assessed by the MA showed a trend toward worse prognosis and higher risk of AML progression for TD patients. Lower healthcare resource utilization, better quality of life, and reduced non-leukemic death for TI patients were observed. Studies not eligible for MA also showed better clinical, economic, and humanistic outcomes for TI patients. These findings contribute to understanding the association between transfusion dependence and OS among other outcomes in patients with MDS.

Factors associated with the discontinuation of dipeptidyl peptidase-4 inhibitors (DPP-4is) after initiation of insulin

Objective: Type 2 diabetes (T2D) is a prevalent health problem. Oral agents, with the exception of metformin, are often discontinued with the initiation of insulin. The objective was to understand the proportion of patients discontinuing dipeptidyl peptidase-4 inhibitors (DPP-4is) and the reasons for the decision to discontinue.Methods: A retrospective study using a health claims database investigated discontinuation of DPP-4i in adult patients on a dual therapy of metformin and DPP-4i who initiated insulin (n = 3391). An online survey administered to 406 physicians in the US examined reasons for discontinuation. Physicians surveyed included endocrinologists (34.5%), general practitioners (32.5%), internal medicine specialists (30.5%), and diabetologists (2.5%), treating a monthly average of 154 patients.Results: Among patients treated with metformin and DPP-4is who were newly prescribed insulin, 33.3 and 57.3% discontinued DPP-4i therapy within 3 and 12 months, respectively. Patients who discontinued DPP-4i therapy had higher out-of-pocket costs and a greater proportion of renal and liver disease. Top 3 responses for discontinuation included adverse events/tolerability issues (58.9%), lack of efficacy/treatment goals not being met (55.4%) and additional cost of DPP-4i with insulin (48.5%). Top 3 responses for continuing DPP-4i included meeting treatment goals (70.7%), using a lower dose of insulin (65.3%) and good tolerability (48.0%). Physician characteristics, such as physician specialty, age, gender and location impacted to some extent the reasons for treatment decisions.Conclusions: A large proportion of patients discontinue DPP-4is in the real world when initiating insulin. The impact of physician characteristics in treatment decisions highlights the need for enhanced physician training and support as new clinical data emerges and therapy options are available.

Modulation of P2Y2 receptors in bovine cumulus oocyte complexes: effects on intracellular calcium, zona hardening and developmental competence

The improvement of cryopreserved oocyte survival is imperative for the preservation of female fertility. In this study, we investigate whether P2Y2 receptors (P2Y2R) can be directly implicated in calcium (Ca²⁺) homeostasis misbalances observed during the cryopreservation process of cumulus oocyte complexes (COC). Firstly, RNA was extracted from bovine immature and mature oocytes and cumulus cells and real-time PCR performed to identify P2Y2R transcripts (experiment 1). Changes in intracellular calcium concentration [Ca2+]i of mature COC and oocytes (experiment 2) were measured upon exposure to cryoprotectants (CPA), UTP (P2Y2R stimulator, 100 μM), and/or suramin (P2Y2R inhibitor, 100 and 300 μM). The functional role of P2Y2R was investigated by analyzing the effect on oocyte viability of its modulation prior and during oocyte exposure to CPA (experiment 3). Mature COC were randomly divided into groups, and exposed to CPA and different P2Y2 modulators. Oocytes' viability, cortical granules location, and competence for development were assessed. Results showed that P2Y2R mRNAs are expressed in both oocytes and cumulus cells. Stimulation with UTP and CPA led to [Ca2+]i increase, and this effect was totally or partially blocked by suramin (P2Y2R inhibitor). Oocyte exposure to CPA and UTP reduced embryo rates compared with control and suramin100μM (P ≤ 0.04). The observed enhanced premature zona hardening in oocytes exposed to CPA (P = 0.04) and UTP (P = 0.005) stimulus was inhibited by suramin 100 μM. In conclusion, inhibition of P2Y2R during cryoprotectant exposure reduces premature intracellular Ca²⁺ release and significantly improves the developmental competence of exposed bovine oocytes.

Conjugated linoleic acid improves oocyte cryosurvival through modulation of the cryoprotectants influx rate

BACKGROUND

In cryopreservation, oocytes are subjected to extreme hyperosmotic conditions, inducing large volume changes that, along with an abrupt temperature drop, interfere with their developmental competence. Our objectives in this work were to find conditions enabling an increase in oocyte cryosurvival and subsequent development.

METHODS

Abattoir-derived bovine oocytes were cultured without (Control group) or with trans-10,cis-12 conjugated linoleic acid isomer (CLA group). Comparative observations were made for 1) the oocyte developmental competence after exposure to cryoprotectants followed or not by vitrification/warming, 2) the oocyte membrane permeability to water (using the non-permeant cryoprotectant sucrose) and 3) the oocyte membrane permeability to two cryoprotectants (ethylene glycol, EG, and dimethyl sulfoxide, DMSO). Mature oocytes cultured with or without CLA and vitrified/warmed or only exposed to cryoprotectants without vitrification were subjected to in vitro fertilization; embryo culture proceeded until the blastocyst stage. The oocyte membrane permeabilities to water and cryoprotectants were estimated using mature oocytes subjected to hyperosmotic challenges. For water permeability, 200 mM sucrose was used, whereas for the cryoprotectant permeability, a 10 % solution of both EG and DMSO was used. The data were analyzed using the MIXED procedure and Student's T-test.

RESULTS

CLA supplementation improves the developmental competence of vitrified/warmed and cryoprotectants exposed oocytes (p < 0.01) and reduces their membrane permeability to water (37 %, p < 0.001) and to cryoprotectants (42 %, p < 0.001).

CONCLUSIONS

By slowing the fluxes of water and of permeant cryoprotectants, CLA contributed to improved oocyte cryosurvival and post-thawed viability. This isomer supplementation to the maturation media should be considered when designing new protocols for oocyte cryopreservation.

Zooming into protein oligomerization in neurodegeneration using BiFC

Several neurodegenerative diseases are characterized by the accumulation of misfolded and aggregated proteins, which lead to neurotoxicity. However, the nature of those toxic species is controversial. Developments in optical microscopy and live-cell imaging are essential in providing crucial insight into the molecular mechanisms involved. In particular, the technique of bimolecular fluorescence complementation (BiFC) represents a remarkable improvement for observing protein-protein interactions within living cells. Unlike other techniques, BiFC provides spatial and temporal resolution and can be carried out in a physiological environment. Among other applications, BiFC has been used to study molecular determinants of oligomerization in neurodegenerative disorders, thereby promising to unveil novel targets for therapeutics. We review the applicability of BiFC for investigating the molecular basis of neurodegenerative diseases associated with protein misfolding and aggregation.

Aldosterone increases KCa1.1 (BK) channel-mediated colonic K+ secretion

Mammalian K(+) homeostasis results from highly regulated renal and intestinal absorption and secretion, which balances the unregulated K(+) intake. Aldosterone is known to enhance both renal and colonic K(+) secretion. In mouse distal colon K(+) secretion occurs exclusively via luminal K(Ca)1.1 (BK) channels. Here we investigate if aldosterone stimulates colonic K(+) secretion via BK channels. Luminal Ba(2+) and iberiotoxin (IBTX)-sensitive electrogenic K(+) secretion was measured in Ussing chambers. In vivo aldosterone was augmented via a high K(+) diet. High K(+) diet led to a 2-fold increase of luminal Ba(2+) and IBTX-sensitive short-circuit current in distal mouse colonic mucosa. This effect was absent in BK alpha-subunit-deficient (BK(-/-)) mice. The resting and diet-induced K(+) secretion was stimulated by luminal ionomycin. In BK(-/-) mice luminal ionomycin did not stimulate K(+) secretion. In vitro addition of aldosterone likewise triggered a 2-fold increase in K(+) secretion, which was inhibited by the mineralocorticoid receptor antagonist spironolactone and the BK channel blocker IBTX. Semi-quantification of mRNA from colonic crypts showed up-regulation of BK alpha- and beta(2)-subunits in high K(+) diet mice. The BK channel could be detected luminally in colonic crypt cells by immunohistochemistry. The expression level of the channel in the luminal membrane was strongly up-regulated in K(+)-loaded animals. Taken together, these data strongly suggest that aldosterone-induced K(+) secretion occurs via increased expression of luminal BK channels.

Distal colonic Na(+) absorption inhibited by luminal P2Y(2) receptors

Luminal P2 receptors are ubiquitously expressed in transporting epithelia. In steroid-sensitive epithelia (e.g., lung, distal nephron) epithelial Na(+) channel (ENaC)-mediated Na(+) absorption is inhibited via luminal P2 receptors. In distal mouse colon, we have identified that both, a luminal P2Y(2) and a luminal P2Y(4) receptor, stimulate K(+) secretion. In this study, we investigate the effect of luminal adenosine triphosphate/uridine triphosphate (ATP/UTP) on electrogenic Na(+) absorption in distal colonic mucosa of mice treated on a low Na(+) diet for more than 2 weeks. Transepithelial electrical parameters were recorded in an Ussing chamber. Baseline parameters: transepithelial voltage (V (te)): -13.7 +/- 1.9 mV (lumen negative), transepithelial resistance (R (te)): 24.1 +/- 1.8 Omega cm(2), equivalent short circuit current (I (sc)): -563.9 +/- 63.8 microA/cm(2) (n = 21). Amiloride completely inhibited I (sc) to -0.5 +/- 8.5 microA/cm(2). Luminal ATP induced a slowly on-setting and persistent inhibition of the amiloride-sensitive I (sc) by 160.7 +/- 29.7 microA/cm(2) (n = 12, NMRI mice). Luminal ATP and UTP were almost equipotent with IC(50) values of 10 microM and 3 microM respectively. In P2Y(2) knock-out (KO) mice, the effect of luminal UTP on amiloride-sensitve Na(+) absorption was absent. In contrast, in P2Y(4) KO mice the inhibitory effect of luminal UTP on Na(+) absorption remained present. Semiquantitative polymerase chain reaction did not indicate regulation of the P2Y receptors under low Na(+) diet, but it revealed a pronounced axial expression of both receptors with highest abundance in surface epithelia. Thus, luminal P2Y(2) and P2Y(4) receptors and ENaC channels co-localize in surface epithelium. Intriguingly, only the stimulation of the P2Y(2) receptor mediates inhibition of electrogenic Na(+) absorption.

Role of cholinergic-activated KCa1.1 (BK), KCa3.1 (SK4) and KV7.1 (KCNQ1) channels in mouse colonic Cl- secretion

AIM

Colonic crypts are the site of Cl- secretion. Basolateral K+ channels provide the driving force for luminal cystic fibrosis transmembrane regulator-mediated Cl- exit. Relevant colonic epithelial K+ channels are the intermediate conductance Ca2+-activated K(Ca)3.1 (SK4) channel and the cAMP-activated K(V)7.1 (KCNQ1) channel. In addition, big conductance Ca2+-activated K(Ca)1.1 (BK) channels may play a role in Ca2+-activated Cl- secretion. Here we use K(Ca)1.1 and K(Ca)3.1 knock-out mice, and the K(V)7.1 channel inhibitor 293B (10 microm) to investigate the role of K(Ca)1.1, K(Ca)3.1 and K(V)7.1 channels in cholinergic-stimulated Cl- secretion.

METHODS

A Ussing chamber was used to quantify agonist-stimulated increases in short circuit current (Isc) in distal colon. Chloride secretion was activated by bl. forskolin (FSK, 2 microm) followed by bl. carbachol (CCH, 100 microm). Luminal Ba2+ (5 mm) was used to inhibit K(Ca)1.1 channels.

RESULTS

K(Ca)1.1 WT and KO mice displayed identical FSK and CCH-stimulated Isc changes, indicating that K(Ca)1.1 channels are not involved in FSK- and cholinergic-stimulated Cl- secretion. CCH-stimulated DeltaIsc was significantly reduced in K(Ca)3.1 KO mice, underscoring the known relevance of this channel in the activation of Cl- secretion by an intracellular Ca2+ increasing agonist. The residual CCH effect observed in K(Ca)3.1 KO mice suggests that yet another K+ channel is driving the CCH-stimulated Cl- secretion. In the presence of the specific K(V)7.1 channel blocker 293B, the residual CCH effect was abolished.

CONCLUSIONS

This demonstrates that both K(Ca)3.1 and K(V)7.1 channels are activated by cholinergic agonists and drive Cl- secretion. In contrast, K(Ca)1.1 channels are not involved in stimulated electrogenic Cl- secretion.

Knock-out mice reveal the contributions of P2Y and P2X receptors to nucleotide-induced Ca2+ signaling in macrophages

Immune cell function is modulated by changes in extracellular nucleotide levels. Here we used reverse transcription-PCR analyses, single cell Ca2+ imaging, and knock-out mice to define the receptors mediating nucleotide-induced Ca2+ signaling in resident peritoneal macrophages. In Ca2+-free buffer, the potent (K0.5<1 microm) stimulatory effect of UTP (or ATP) on endoplasmic reticulum (ER) Ca2+ release was abolished in cells isolated from P2Y2/P2Y4 double knock-out mice. Moreover, P2Y4(0/-), but not P2Y2-/-, macrophages responded to UTP. In P2Y2-/- macrophages, we could elicit Ca2+ responses to "pure" P2X receptor activation by applying ATP in buffer containing Ca2+. Purified UDP and ADP were ineffective agonists, although modest UDP-induced Ca2+ responses could be elicited in macrophages after "activation" with lipopolysaccharide and interferon-gamma. Notably, in Ca2+-free buffer, UTP-induced Ca2+ transients decayed within 1 min, and there was no response to repeated agonist challenge. Measurements of ER [Ca2+] with mag-fluo-4 showed that ER Ca2+ stores were depleted under these conditions. When extracellular Ca2+ was available, ER Ca2+ stores refilled, but Ca2+ increased to only approximately 40% of the initial value upon repeated UTP challenge. This apparent receptor desensitization persisted in GRK2+/- and GRK6-/- macrophages and after inhibition of candidate kinases protein kinase C and calmodulin-dependent kinase II. Initial challenge with UTP also reduced Ca2+ mobilization by complement component C5a (and vice versa). In conclusion, homologous receptor desensitization is not the major mechanism that rapidly dampens Ca2+ signaling mediated by P2Y2, the sole Gq-coupled receptor for UTP or ATP in macrophages. UDP responsiveness (P2Y6 receptor expression) increases following macrophage activation.

Distal Colonic K+ Secretion Occurs via BK Channels

K(+) secretion in the kidney and distal colon is a main determinant of K(+) homeostasis. This study investigated the identity of the relevant luminal secretory K(+) ion channel in distal colon. An Ussing chamber was used to measure ion transport in the recently generated BK channel-deficient (BK(-/-)) mice. BK(-/-) mice display a significant colonic epithelial phenotype with (1) lack of Ba(2+)-sensitive resting K(+) secretion, (2) absence of K(+) secretion stimulated by luminal P2Y(2) and P2Y(4) receptors, (3) absence of luminal Ca(2+) ionophore (A23187)-stimulated K(+) secretion, (4) reduced K(+) and increased Na(+) contents in feces, and (5) an increased colonic Na(+) absorption. In contrast, resting and uridine triphosphate (UTP)-stimulated K(+) secretion was not altered in mice that were deficient for the intermediate conductance Ca(2+)-activated K(+) channel SK4. BK channels localize to the luminal membrane of crypt, and reverse transcription-PCR results confirm the expression of the BK channel alpha-subunit in isolated distal colonic crypts. It is concluded that BK channels are the responsible K(+) channels for resting and stimulated Ca(2+)-activated K(+) secretion in mouse distal colon.

K+ secretion activated by luminal P2Y2 and P2Y4 receptors in mouse colon

Extracellular nucleotides are important regulators of epithelial ion transport, frequently exerting their action from the luminal side. Luminal P2Y receptors have previously been identified in rat distal colonic mucosa. Their activation by UTP and ATP stimulates K+ secretion. The aim of this study was to clarify which of the P2Y receptor subtypes are responsible for the stimulated K+ secretion. To this end P2Y2 and P2Y4 knock-out mice were used to measure distal colonic ion transport in an Ussing chamber. In mouse (NMRI) distal colonic mucosa, luminal UTP and ATP with similar potency induced a rapid and transient increase of the transepithelial voltage (V(te)) (UTP: from -0.81 +/- 0.23 to 3.11 +/- 0.61 mV, n = 24), an increase of equivalent short circuit current (I(sc)) by 166.9 +/- 22.8 microA cm(-2) and a decrease of transepithelial resistance (R(te)) from 29.4 +/- 2.4 to 23.5 +/- 2.0 Omega cm2. This effect was completely inhibited by luminal Ba2+ (5 mm, n = 5) and iberiotoxin (240 nm, n = 6), indicating UTP/ATP-stimulated K+ secretion. RT-PCR analysis of isolated colonic crypts revealed P2Y2, P2Y4 and P2Y6 specific transcripts. The luminal UTP-stimulated K+ secretion was still present in P2Y2 receptor knock-out mice, but significantly reduced (DeltaV(te): 0.83 +/- 0.26 mV) compared to wild-type littermates (DeltaV(te): 2.08 +/- 0.52 mV, n = 9). In P2Y4 receptor knock-out mice the UTP-induced K+ secretion was similarly reduced. Luminal UTP-stimulated K+ secretion was completely absent in P2Y2/P2Y4 double receptor KO mice. Basolateral UTP showed no effect. In summary, these results indicate that both the P2Y2 and P2Y4 receptors are present in the luminal membrane of mouse distal colonic mucosa, and stimulation of these receptors leads to K+ secretion.

Lecithinase reaction of Staphylococcus aureus strains of different origin on Baird-Parker medium

Staphylococcus aureus produces one or more enzymes with lipolytic activity, but differences between strains have been reported (Owens and John 1975; O'Toole 1987; Rollof et al. 1987). The biological and biochemical properties of these enzymes have been investigated and results were recently reviewed (Kötting et al. 1984). Baird-Parker medium (Baird-Parker 1962) is a selective medium commonly used for the isolation of Staph. aureus. The presence of egg yolk in this medium permits the detection of two reactions due to lipolytic activity of staphylococci: (1) Lecithinase reaction, a zone of precipitate in the medium surrounding the colonies; and (2) Lipase reaction or 'pearly layer', an iridescent film in and immediately surrounding colonies, visible by reflected light (iridescent sheen or 'oil in water'). In this study, human and bovine strains, previously biotyped according to the scheme of Devriese et al. (1984), were compared for production of a zone of precipitation, lecithinase reaction, on Baird-Parker medium. Bovine and human strains of Staph. aureus were compared for production of the egg yolk reaction (lecithinase reaction) on Baird-Parker medium and the results were related to their biotypes and site of origin of the sample. Human strains and strains biotyped as human biotypes had higher percentage of positive results than bovine isolates and/or biotypes. However, all strains isolated from body sites of heifers produced a positive reaction regardless of the biotype.

Isolation and identification of coagulase-negative Staphylococcus species from bovine body sites and streak canals of nulliparous heifers

Heifers (n = 103) ranging in age from 1d to 2 yr were sampled to determine the coagulase-negative staphylococcal flora of haircoat, nares, vagina, teat skin, and streak canal. A total of 2706 staphylococal strains were identified from 3612 bacterial isolates. Other genera or groups identified included Bacillus, Micrococcus, Corynebacterium, and coliforms. Staphylococci were identified utilizing a simplified biochemical scheme. Staphylococcus xylosus, S. chromogenes, and S. warneri were the predominant species recovered from anatomic sites and streak canal. Staphylococcal strains identified from specific body sites (expressed as percentage of heifers harboring these species) were: nares 74% S. xylosus and 48% S. warneri; haircoat, 70% S. xylosus and 57% S. chromogenes; vagina, 60% S. chromogenes and 54% S. xylosus; teat skin 62% S. chromogenes and 61% S. warneri; streak canal 53% S. chromogenes, and 43% S. warneri. The prevalent staphylococcal strains identified differed from heifers in confined housing compared with heifers on pasture. Differences observed in distribution of Staphylococcus species among body sites, particularly those between teat skin and streak canal, suggest that establishment of staphylococcal microflora depends on the ability of a species to adapt to and colonize anatomic sites as well as on environmental conditions present.