Cystic Fibrosis Transmembrane Regulator Research Articles

Nutritional support for adult сystic fibrosis patients receiving targeted treatment

Cystic fibrosis (CF) is characterized by the development of a severe nutritional deficiency. A low BMI directly correlates with low lung function and requires active nutritional support. Pathogenetic (targeted) therapy aimed at restoring the chlorine channel function also leads to weight gain. The effects of CFTR modulators on extrapulmonary pathology in adult CF patients in Russia have been described very little.Aim. To evaluate the sequential impact of two targeted drugs – the potentiator ivacaftor and the triple combination of CF transmembrane regulator modulators elexacaftor/tezacaftor/ivacaftor – on the nutritional status of an adult patient with cystic fibrosis receiving nutritional support.Conclusion. Therapy with CFTR modulator in combination with sipping nutritional support promotes significant weight gain in adult CF patients. The triple combination of elexacaftor/tezacaftor/ivacaftor has a more active effect on nutritional status than ivacaftor alone. The targeted therapy requires supervision by a nutritionist.

Exploring perceptions of and decision-making about CFTR modulators.

Cystic fibrosis (CF)treatment has increasingly focused on highly effective modulators. Despite measurable benefits of modulators, there is little guidance for CF care team members on providing education and support to patients regarding initiation of these therapies. We aimed to explore patient, caregiver, and clinician perceptions of modulators and influences on decisions about starting cystic fibrosis transmembrane regulator (CFTR) modulators. We conducted semistructured interviews with CF clinicians, adults with CF, and caregivers of children with CF. We reviewed audio recordings and coded responses to identify central themes. We interviewed 8 CF clinicians, 9 adults with CF, and 11 caregivers of children with CF. Themes centered on emotional responses to modulator availability, influences on decision-making, concerns about side effects, impact of modulators on planning for the future, the benefits of the multidisciplinary CF care team in supporting treatment decisions, and the unique needs of people with CF who are not eligible for modulators. Clinicians described changes in conversations about modulators since the approval of elexacaftor/tezacaftor/ivacaftor, specifically greater willingness to prescribe with less nuanced conversations with patients and/or caregivers regarding their use. Based on perspectives and experiences of CF clinicians, adults with CF, and caregivers of children with CF, we suggest clinicians approach conversations about CFTR modulators thoughtfully and thoroughly, utilizing the multidisciplinary model of CF care in exploring patient and caregiver emotions while filling in knowledge gaps, asking about treatment goals beyond potential clinical benefit, and having compassionate conversations with those who are ineligible for modulators.

Comparing ATPase activity of ATP-binding cassette subfamily C member 4, lamprey CFTR, and human CFTR using an antimony-phosphomolybdate assay.

Introduction: ATP-binding cassette (ABC) transporters use the hydrolysis of ATP to power the active transport of molecules, but paradoxically the cystic fibrosis transmembrane regulator (CFTR, ABCC7) forms an ion channel. We previously showed that ATP-binding cassette subfamily C member 4 (ABCC4) is the closest mammalian paralog to CFTR, compared to other ABC transporters. In addition, Lamprey CFTR (Lp-CFTR) is the oldest known CFTR ortholog and has unique structural and functional features compared to human CFTR (hCFTR). The availability of these evolutionarily distant orthologs gives us the opportunity to study the changes in ATPase activity that may be related to their disparate functions. Methods: We utilized the baculovirus expression system with Sf9 insect cells and made use of the highly sensitive antimony-phosphomolybdate assay for testing the ATPase activity of human ABCC4 (hABCC4), Lp-CFTR, and hCFTR under similar experimental conditions. This assay measures the production of inorganic phosphate (Pi) in the nanomolar range. Results: Crude plasma membranes were purified, and protein concentration, determined semi-quantitatively, of hABCC4, Lp-CFTR, and hCFTR ranged from 0.01 to 0.36μg/μL. No significant difference in expression level was found although hABCC4 trended toward the highest level. hABCC4 was activated by ATP with the equilibrium constant (Kd) 0.55 ± 0.28mM (n = 8). Estimated maximum ATPase rate (Vmax) for hABCC4 was about 0.2nmol/μg/min when the protein was activated with 1mM ATP at 37°C (n = 7). Estimated maximum ATPase rate for PKA-phosphorylated Lp-CFTR reached about half of hCFTR levels in the same conditions. Vmax for both Lp-CFTR and hCFTR were significantly increased in high PKA conditions compared to low PKA conditions. Maximum intrinsic ATPase rate of hABCC4 in the absence of substrate was twice that of hCFTR when activated in 1mM ATP. Conclusion: The findings here suggest that while both ABCC4 and hCFTR bear one consensus and one degenerate ATPase site, the hCFTR exhibited a reduced intrinsic ATPase activity. In addition, ATPase activity in the CFTR lineage increased from Lp-CFTR to hCFTR. Finally, the studies pave the way to purify hABCC4, Lp-CFTR, and hCFTR from Sf9 cells for their structural investigation, including by cryo-EM, and for studies of evolution in the ABC transporter superfamily.

Cadmium transport by mammalian ATP-binding cassette transporters.

Cellular responses to toxic metals depend on metal accessibility to intracellular targets, reaching interaction sites, and the intracellular metal concentration, which is mainly determined by uptake pathways, binding/sequestration and efflux pathways. ATP-binding cassette (ABC) transporters are ubiquitous in the human body-usually in epithelia-and are responsible for the transfer of indispensable physiological substrates(e.g. lipids and heme), protection against potentially toxic substances, maintenance of fluid composition, and excretion of metabolic waste products. Derailed regulation and gene variants of ABC transporters culminate in a wide array of pathophysiological disease states, such as oncogenic multidrug resistance or cystic fibrosis. Cadmium (Cd) has no known physiological role in mammalians and poses a health risk due to its release into the environment as a result of industrial activities, and eventually passes into the food chain. Epithelial cells, especially within the liver, lungs, gastrointestinal tract and kidneys, are particularly susceptible to the multifaceted effects of Cd because of the plethora of uptake pathways available. Pertinent to their broad substrate spectra, ABC transporters represent a major cellular efflux pathway for Cd and Cd complexes. In this review, we summarize current knowledge concerning transport of Cd and its complexes (mainly Cd bound to glutathione) by the ABC transporters ABCB1 (P-glycoprotein, MDR1), ABCB6, ABCC1 (multidrug resistance related protein 1, MRP1), ABCC7 (cystic fibrosis transmembrane regulator, CFTR), and ABCG2 (breast cancer related protein, BCRP). Potential detoxification strategies underlying ABC transporter-mediated efflux of Cd and Cd complexesare discussed.

Cystic Fibrosis Transmembrane Regulator Modulator Therapy Perspective: Findings in Clinical Outcomes in a Series of Pediatric Patients

Cystic Fibrosis (CF) is the most frequent autosomal recessive disorder in Caucasians and has reduced life expectancy. It is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene which results in impairment of production, expression, and trafficking of the CFTR protein. CF has a multifaceted clinical representation with respiratory involvement as a main cause of morbidity and mortality. The multidisciplinary approach, care in specialized centers, early diagnosis through neonatal screening, and development of symptomatic treatments improved survival in the last decades. CFTR modulators were developed based on the discovery of the CF gene in 1989 and the improvement of genetic testing and have changed the perspective of a debilitating disease. These therapies, acting more upstream in the pathogenic cascade, overcome the underlying dysfunctions caused by CFTR mutations, having the ability to enhance or restore the resulting functional effects. CFTR modulator therapies are highly effective treatments for cystic fibrosis patients as shown in many clinical trials and real-life analyses so far. Improvement of quality of life, lung function, and pulmonary exacerbation rates are indisputable targets when evaluating the efficacy and efficiency of medical interventions in such a disease as CF, and they have been substantially changed in the era of modulators. We analyzed a small group of patients who were initiated on Kaftrio as per the indicated protocol. All significant clinical and functional aspects were improved, demonstrating the disease-changing potential of this therapy. We did not observe threatening side effects, no patients were stopped from the medication. CFTR modulators are the beginning of a new era in CF, a perspective for the improvement and effectiveness of precision medicine in CF patients.

Effects of Social Determinants of Health on Clinical Outcomes in Pediatric Cystic Fibrosis Patients

Background and Objective: 
 Advances in the treatment of cystic fibrosis (CF) with cystic fibrosis transmembrane regulator modulators have improved morbidity and mortality, however, clinical outcomes vary among genetically similar patients due to contributions of social determinants of health (SDOH). Pancreatic insufficiency, CF-related diabetes (CFRD), Pseudomonas infections, and lower BMI increase risk of severe lung disease, measured by forced expiratory volume in 1 second (FEV1). This project aims to identify socially vulnerable patients and evaluate the impact of SDOH on clinical outcomes. 
 Methods: 
 From January to July 2023, SDOH screeners were distributed to families of children with CF at Riley Hospital for Children, documenting transportation, housing, food insecurity, insurance, and medication costs. Clinical outcomes for each patient including FEV1% predicted, BMI/WFL percentile, CFRD, hospitalizations, respiratory infections with Pseudomonas aeruginosa, and pancreatic insufficiency within the past 12 months were recorded. Patients were categorized by SDOH vulnerability, and associations with poor clinical outcomes were analyzed using the Chi-squared test of independence. 
 Results: 
 A total of 193 screeners were analyzed: males represented 52.6% of the cohort, 2.60% identified as non-white race, and 3.65% reported Hispanic ethnicity. Overall, 51.8% screened positive for at least one SDOH (SDOH+) and 48.1% screened negative (SDOH-). The average FEV1% predicted decline among SDOH+ patients was 5.79% and 3.51% among SDOH- patients. SDOH+ patients were more likely to have at least a 5% decline in FEV1% predicted (p=0.037) and to be hospitalized due to exacerbations of CF lung disease at least once in the past 12 months (p=0.030). Although low BMI percentile, Pseudomonas infection, and CFRD were not significantly associated with SDOH, socially vulnerable patients demonstrated higher rates of these clinical outcomes. 
 Conclusion and Clinical Implications: 
 SDOH impact CF clinical outcomes. Screeners are effective in identifying socially vulnerable patients and serve as the first step in addressing unmet social needs. 

Association between cystic fibrosis transmembrane regulator genotype and clinical outcomes, glucose homeostasis indices and CF-related diabetes risk in adults with CF.

People living with cystic fibrosis (pwCF) homozygous for F508del present more severe phenotypes. PwCF with compound heterozygous genotypes F508del /A455E and F508del /L206W may have milder cystic fibrosis (CF) phenotypes. We compared F508del homozygotes and common compound heterozygotes (F508del and a second pathogenic variant) in adult patients. Nutritional, pulmonary function and glucose homeostasis indices data were collected from the prospective Montreal CF cohort. Two-hundred and three adults with CF having at least one F508del variant were included. Individuals were divided into subgroups: homozygous F508del/F508del (n=149); F508del/621+1G>T (n=17); F508del/711+1G>T (n=11); F508del/A455E (n=12); and F508del/L206W (n=14). Subgroups with the F508del/L206W and F508del/A455E had a lower proportion with pancreatic exocrine insufficiency (p<0.0001), a higher fat mass (p<0.0001), and lower glucose area under the curve (AUC) (p=0.027). The F508del/L206W subgroup had significantly higher insulin secretion (AUC; p=0.027) and body mass index (p<0.001). Pulmonary function (FEV1) was significantly higher for the F508del/L206W subgroup (p<0.0001). Over a median of 7.37 years, the risk of developing CFRD in 141 patients was similar between groups. PwCF with heterozygous F508del/L206W and F508del/A455E tended to have pancreatic exocrine sufficiency, better nutritional status, improved pulmonary function and better diabetogenic indices, but this does not translate into lower risk of CF-related Diabetes.

Transcriptional regulation of esophageal, intestinal, and branchial solute transporters by salinity, growth hormone, and cortisol in Atlantic salmon.

In marine habitats, Atlantic salmon (Salmo salar) imbibe seawater (SW) to replace body water that is passively lost to the ambient environment. By desalinating consumed SW, the esophagus enables solute-linked water absorption across the intestinal epithelium. The processes underlying esophageal desalination in salmon and their hormonal regulation during smoltification and following SW exposure are unresolved. To address this, we considered whether two Na+ /H+ exchangers (Nhe2 and -3) expressed in the esophagus contribute to the uptake of Na+ from lumenal SW. There were no seasonal changes in esophageal nhe2 or -3 expression during smoltification; however, nhe3 increased following 48 h of SW exposure in May. Esophageal nhe2, -3, and growth hormone receptor b1 were elevated in smolts acclimated to SW for 2.5 weeks. Treatment with cortisol stimulated branchial Na+ /K+ -ATPase (Nka) activity, and Na+ /K+ /2Cl- cotransporter 1 (nkcc1), cystic fibrosis transmembrane regulator 1 (cftr1), and nka-α1b expression. Esophageal nhe2, but not nhe3 expression, was stimulated by cortisol. In anterior intestine, cortisol stimulated nkcc2, cftr2, and nka-α1b. Our findings indicate that salinity stimulates esophageal nhe2 and -3, and that cortisol coordinates the expression of esophageal, intestinal, and branchial solute transporters to support the SW adaptability of Atlantic salmon.

Drug-induced psychiatric disorders: A pharmacovigilance update

The psychiatric risks associated with drugs are sometimes one of the few restrictions on the use of certain drug classes, such as corticosteroids in patients with a history of severe psychotic episodes associated with this drug class. In this non-exhaustive review, we propose to deal with the most recent issues concerning psychiatric disorders induced by drugs and encountered in doctors' clinical practice. Firstly, we look at depressive disorders and suicide risks, secondly at psychotic and manic disorders and thirdly at anxiety and sleep disorders. While lot of drugs are associated with psychiatric disorders, the confounding by indication represents an important methodological gap since information on the psychiatric profile of patients is not always available. This is particularly the case for serotonin reuptake inhibitors and esketamine used as antidepressants. Recent pharmacovigilance concerns of psychiatric disorders emerged with montelukast, orexin receptor antagonists or cystic fibrosis transmembrane regulator (CFTR) modulators.

Use of CFTR modulators in special populations, part 2: Severe lung disease.

Safety and efficacy data surrounding cystic fibrosistransmembrane regulator(CFTR) modulator administration for people with CF (pwCF) and severe lung disease elect has remained unclear as a result of exclusion from key trials.A scoping review of English language articles from the period of 1 January2012, to 31 July2023 was conducted utilizing PubMed and EmBase databases with the following terms: "severe lung disease" OR "advanced lung disease" AND "ivacaftor OR lumacaftor OR tezacaftor OR elexacaftor"; "cystic fibrosis transmembrane conductance regulator" AND "off label drug use." Search results were reviewed by title and abstract for relevance.Twenty articles specific to CFTR modulator use in the setting of severe lung disease were included for review, with few specific to pediatric-aged pwCF. PwCF and severe lung disease experienced significant improvement in pulmonary function, body weight, number of IV antibiotic days, and quality of life. A few studies reported a transient decline in pulmonary function among pwCF shortly after LUM/IVA initiation. However, preemptive reductions in the dose of LUM/IVA may mitigate this reaction. ELE/TEZ/IVA utilization in pwCF and severe lung disease appears to be devoid of the transient decline in pulmonary function observed with LUM/IVA while providing the same clinical benefit.Current available data regarding use of CFTR modulators in pwCF and severe lung disease is reassuring; however, there remains a lack data regarding outcomes among the pediatric population including long-term outcomes. Therefore, treatment decisions should be individualized and coproduced.

Delivering a New Future for People With Cystic Fibrosis.

Treatment, prognosis, and quality of life for people with cystic fibrosis (CF) have improved steadily since the initial description of the disease, but most dramatically in the past decade. In 2021, the median predicted survival increased to 53 years, compared with 17 years in 1970. The recent improvement in outcomes is attributable to the advent of cystic fibrosis transmembrane regulator (CFTR) modulators, small molecules that enhance the function of defective CFTR protein. The first CFTR modulator, ivacaftor, received Food and Drug Administration approval in 2011 to treat a single CFTR variant, comprising only 4% of those affected by CF. With the demonstration of efficacy, drug approval has been expanded to other variants. Multiple CFTR modulators used in combination with ivacaftor augment efficacy and increase the number of CFTR variants amenable to therapy. Approval of elexecaftor/tezecaftor/ivacaftor in 2019 increased the number of individuals who could benefit from highly effective modulator therapy (HEMT) to ∼90% of the CF population in the United States. HEMT has been dramatically effective, with overall improvements in lung function, quality of life, nutritional status, and, in women, increased fertility. HEMT may delay the onset of other CF-related comorbidities. Although off-target effects, including hepatotoxicity, drug-drug interactions, and putative mental health issues can complicate use, modulator therapy has been generally well tolerated. Ten percent of people with CF have variants that are not amenable to modulator treatment. HEMT, despite its great cost and limited global access, has brought legitimate hope and changed the lives of a significant majority of individuals and families affected by CF in North America.

Effect of 18 months elexacaftor-tezacaftor-ivacaftor on body mass index and glycemic control in adults with cystic fibrosis

Malnutrition and cystic fibrosis related diabetes (CFRD) are common comorbidities in cystic fibrosis (CF). Cystic fibrosis transmembrane regulator (CFTR) modulators have shown beneficial effects on respiratory status. This study aims to determine the effect of elexacaftor-tezacaftor-ivacaftor (ETI) on body mass index (BMI) and glycemic control. A retrospective, observational study of a cohort of 17 adult CF patients was conducted at the CF reference center of Ghent University Hospital. BMI evolution was analyzed 18 months before and 0, 3, 6, 12 and 18 months after the start of ETI. The evolution of insulin dependence and the 2h oral glucose tolerance test (OGTT) results were described until 36 months after start of ETI, in a small subgroup of ten patients with CFRD or impaired glucose tolerance (IGT). A significant increase in mean BMI of 1.2kg/m2 (±1.3 SD) was observed. Most weight gain was observed in the first 3 months after starting treatment. This effect was sustained during the observed period of 18 months. Six patients had insulin dependent CFRD, of which three were able to stop insulin after starting ETI. Two patients with CFRD treated with dietary measures showed an initial normalization of the 2h OGTT, but deterioration at 36 month follow-up. After initiation of ETI an increase in BMI was observed in adults with CF. ETI can have a beneficial impact on glucose metabolism in patients with CFRD, leading to a possible need for reduction or cessation of insulin therapy.

Health inequities in the modulator era.

To discuss the existing health inequities in people with cystic fibrosis (CF) and how the recent development of cystic fibrosis transmembrane regulator (CFTR) modulators may impact these inequities. People with CF (pwCF) from low socioeconomic status (SES) have more pulmonary exacerbations, worse nutritional status, lower pulmonary function, and an increased mortality rate with less access to lung transplantation. pwCF who identify as racial and ethnic minorities have earlier mortality, lower lung function, are less likely to be detected on newborn screening resulting in a delayed diagnosis, are underrepresented in clinic trials, and less likely to be eligible for a CFTR modulator. Female sex is associated with more pulmonary exacerbations and earlier mortality. Sexual gender minorities are a vulnerable population with worse health outcomes, and more research is needed in CF. CFTR modulators are inaccessible to low to middle-income countries due to significant cost burden. People with CF from low SES, racial and ethnic minorities, female sex, and sexual gender minorities face health inequities. CFTR modulator use will further widen existing health inequities given the unequal access to modulators based on nonqualifying genetics and exorbitant cost restricting use both on an individual and global level.

Loureirin C extracted from Dracaena cochinchinensis S.C. Chen prevents rotaviral diarrhea in mice by inhibiting the intestinal Ca2+-activated Cl− channels

Ethnopharmacological relevanceResina Draconis (RD) is the red resin of Dracaena cochinchinensis (Lour.) S.C. Chen and most used as a hemostatic drug in traditional Chinese medicine. Recent studies have reported that RD has a therapeutic effect on gastrointestinal diseases. Loureirin A, B, and C (LA, LB, and LC) are dihydrochalcone compounds isolated from RD. Aim of the studyDehydration is the primary cause of death in rotaviral diarrhea. Inhibition of Ca2+-activated Cl− channels (CaCCs)-mediated Cl− secretion significantly reduced fluid secretion in rotaviral diarrhea. RD was used to treat digestive diseases such as diarrhea and abdominal pain; however, the pharmacological mechanism remains unclear. This study investigated the effects of RD and loureirin on intestinal Cl− channels and their therapeutic effects on rotavirus-induced diarrhea, aiming to reveal RD's molecular basis, targets, and mechanisms for treating rotaviral diarrhea. Materials and methodsCell-based fluorescence quenching assays were used to examine the effect of RD and loureirin on Cl− channels activity. Electrophysiological properties were tested using short-circuit current experiments in epithelial cells or freshly isolated mouse intestinal tissue. Fecal water content, intestinal peristalsis rate, and smooth muscle contraction were measured in neonatal mice infected with SA-11 rotavirus before and after LC treatment or adult mice. ResultsRD, LA, LB, and LC inhibited CaCCs-mediated Cl− current in HT-29 cells and colonic epithelium. The inhibitory effect of LC on CaCCs was primarily on the apical side in epithelial cells, which may be partially produced by affecting cytoplasmic Ca2+ levels. LC significantly inhibited TMEM16A-mediated Cl− current. Characterization studies revealed that LC inhibited basolateral K+ channel activity without affecting Na+/K+-ATPase activity in the colonic epithelium. Although LC activated the cystic fibrosis transmembrane regulator in epithelial cells, its effect was not apparent in colonic epithelium. In vivo, LC significantly reduced the fecal water content, intestinal peristalsis rate, and smooth muscle contraction of mice infected with rotavirus. ConclusionRD and its active compound LC inhibit intestinal CaCCs activity, which might mediate the anti-rotaviral diarrheal effect of RD.

Sinus Symptoms in Cystic Fibrosis Patients and the Role of Interdisciplinary Care

Chronic rhinosinusitis (CRS) is known to occur in most cystic fibrosis (CF) patients. This phenomenon occurs because the genetic mutations in CF cause impaired chloride ion transport, which affects water transport and thus leads to thick mucus that cannot be cleared easily in both the lower and upper airways. While improvements continue to be made in treatment modalities for CF patients in terms of modulator therapies, the effect on sinus disease symptoms and the role of the otolaryngologist (ENT) continues to evolve. This study investigates the sinus symptoms of CF patients with comparison to ENT involvement in their care, the histories of polyps and sinus surgeries of these CF patients, and how their initiation to modulator treatment has affected ENT involvement in their care. A retrospective health records review was conducted including patients from Augusta University Adult Cystic Fibrosis Center with stratification based on demographics, mutations, modulators, ENT clinic visits, history of polyps or nasal surgery, and reported symptoms of headaches, olfactory dysfunction, and sleep problems. 98 patients of the Augusta University Adult Cystic Fibrosis Center met the inclusion criteria of this study. Most of the patients with reported ENT visits in the past 10 years were white and between the ages of 20-29. The most common modulator therapy of the CF patients was elexacaftor-tezacaftor-ivacaftor at 72.22%. More than half of the patients had a history of sinonasal surgery, and almost half had a history of polyps. In comparing ENT visits to the initiation of modulator therapy, 24% of the patients with reported ENT visits saw an ENT after starting modulator therapy. CRS can contribute to morbidity in CF patients with most patients requiring surgical intervention in their lifetime. Additionally, persistent sinonasal symptoms can reduce the quality of life in CF patients. Despite treatment with modulator therapies, otolaryngologists continue to have a role in interdisciplinary CF management.CF- Cystic Fibrosis; CFTR- Cystic Fibrosis Transmembrane Regulator; CRS- Chronic Rhinosinusitis; EMR- Electronic Medical Record; ENT- Otolaryngologist

Synthesis and Evaluation of Bithiazole Derivatives As Potential α-Sarcoglycan Correctors.

4'-Methyl-4,5'-bithiazoles were previously identified as cystic fibrosis transmembrane regulator (CFTR) correctors, thus being able to correct folding defective mutants of the channel regulating chloride transport through the membrane. Additionally, bithiazole derivative C17 was reported to recover α-sarcoglycan in vitro and in vivo. We report here the synthesis of two new derivatives of C17, in which the two sides of the bithiazole scaffold were modified. The synthesized compounds and the corresponding precursors were tested in myogenic cells to evaluate the expression of α-sarcoglycan. The results highlighted that both substitutions of the bithiazole scaffold are important to achieve the maximum recovery of the α-sarcoglycan mutant. Nonetheless, partial preservation of the activity was observed. Accordingly, this paves the way to further derivatizations/optimization and target fishing studies, which were preliminarily performed in this study as a proof of concept, allowing the investigation of the molecular mechanisms leading to the α-sarcoglycan correction.

Tissue-Specific Regulation of CFTR Gene Expression.

More than 2000 variations are described within the CFTR (Cystic Fibrosis Transmembrane Regulator) gene and related to large clinical issues from cystic fibrosis to mono-organ diseases. Although these CFTR-associated diseases have been well documented, a large phenotype spectrum is observed and correlations between phenotypes and genotypes are still not well established. To address this issue, we present several regulatory elements that can modulate CFTR gene expression in a tissue-specific manner. Among them, cis-regulatory elements act through chromatin loopings and take part in three-dimensional structured organization. With tissue-specific transcription factors, they form chromatin modules and can regulate gene expression. Alterations of specific regulations can impact and modulate disease expressions. Understanding all those mechanisms highlights the need to expand research outside the gene to enhance our knowledge.

Research progress on ion channels and their molecular regulatory mechanisms in the human sperm flagellum.

The ion channels in sperm tail play an important role in triggering key physiological reactions, e.g., progressive motility, hyperactivation, required for successful fertilization. Among them, CatSper and KSper have been shown to be important ion channels for the transport of Ca2+ and K+ . Moreover, the voltage-gated proton channel Hv1, the sperm-specific sodium-hydrogen exchanger (sNHE), the epithelial sodium channel (ENaC), members of the temperature-sensitive TRP channel family, and the cystic fibrosis transmembrane regulator (CFTR) are also found in the flagellum. This review focuses on the latest advances in ion channels located at the flagellum, describes how they affect sperm physiological function, and summarizes some primary mutual regulation mechanism between ion channels, including PH, membrane potential, and cAMP. These ion channels may be promising targets for clinical application in infertility.

Loss of the Secretin Receptor Impairs Renal Bicarbonate Excretion and Aggravates Metabolic Alkalosis in Mice during Acute Base-Loading.

During acute base excess, the renal collecting duct β -intercalated cells ( β -ICs) become activated to increase urine base excretion. This process is dependent on pendrin and cystic fibrosis transmembrane regulator (CFTR) expressed in the apical membrane of β -ICs. The signal that leads to activation of this process was unknown. Plasma secretin levels increase during acute alkalosis, and the secretin receptor (SCTR) is functionally expressed in β -ICs. We find that mice with global knockout for the SCTR lose their ability to acutely increase renal base excretion. This forces the mice to lower their ventilation to cope with this challenge. Our findings suggest that secretin is a systemic bicarbonate-regulating hormone, likely being released from the small intestine during alkalosis. The secretin receptor (SCTR) is functionally expressed in the basolateral membrane of the β -intercalated cells of the kidney cortical collecting duct and stimulates urine alkalization by activating the β -intercalated cells. Interestingly, the plasma secretin level increases during acute metabolic alkalosis, but its role in systemic acid-base homeostasis was unclear. We hypothesized that the SCTR system is essential for renal base excretion during acute metabolic alkalosis. We conducted bladder catheterization experiments, metabolic cage studies, blood gas analysis, barometric respirometry, perfusion of isolated cortical collecting ducts, immunoblotting, and immunohistochemistry in SCTR wild-type and knockout (KO) mice. We also perfused isolated rat small intestines to study secretin release. In wild-type mice, secretin acutely increased urine pH and pendrin function in isolated perfused cortical collecting ducts. These effects were absent in KO mice, which also did not sufficiently increase renal base excretion during acute base loading. In line with these findings, KO mice developed prolonged metabolic alkalosis when exposed to acute oral or intraperitoneal base loading. Furthermore, KO mice exhibited transient but marked hypoventilation after acute base loading. In rats, increased blood alkalinity of the perfused upper small intestine increased venous secretin release. Our results suggest that loss of SCTR impairs the appropriate increase of renal base excretion during acute base loading and that SCTR is necessary for acute correction of metabolic alkalosis. In addition, our findings suggest that blood alkalinity increases secretin release from the small intestine and that secretin action is critical for bicarbonate homeostasis.

P222 Multi-central profile of refugee cystic fibrosis patients in Turkey

Cystic fibrosis (CF) is an autosomal recessive disease caused by cystic fibrosis transmembrane regulator protein (CFTR) gene mutations. The incidence of CF varies considerably among different ethnic groups worldwide, although it is most common in the Caucasian race. This study aims to examine the clinical course and treatment of CF among refugee patients in our country.