Bitter taste receptor function in asthmatic and nonasthmatic human airway smooth muscle cells.

Bitter taste receptors (TAS2Rs) have recently been found to be expressed on human airway smooth muscle (HASM), and their activation results in marked relaxation. These agents have been proposed as a new class of bronchodilators in the treatment of obstructive lung diseases because they act via a different mechanism than ß-agonists. The TAS2R signal transduction pathway in HASM has multiple elements that are potentially subject to regulation by inflammatory, genetic, and epigenetic mechanisms associated with asthma. To address this, expression, signaling, and physiologic functions of the three major TAS2Rs (subtypes 10, 14, and 31) on HASM were studied. Transcript expression of these TAS2Rs was not decreased in HASM cells derived from donors with asthma compared with those without asthma (n = 6 from each group). In addition, intracellular calcium ([Ca(2+)]i) signaling using TAS2R subtype-specific agonists (diphenhydramine, chloroquine, saccharin, and flufenamic acid) was not impaired in the cells derived from donors with asthma, nor was the response to quinine, which activates all three subtypes. HASM cell mechanics measured by magnetic twisting cytometry revealed equivalent TAS2R-mediated relaxation of methacholine-treated cells between the two groups. Human precision-cut lung slices treated with IL-13 caused a decrease in ß-agonist (formoterol)-mediated relaxation of carbachol-contracted airways compared with control slices. In contrast, TAS2R-mediated relaxation was unaffected by IL-13. We conclude that TAS2R expression or function is unaffected in HASM cells derived from patients with asthma or the IL-13 inflammatory environment.

Impact of Palliative Care on Interhospital Transfers to the Intensive Care Unit.

Community hospitals will often transfer their most complex, critically ill patients to intensive care units (ICUs) of tertiary care centers for specialized, comprehensive care. This population of patients has high rates of morbidity and mortality. Palliative care involvement in critically ill patients has been demonstrated to reduce over-utilization of resources and hospital length of stays. We hypothesized that transfers from community hospitals had low rates of palliative care involvement and high utilization of ICU resources. In this single-center retrospective cohort study, 848 patients transferred from local community hospitals to the medical ICU (MICU) and cardiac care unit (CCU) at a tertiary care center between 2016-2018 were analyzed for patient disposition, length of stay, hospitalization cost, and time to palliative care consultation. Of the 848 patients, 484 (57.1%) expired, with 117 (13.8%) having expired within 48 hours of transfer. Palliative care consult was placed for 201 (23.7%) patients. Patients with palliative care consult were statistically more likely to be referred to hospice (p<0.001). Over two-thirds of palliative care consults were placed later than 5 days after transfer. Time to palliative care consult was positively correlated with length of hospitalization among MICU patients (r=0.79) and CCU patients (r=0.90). Time to palliative consult was also positively correlated with hospitalization cost among MICU patients (r=0.75) and CCU patients (r=0.86). These results indicate early palliative care consultation in this population may result in timely goals of care discussions and optimization of resources.

Agonist-promoted homologous desensitization of human airway smooth muscle bitter taste receptors.

Bitter taste receptors (TAS2Rs) were shown to be expressed in human airway smooth muscle (ASM). They couple to specialized [Ca(2+)](i) release, leading to membrane hyperpolarization, the relaxation of ASM, and marked bronchodilation. TAS2Rs are G-protein-coupled receptors, known to undergo rapid agonist-promoted desensitization that can limit therapeutic efficacy. Because TAS2Rs represent a new drug target for treating obstructive lung disease, we investigated their capacity for rapid desensitization, and assessed their potential mechanisms. The pretreatment of human ASM cells with the prototypic TAS2R agonist quinine resulted in a 31% ± 5.1% desensitization of the [Ca(2+)](i) response from a subsequent exposure to quinine. No significant change in the endothelin-stimulated [Ca(2+)](i) response was attributed to the short-term use of quinine, indicating a homologous form of desensitization. The TAS2R agonist saccharin also evoked desensitization, and cross-compound desensitization with quinine was evident. Desensitization of the [Ca(2+)](i) response was attenuated by a dynamin inhibitor, suggesting that receptor internalization (a G-protein coupled receptor kinase [GRK]-mediated, ß-arrestin-mediated process) plays an integral role in the desensitization of TAS2R. Desensitization was insensitive to antagonists of the second messenger kinases protein kinase A and protein kinase C. Using intact airways, short-term, agonist-promoted TAS2R desensitization of the relaxation response was also observed. Thus these receptors, which represent a potential novel target for direct bronchodilators, undergo a modest degree of agonist-promoted desensitization that may affect clinical efficacy. Collectively, the results of these mechanistic studies, along with the multiple serines and threonines in intracellular loop 3 and the cytoplasmic tail of TAS2Rs, suggest a GRK-mediated mode of desensitization.

Granulomatous Pneumocystis jiroveci Pneumonia in an HIV-Positive Patient on Antiretroviral Therapy: A Diagnostic Challenge.

Human Immunodeficiency Virus (HIV)-related Opportunistic Infections (OI), including Pneumocystis jiroveci pneumonia (PCP), have become much less commonplace with anti-retroviral therapy (ART). Despite this, OIs are still common and it is important to remain vigilant for their presence and be aware of how ART and OI chemoprophylaxis may lead to atypical disease presentations. We present the case of a 51-year-old woman with HIV and CD4+ T helper lymphocytes cell count > 200 cells/ul on both ART and trimethoprim/sulfamethoxazole prophylaxis who presented with cavitating lung masses, mediastinal lymphadenopathy and pleural effusions. Negative bronchoalveolar lavage (BAL) and transbronchial biopsy (TBBx) prompted a second diagnostic procedure with a transthoracic core needle biopsy; the final diagnosis was granulomatous PCP. This case showcases a very rare presentation of PCP, with both large cavitating lung masses on imaging and granulomatous reaction on pathology, as well as the challenge of a potentially missed diagnosis with negative BAL and TBBx requiring transthoracic core needle biopsy for a final diagnosis.

Atraumatic Splenic Rupture Associated with Influenza A (H1N1) Pneumonia: Case Report and Review of the Literature.

Influenza virus infection may present with fever, chills, headache, myalgia, malaise, and respiratory symptoms, with a few cases developing into pneumonia, respiratory failure, and other organ damage. Very few cases of atraumatic splenic rupture associated with influenza infection have been reported. Atraumatic splenic rupture, while rare, is associated with high mortality. Here, we report the first case of atraumatic splenic rupture associated with influenza infection in the English literature and review the prior reported literature. The patient was diagnosed with influenza A (H1N1) pneumonia and subsequently developed hemorrhagic shock requiring emergency laparotomy and removal of the ruptured spleen.

Invasive aspergillosis masquerading as catastrophic antiphospholipid syndrome.

A 25-year-old woman with a history of systemic lupus erythematosus who was taking steroids came to the hospital because of vague signs and symptoms of weight loss, constipation, and oral ulcers. Multiorgan dysfunction developed, and catastrophic antiphospholipid syndrome was suspected. She was treated with an intravenous infusion of heparin, but she experienced a subdural hemorrhage and died on day 10 of the hospitalization. An autopsy revealed disseminated invasive aspergillosis. This case illustrates that invasive aspergillosis is a frequently missed diagnosis and should be part of the differential diagnosis for any patient who is immunosuppressed, including patients with autoimmune diseases such as systemic lupus erythematosus.

Integrin α9ß1 in airway smooth muscle suppresses exaggerated airway narrowing.

Exaggerated contraction of airway smooth muscle is the major cause of symptoms in asthma, but the mechanisms that prevent exaggerated contraction are incompletely understood. Here, we showed that integrin α9ß1 on airway smooth muscle localizes the polyamine catabolizing enzyme spermidine/spermine N1-acetyltransferase (SSAT) in close proximity to the lipid kinase PIP5K1γ. As PIP5K1γ is the major source of PIP2 in airway smooth muscle and its activity is regulated by higher-order polyamines, this interaction inhibited IP3-dependent airway smooth muscle contraction. Mice lacking integrin α9ß1 in smooth muscle had increased airway responsiveness in vivo, and loss or inhibition of integrin α9ß1 increased in vitro airway narrowing and airway smooth muscle contraction in murine and human airways. Contraction was enhanced in control airways by the higher-order polyamine spermine or by cell-permeable PIP2, but these interventions had no effect on airways lacking integrin α9ß1 or treated with integrin α9ß1-blocking antibodies. Enhancement of SSAT activity or knockdown of PIP5K1γ inhibited airway contraction, but only in the presence of functional integrin α9ß1. Therefore, integrin α9ß1 appears to serve as a brake on airway smooth muscle contraction by recruiting SSAT, which facilitates local catabolism of polyamines and thereby inhibits PIP5K1γ. Targeting key components of this pathway could thus lead to new treatment strategies for asthma.

Bitter taste receptors on airway smooth muscle bronchodilate by localized calcium signaling and reverse obstruction.

Bitter taste receptors (TAS2Rs) on the tongue probably evolved to evoke signals for avoiding ingestion of plant toxins. We found expression of TAS2Rs on human airway smooth muscle (ASM) and considered these to be avoidance receptors for inhalants that, when activated, lead to ASM contraction and bronchospasm. TAS2R agonists such as saccharin, chloroquine and denatonium evoked increased intracellular calcium ([Ca²(+)](i)) in ASM in a Gßγ-, phospholipase Cß (PLCß)- and inositol trisphosphate (IP3) receptor-dependent manner, which would be expected to evoke contraction. Paradoxically, bitter tastants caused relaxation of isolated ASM and dilation of airways that was threefold greater than that elicited by ß-adrenergic receptor agonists. The relaxation induced by TAS2Rs is associated with a localized [Ca²(+)](i) response at the cell membrane, which opens large-conductance Ca²(+)-activated K(+) (BK(Ca)) channels, leading to ASM membrane hyperpolarization. Inhaled bitter tastants decreased airway obstruction in a mouse model of asthma. Given the need for efficacious bronchodilators for treating obstructive lung diseases, this pathway can be exploited for therapy with the thousands of known synthetic and naturally occurring bitter tastants.