The Effects of Diet Intervention on the Gut Microbiota in Type 2 Diabetes Mellitus: A Systematic Review.

The GI tract hosts a dynamic community known as the gut microbiota, which encompasses thriving bacteria that actively contribute to the physiological functions of the human body. The intricacies of its composition are profoundly influenced by dietary preferences, where the quality, quantity, and frequency of food consumption play a pivotal role in either fostering or impeding specific bacterial strains. Type 2 diabetes mellitus (T2DM) is a prevalent and deleterious condition that originates from excessive hyperglycemia. Do lifestyle interventions targeting dietary adjustments, nutritional supplements, physical activity, and weight management programs exhibit a significant relationship in altering the composition of the gut microbiome and managing T2DM? This paper aims to evaluate the effects of lifestyle interventions on patients with T2DM and the implications of these changes on disease outcomes and progression. Lifestyle interventions can significantly impact the management of T2DM, especially those targeting dietary adjustments, nutritional supplements, physical activity, and weight management programs. The adoption of a high-fiber diet and increased fruit consumption have shown positive impacts on both insulin sensitivity and the composition of the gut microbiota. Additionally, promising outcomes emerge from supplementing with Omega-3 fatty acids, Vitamin K2 (MK-7), and transglucosidase, which influence insulin levels, glycemic control, and gut microbiota composition. Personalized diet interventions and the transformative effects of the Mediterranean diet present positive outcomes in metabolic control. The intensity of exercise plays a pivotal role in shaping the composition of the gut microbiota, with moderate-intensity continuous exercise displaying positive effects on anti-inflammatory microbes. Chronic exercise showcases favorable impacts on glycemic control and systemic inflammation. Emphasizing the intricate relationship between dietary habits, gut microbiota, and the risk of T2DM underscores the potential of the gut microbiota as a universal biomarker for assessing diabetes risk. Nutritional supplements and exercise interventions provide potential avenues for the management of T2DM, emphasizing the necessity for tailored strategies. Further research is encouraged to delve into the long-term effects and intricate interplay between lifestyle factors and the gut microbiome, enhancing our understanding of T2DM pathophysiology for targeted therapeutic approaches.

The Use of Psychotherapy for Refractory Irritable Bowel Syndrome: A Systematic Review.

Irritable bowel syndrome (IBS) is a common yet debilitating and chronic condition that consists of disturbances in bowel habits and abdominal pain that is frequently relieved with defecation. While the first line of treatment for IBS is pharmacological treatment, this has been shown to fail, leading to the patient being classified as having refractory IBS. The quality of life (QOL) of these patients is greatly hindered; in this case, there are rarely moments of relief. Additional modalities of treatment have been employed in classical cases of IBS, such as psychotherapy, and research has started to evaluate its effectiveness with refractory IBS. Both cognitive behavioral therapy (CBT) and gut-directed hypnotherapy (GDH) are effective in treating classical IBS as they restructure and bring a state of meditation to the patient, allowing them to work through the symptoms. The question is whether it remains successful in refractory cases. This systematic review was conducted with strict adherence to PRISMA guidelines with an initial inquiry resulting in 28,978 publications through PubMed, ScienceDirect, and ProQuest databases. Through automatic and manual screening processes, articles that were peer-reviewed experimental or observation publications done between 2003 and 2023 were included in this study, resulting in 21 publications. Across all studies evaluating CBT, it was consistently found to be successful in improving symptom severity and frequency, QOL, and extracolonic symptoms such as anxiety and depression. When broken down into delivery methods, minimal contact CBT was found to be just as, if not superior, to standard contact. Within this, telephone-delivered CBT was superior to web-delivered CBT. GDH and biofeedback therapy were found to also significantly improve all domains of IBS with no difference between them. Acceptance and commitment therapy were found only to improve associated symptoms. However, there was no significant improvement in their QOL, whereas integrative group therapy found no significant improvement in any domain. Because IBS is so common and crippling to those affected, its crucial to continuously improve QOL through advancement in treatment modalities. Further research should focus more on other modes of therapy as success has been shown in standard therapeutic techniques.

The Relationship Between Gestational Diabetes and the Risk of Cancer: A Systematic Review.

Gestational diabetes mellitus (GDM) is one of the most common endocrine disorders to occur during pregnancy due to the increase in circulating human placental lactogen (hPL) and possible beta-cell sensitivity. While GDM can be managed either with diet and exercise or pharmacological interventions, it is associated with significant maternal and neonatal complications. Maternal complications include short- and long-term conditions such as pre-eclampsia, preterm birth, arrest of labor, future development of type 2 diabetes mellitus (T2DM), and cardiovascular disorders. Neonates can develop hypoglycemia and hypocalcemia and have a large gestational age (LGA). New research has also highlighted another possible long-term complication for both mothers and offspring, which is the development of cancer. Cancer has various types of progression, but most cause systemic symptoms leading to a reduced quality of life. Cancer can be terminal and can affect the majority of the population; thus, significant effort is being employed to try and reduce its occurrence. This systematic review was conducted with adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using PubMed, ScienceDirect, and ProQuest databases. Initially, 136,019 publications were identified. Through the screening process, a total of 27 publications were finalized within the scope of this paper. Most studies observing maternal cancer with a history of GDM found that there was an association between the increased risk of cancer and GDM. Specifically, these studies identified the association of GDM with breast, ovarian, cervical, and uterine cancer, as well as other non-reproductive organs such as the thyroid and pancreas. Cancer development in the offspring also presented an association with mothers who developed GDM. The most prevalent cancer evaluated was leukemia, and it was specifically associated with a maternal history of GDM. With the consistent rise in the incidence of cancer, any attempts to reduce its development are imperative to assess. While GDM is essentially a temporary condition that resolves following pregnancy in most patients, the possibility of contributing to future conditions years after its occurrence creates a sense of urgency and necessity to reduce the incidence of GDM. Researchers should be able to identify other unknown biomarkers that contribute to the development of cancer in mothers who experienced GDM as well as their infants.

Botulinum Toxin for the Management of Parkinson's Disease: A Systematic Review.

Parkinson's disease (PD) is a terminal, debilitating neurodegenerative disorder typically affecting individuals over 60. It is associated with various conditions that drastically affect the patient's quality of life (QoL). Although there is no cure for PD, its symptoms can be significantly improved and even resolved through different treatments. Mainstay treatments for PD include levodopa combined with carbidopa, dopamine agonists, and even deep brain stimulation (DBS) of the subthalamic nucleus. New treatment methods have emerged, such as botulinum toxin (BoNT), which further improve symptoms and, thus, the QoL of patients with PD. Botulinum toxin is a potent neurotoxin produced by Clostridium botulinum that typically causes descending paralysis by suppressing acetylcholine secretion. Serotypes used to treat various disorders include serotype A (BoNT-A) and serotype B (BoNT-B). This paper aims to evaluate the outcomes of BoNT injection on different symptoms associated with PD. An extensive review using PubMed, ScienceDirect, and ProQuest articles concerning 'botulinum toxin and Parkinson's disease' was done per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, resulting in 23,803 articles. After applying strict inclusion and exclusion criteria, the total number of articles was finally 41. The results showed that movement disorders were a common occurrence in PD, consisting of tremors, dystonia, and freezing of gait (FOG), with tremors being the most common symptom. Tremors and dystonia were significantly improved following BoNT-A, correlating with significant improvements in various scales subjectively and objectively evaluating the symptoms and QoL. In contrast, FOG was not significantly improved by either BoNT-A or BoNT-B. Pain is associated with movement disorders such as PD and was the primary indication for the administration of BoNT; studies found pain and QoL were significantly improved following BoNT injection. Quality of life can also be affected by sialorrhea and overactive bladder, which often occur as the disease progresses. Injections of BoNT-A and BoNT-B were shown to significantly improve saliva production, flow rate, drooling frequency, voiding frequency, and urinary urge incontinence. Across all studies analyzed, it is evident that BoNT may have a significant effect on improving the QoL of patients suffering from PD. While research continues to find a cure or stop the progression of PD, it remains critical to continue focusing on improving patients' QoL. Future research should evaluate whether BoNT can be used to successfully treat other symptoms of PD, such as epiphora or constipation.

Transvaginal Laparoscopic Appendectomy: A Systematic Review.

Appendectomy remains the gold standard for treating appendicitis, but advancements in laparoscopic techniques have shifted the paradigm. Natural orifice transluminal endoscopic surgery (NOTES) and transvaginal appendectomy (TVA) offer a potentially less invasive alternative to traditional laparoscopic appendectomy (LA). This article systematically reviews the procedures, perceptions, and complications of TVA to assess its viability as a surgical option. Between January 1, 2003, and November 1, 2023, 4832 case reports, case series, and experimental and observational peer-reviewed publications were examined and filtered using the keyword "Transvaginal Laparoscopic Appendectomy." The publications were screened using PRISMA guidelines, and 20 studies were included for analysis and review. Survey results showed that women's acceptance of TVA was 43%, citing reduced invasiveness as a major reason for positive reception. TVA procedures exhibited consistency, with variations in appendectomy methods, appendix removal, and posterior fornix incision closure. Positive outcomes included shorter operation times, reduced postoperative pain, and minimal scarring. Complications were uncommon but included bladder puncture, urinary tract infections, and intra-abdominal abscesses. Indications primarily focused on surgical safety, reduced scarring, and postoperative benefits. Sexual function post-TVA exhibited no significant differences in most cases, with a recovery period of two to four weeks. This systematic review suggests that TVA is a promising alternative to traditional LA, offering potential advantages in terms of postoperative complications. While the existing literature indicates positive outcomes, further research with larger sample sizes and long-term follow-ups is needed to validate the efficacy and safety of TVA and assess how the procedure impacts the reproductive function of patients.

Pain Management During Adult Laparoscopic Appendectomy: A Systematic Review.

The opioid epidemic has become a critical public health issue, driven by the widespread distribution and misuse of prescription opioids. This paper investigates analgesic management in the context of laparoscopic appendectomy (LA) as an alternative to open appendectomy, aiming to reduce the reliance on opioids for postoperative pain control. A comprehensive literature review was conducted from January 1, 2003, to November 1, 2023, utilizing PubMed, ProQuest, and ScienceDirect databases. The search focused on peer-reviewed experimental and observational studies involving adults (18 years and older) undergoing LA. The original search resulted in 18,258 publications, which were then screened using PRISMA guidelines. Among the filtered 18 studies included for analysis and review, the transition from open to LA demonstrated a consistent decrease in postoperative pain, leading to a reduced need for opioid prescriptions. Analgesic strategies included the use of local anesthetics (lidocaine, bupivacaine, ropivacaine), spinal/epidural anesthesia, nerve blocks, and a multimodal approach with NSAIDs and acetaminophen. Studies demonstrated the efficacy of local anesthetics in reducing postoperative pain, prompting a shift toward non-opioid analgesics. The use of spinal/epidural anesthesia and nerve blocks further supported the trend of minimizing opioid prescriptions. While some variations in anesthetic approaches existed, overall, patients undergoing LA required fewer opioid doses, reflecting a positive shift in postoperative pain management. Patients undergoing LA experienced lower rates of readmission, reduced post-operative pain, better cosmetic outcomes, and shorter recovery times, contributing to a diminished demand for opioid medications. This review underscores the potential for non-opioid analgesic strategies in surgical contexts, aligning with the broader imperative to address the opioid epidemic and promote safer and more sustainable pain management practices.

Infective Endocarditis Following Aortic Valve Replacement: A Systematic Review.

Aortic valve replacement (AVR) successfully treats aortic valve stenosis and aortic regurgitation from aging or bicuspid aortic valves. The procedure intends to restore the obstructed left ventricular outflow tract (LVOT). AVR can be performed surgically (surgical aortic valve replacement (SAVR); open heart) or via transcatheter (transcatheter aortic valve replacement (TAVR)), typically done through a femoral approach as a minimally invasive procedure, allowing for quicker recovery and reduced hospital stays. AVR has many complications, including life-threatening ones, such as infective endocarditis (IE), retarding the recovery process and increasing mortality following surgery. IE is an uncommon and deadly condition that involves multiple organ systems and is caused by bacteremia stemming from a microorganism that enters the bloodstream. Many manifestations are involved in the development of IE, such as fevers, flu-like symptoms, splinter hemorrhages, Osler nodes, abscesses, and vegetations found on the valves at the leaflets. Vegetations and abscesses tend to create further complications, such as stroke and acute kidney injury, as emboli block blood flow, leading to ischemia and damage. This paper aims to evaluate the difference in SAVR- and TAVR-associated IE, as the goal is to elucidate a danger that diminishes the positive effects of either procedure despite its rarity. Studies have been inconclusive in determining whether or not there is a trend, let alone a difference in incident rates. Both procedures share similar risk factors, but SAVR-associated IE is usually caused by Staphylococcus aureus, and studies indicate possibly Enterococcus spp. in TAVR-associated IE. Incident rates of IE are much higher than they should be, whether or not they differ between procedures, and future research needs to consider the pathways and risk factors that can be used to reduce the occurrence of AVR-associated IE.

Anti-diabetics and the Prevention of Dementia: A Systematic Review.

Type 2 diabetes mellitus (T2DM) is a worldwide epidemic that is only increasing as the years progress, and as of 2019, affecting over 37 million. T2DM is a chronic condition caused by reduced insulin secretion and increased insulin resistance. Due to insulin not operating at optimal conditions, blood glucose rises and remains high, thus disturbing metabolic hemostasis. Many complications can arise from T2DM, such as coronary vascular disease, kidney damage, eye damage, and, quite significantly, dementia. It is theorized that dementia from T2DM stems from the fact that the brain is susceptible to hyperglycemic conditions, which are promoted by the increase in insulin resistance of target cells in the central nervous system. This directly affects cognitive processes and memory, which correlates to decreased temporal and front lobes volume. The risk of diabetic complications can be minimized with therapeutic interventions such as oral-antidiabetic (OAD) agents and insulin. Several OADs are on the market, but the first-line agent is metformin, a biguanide that decreases glucose production and increases insulin sensitivity. This paper aims to determine if currently prescribed OADs can help slow cognitive decline and reduce the risk and incidence of dementia as a complication of T2DM. Studies found that, for the most part, all OADs except sulfonylureas (SU) significantly slowed the decline of cognitive function and reduced the risk and incidence of dementia. SU's were shown to increase the risk of dementia in most studies. Of all the OADs, thiazolidinediones may be the most beneficial drug class for reducing the risk of dementia in T2DM patients. Future research should focus on whether early intervention with specific classes of OADs can not only improve glycemic control, leading to decreased hyperglycemia but also prevent the build-up of damaged brain tissue and help to reduce the risk and incidence of dementia in patients with T2DM.

Risk of Infective Endocarditis Post-transcatheter Pulmonary Valve Replacement Versus Surgical Pulmonary Valve Replacement: A Systematic Review.

Pulmonary valve replacement (PVR) is the most common cardiac operation in adult patients with congenital heart disease (ACHD). It can improve right ventricular outflow tract (RVOT) obstruction, typically due to pulmonary valve stenosis or regurgitation. PVR can be performed surgically (open-heart) and through a transcatheter (percutaneous) method, which is minimally invasive and is associated with shorter hospitalization stays. However, following PVR, infectious endocarditis (IE) can complicate the recovery process and increase mortality in the long term. IE is a rare but deadly multi-organ system condition caused by microorganisms traversing the bloodstream from a specific entry point. It can have many presentations, such as splinter hemorrhages, fevers, and vegetation on valves that lead to stroke consequences. This paper aims to evaluate the differences in the rate, etiology, manifestations, treatment, and outcomes of IE following surgical and transcatheter PVR, as the goal is to perform a procedure with few complications. In both approaches, Staphylococcus aureus was the most common microorganism that affected the valves, followed by Streptococcus viridians. Research has shown that surgical pulmonary valve replacement (SPVR) has a decreased risk of IE following surgery compared to TPVR. However, TPVR is preferred due to the reduced overall risk and complications of the procedure. Despite this, the consensus on mortality rates does differ. Future research should consider the type of valves used for transcatheter pulmonary valve replacement (TPVR), such as Melody valves versus Edward Sapien valves, as their IE rates vary significantly.

Gestational Diabetes Mellitus in the Setting of Polycystic Ovarian Syndrome: A Systematic Review.

Gestational diabetes mellitus (GDM) is the most common complication of pregnancy that arises in the 2nd and 3rd trimesters, leading to significant complications for the mother and her neonates, such as an increased rate of pregnancy-induced hypertension and miscarriages, while neonates may have a large birth weight, hypoglycemia, or macrosomnia. Numerous risk factors can lead to GDM; however, a significant one is polycystic ovarian syndrome (PCOS). PCOS is the most common endocrine pathology beginning before puberty, and due to significant hormonal changes, it is not diagnosed until after puberty. PCOS requires at least three of the following symptoms: hyperandrogenism, menstrual irregularities, or polycystic ovary morphology. While it is agreed that women with PCOS are at a significantly increased risk of GDM, no publication to our knowledge has evaluated the full relationship of GDM in the setting of PCOS. This paper aimed to assess this relationship and determine how it may differ for pregnant women with only GDM by determining the prevalence of GDM, the variations within phenotypes, the influence of fertilization methods, specific risk factors, maternal outcomes, and neonatal outcomes. The prevalence of GDM was significantly increased in women with PCOS compared to healthy controls, and some studies have found that phenotype A may be more likely to lead to GDM. Risk factors were similar to pregnant women with only GDM, but with GDM and PCOS specifically, preconception low sex hormone-binding globulin, increased BMI > 25 kg/m2, and preconception impaired glucose tolerance were specific. While maternal outcomes were similar to pregnant women with only GDM, women with GDM and PCOS were even more likely to develop pregnancy-induced hypertension and early miscarriage. Neonates from mothers with GDM and PCOS were more likely to have low birth weights compared to mothers with just GDM who had high birth weights. The evaluation of the relationship between GDM and PCOS allows for illumination of the need to evaluate influences that currently lack research, such as phenotype variation and influences of fertilization method. This also promotes the need to develop predictive algorithms based on risk factors to prevent these adverse outcomes for mothers and neonates.

Psychotherapy for Irritable Bowel Syndrome: A Systematic Review.

Psychotherapy has many forms, such as cognitive behavioral therapy (CBT), mindfulness therapy (MFT), and hypnotherapy, to name a few. Cognitive behavioral therapy is the gold standard in therapy-based treatment and is used for cognitive restructuring to reduce safety-seeking and avoidant behaviors. While the main application of psychotherapy is psychological disorders, recent studies have found that it is beneficial for somatic and physiological symptoms such as chronic pain or even irritable bowel syndrome (IBS). Irritable bowel syndrome is a common but debilitating gastrointestinal condition that has a prevalence of 12% in the United States and costs the average patient $9,776 annually in 2023. Irritatable bowel syndrome is a condition of exclusion but consists of abdominal discomfort or pain and must be associated with altered bowel habits as stated in the Rome IV criteria. At least half of these patients also exhibit extracolonic symptoms, most commonly psychological disorders like anxiety and stress. The true etiology of IBS is not understood, but ideas such as the brain-gut axis, stress response system, and gut microbiota have been evaluated. Treatment of IBS is extensive and heavily relies on the patient-physician interaction, but pharmacologic therapies have been employed and are sometimes unsuccessful. Irritable bowel syndrome impacts an individual as a whole, making them hesitate whether or not they eat a particular food or even go out to do an activity because of the unpredictable bowel pattern. Finding a better solution is essential to improving the patient's quality of life (QoL), especially by addressing how they perceive the illness, how they adjust to it, and even how they determine what foods to consume. This paper aims to evaluate whether or not psychotherapy can be employed to improve all aspects of IBS, as well as if it can reduce the cost of IBS treatment.

Sex Differences in Infective Endocarditis: A Systematic Review.

Despite the advancement in medicine, there is still a lack of understanding of the sex disparities in disease onset, progression, treatment, and outcome. In some life-threatening acute conditions, despite most patients with these illnesses being males, females have a significantly higher chance of mortality. This can be due to the differences in disease progression or healthcare disparities in managing the illness between the sexes. Treatment of illnesses tends to be more conservative for women without an explanation, but this disparity is due to the healthcare provider. Infective endocarditis (IE) is an acute life-threatening condition where bacteria latch onto and seed damaged endocardium, with some preliminary information reporting differences between the sexes. This paper aims to evaluate the sex disparities in the incidence, age, comorbidities, etiology, risk factors, manifestations, treatment, and outcomes of IE. From 2003-2023, 21584 articles were found that focused on the sex differences in IE and, through PRISMA guidelines, were narrowed down to 34 publications. There are significant differences between the sexes in IE, such as a significantly higher incidence of IE in males, who also tend to be older and have their native aortic valves involved, compared to younger females who have their mitral valve involved. Comorbidities also vary between the sexes; females tend to have atrial fibrillation, chronic kidney disease, psychiatric disorders, and taking immunosuppressants compared to males who suffer from chronic liver disease, underlying valve disease, and peripheral artery disease, contributing to the ease of developing IE. While the most common microorganism leading to IE is Staphylococcus aureus, females were more likely to have culture-negative IE, and men were more likely to be infected with Streptococcus viridans. Major manifestations in IE are fever and vegetation along the closure of the valves in the heart, where females were more likely to have vegetation on the mitral and aortic valves. At the same time, males were more likely to have it on the tricuspid valve. On par with sex disparities in health, females usually took longer to seek medical help than males despite the advancement of symptoms and deterioration. Females were also treated conservatively through antibiotic management, whereas males were more likely to advance to surgical treatment, leading to a longer hospital stay. While there was no true difference in the in-hospital mortality rate, the 30-day and 1-year mortality were significantly increased in females. These differences provide a range of starting points for various research to further educate physicians on sex disparities, such as why males have a higher incidence of infective endocarditis and determining whether it's hormones and basic metabolites, possibly limiting those who develop the infection. Another important point is treating females with IE; the antibiotic doses are standard, but whether they advance to surgical treatment is mostly up to the provider. Some providers deny surgical treatment despite all indications, but it could also be females denying surgery as they tend to leave against medical advice. This review is crucial in developing the next steps to sex disparity in IE, which may lead to better outcomes for males and females.

Type-2 Diabetes Mellitus and the Gut Microbiota: Systematic Review.

The gut microbiota is a community situated in the gastrointestinal tract that consists of bacteria thriving and contributing to the functions of our body. It is heavily influenced by what individuals eat, as the quality, amount, and frequency of food consumed can favor and inhibit specific bacteria. Type-2 diabetes mellitus (T2DM) is a common but detrimental condition that arises from excessive hyperglycemia, leading to either insulin resistance or damage to the B-cells that produce insulin in the pancreas. A poor diet high in sugar and fats leads to hyperglycemia, and as this persists, it can lead to the development of T2DM. Both insulin resistance and damage to B-cells are greatly affected by the diet an individual consumes, but is there a more involved relationship between the gut microbiota and T2DM? This paper aimed to evaluate the changes in the gut microbiota in patients with T2DM and the impacts of the changes in gut microbiota. Bacteroides, Proteobacteria, Firmicutes, and Actinobacteria prevailed in patients with T2DM and healthy control, but their abundance varied greatly. There was also a significant decrease in bacteria like Lactobacilli spp.and F. prausnitizii associated with insulin resistance. High levels of BMI in patients with T2DM have also been associated with increased levels of A. muciniphilia, which has been associated with decreased fat metabolism and increased BMI. Metabolites such as butyrates and melatonin have also been identified as influencing the development and progression of T2DM. Testosterone levels have also been greatly influenced by the gut microbiota changes in T2DM, such that males with lower testosterone have a greater abundance of bacteria like Gemella, Lachnospiraceae, and Massiia. Identifying these changes and how they impact the body may lead to a treatment addressing insulin dysfunction and the changes that the altered gut microbiota leads to. Future research should address how treatment methods such as healthy diets, exercise, and anti-diabetics affect the gut microbiota and see if they influence sustained changes and reduced hyperglycemia.

Epithelial vectorial ion transport in cystic fibrosis: Dysfunction, measurement, and pharmacotherapy to target the primary deficit.

Cystic fibrosis patients display multi-organ system dysfunction (e.g. pancreas, gastrointestinal tract, and lung) with pathogenesis linked to a failure of Cl- secretion from the epithelial surfaces of these organs. If unmanaged, organ dysfunction starts early and patients experience chronic respiratory infection with reduced lung function and a failure to thrive due to gastrointestinal malabsorption. Early mortality is typically caused by respiratory failure. In the past 40 years of newborn screening and improved disease management have driven the median survival up from the mid-teens to 43-53, with most of that improvement coming from earlier and more aggressive management of the symptoms. In the last decade, promising pharmacotherapies have been developed for the correction of the underlying epithelial dysfunction, namely, Cl- secretion. A new generation of systemic drugs target the mutated Cl- channels in cystic fibrosis patients and allow trafficking of the immature mutated protein to the cell membrane (correctors), restore function to the channel once in situ (potentiators), or increase protein levels in the cells (amplifiers). Restoration of channel function prior to symptom development has the potential to significantly change the trajectory of disease progression and their evidence suggests that a modest restoration of Cl- secretion may delay disease progression by decades. In this article, we review epithelial vectorial ion and fluid transport, its quantification and measurement as a marker for cystic fibrosis ion transport dysfunction, and highlight some of the recent therapies targeted at the dysfunctional ion transport of cystic fibrosis.

Molecular basis for pH-dependent mucosal dehydration in cystic fibrosis airways.

The ability to maintain proper airway surface liquid (ASL) volume homeostasis is vital for mucus hydration and clearance, which are essential aspects of the mammalian lung's innate defense system. In cystic fibrosis (CF), one of the most common life-threatening genetic disorders, ASL dehydration leads to mucus accumulation and chronic infection. In normal airways, the secreted protein short palate lung and nasal epithelial clone 1 (SPLUNC1) effectively inhibits epithelial Na(+) channel (ENaC)-dependent Na(+) absorption and preserves ASL volume. In CF airways, it has been hypothesized that increased ENaC-dependent Na(+) absorption contributes to ASL depletion, and hence increased disease. However, this theory is controversial, and the mechanism for abnormal ENaC regulation in CF airways has remained elusive. Here, we show that SPLUNC1 is a pH-sensitive regulator of ENaC and is unable to inhibit ENaC in the acidic CF airway environment. Alkalinization of CF airway cultures prevented CF ASL hyperabsorption, and this effect was abolished when SPLUNC1 was stably knocked down. Accordingly, we resolved the crystal structure of SPLUNC1 to 2.8 Å. Notably, this structure revealed two pH-sensitive salt bridges that, when removed, rendered SPLUNC1 pH-insensitive and able to regulate ASL volume in acidic ASL. Thus, we conclude that ENaC hyperactivity is secondary to reduced CF ASL pH. Together, these data provide molecular insights into the mucosal dehydration associated with a range of pulmonary diseases, including CF, and suggest that future therapy be directed toward alkalinizing the pH of CF airways.

Cigarette smoke exposure induces CFTR internalization and insolubility, leading to airway surface liquid dehydration.

Cigarette smoke (CS) exposure induces mucus obstruction and the development of chronic bronchitis (CB). While many of these responses are determined genetically, little is known about the effects CS can exert on pulmonary epithelia at the protein level. We, therefore, tested the hypothesis that CS exerts direct effects on the CFTR protein, which could impair airway hydration, leading to the mucus stasis characteristic of both cystic fibrosis and CB. In vivo and in vitro studies demonstrated that CS rapidly decreased CFTR activity, leading to airway surface liquid (ASL) volume depletion (i.e., dehydration). Further studies revealed that CS induced internalization of CFTR. Surprisingly, CS-internalized CFTR did not colocalize with lysosomal proteins. Instead, the bulk of CFTR shifted to a detergent-resistant fraction within the cell and colocalized with the intermediate filament vimentin, suggesting that CS induced CFTR movement into an aggresome-like, perinuclear compartment. To test whether airway dehydration could be reversed, we used hypertonic saline (HS) as an osmolyte to rehydrate ASL. HS restored ASL height in CS-exposed, dehydrated airway cultures. Similarly, inhaled HS restored mucus transport and increased clearance in patients with CB. Thus, we propose that CS exposure rapidly impairs CFTR function by internalizing CFTR, leading to ASL dehydration, which promotes mucus stasis and a failure of mucus clearance, leaving smokers at risk for developing CB. Furthermore, our data suggest that strategies to rehydrate airway surfaces may provide a novel form of therapy for patients with CB.

Defective adenosine-stimulated cAMP production in cystic fibrosis airway epithelia: a novel role for CFTR in cell signaling.

Adenosine (ADO) is an extracellular signaling molecule that is an important regulator of innate lung defense. On binding ADO, the A2B receptor (A2BR) stimulates cAMP production to activate the CFTR Cl(-) channel, increase ciliary beating, and initiate cytokine secretion. We tested the hypothesis that CFTR served as a positive regulator of the A2BRs. We found that A2BR and CFTR coimmunoprecipitated. They also underwent ADO-dependent Förster resonance energy transfer (FRET), which increased from 5% in the absence of agonist to 18% with 100 µM ADO (EC50 1.7 µM), suggesting that they dynamically associate in the plasma membrane. In contrast, despite colocalization, no FRET was observed between CFTR and GAP43. The interaction between A2BR and CFTR had some specificity: A2BR-stimulated but not forskolin-stimulated cAMP production was ~50% greater in the presence of CFTR, due to a CFTR-dependent increase in plasma membrane A2BR levels. These CFTR-dependent increases in A2BR levels and cAMP production resulted in significantly enhanced ciliary beating and increased cytokine secretion in normal compared to cystic fibrosis airway epithelia. Thus, we hypothesize that CFTR regulates A2BR levels in the plasma membrane to modulate cell signaling and to enhance selective components of the innate lung defense system.

Nucleotide-mediated airway clearance.

A thin layer of airway surface liquid (ASL) lines the entire surface of the lung and is the first point of contact between the lung and the environment. Surfactants contained within this layer are secreted in the alveolar region and are required to maintain a low surface tension and to prevent alveolar collapse. Mucins are secreted into the ASL throughout the respiratory tract and serve to intercept inhaled pathogens, allergens and toxins. Their removal by mucociliary clearance (MCC) is facilitated by cilia beating and hydration of the ASL by active ion transport. Throughout the lung, secretion, ion transport and cilia beating are under purinergic control. Pulmonary epithelia release ATP into the ASL which acts in an autocrine fashion on P2Y(2) (ATP) receptors. The enzymatic network describes in Chap. 2 then mounts a secondary wave of signaling by surface conversion of ATP into adenosine (ADO), which induces A(2B) (ADO) receptor-mediated responses. This chapter offers a comprehensive description of MCC and the extensive ramifications of the purinergic signaling network on pulmonary surfaces.

17beta-Estradiol inhibits Ca2+-dependent homeostasis of airway surface liquid volume in human cystic fibrosis airway epithelia.

Normal airways homeostatically regulate the volume of airway surface liquid (ASL) through both cAMP- and Ca2+-dependent regulation of ion and water transport. In cystic fibrosis (CF), a genetic defect causes a lack of cAMP-regulated CFTR activity, leading to diminished Cl- and water secretion from airway epithelial cells and subsequent mucus plugging, which serves as the focus for infections. Females with CF exhibit reduced survival compared with males with CF, although the mechanisms underlying this sex-related disadvantage are unknown. Despite the lack of CFTR, CF airways retain a limited capability to regulate ASL volume, as breathing-induced ATP release activates salvage purinergic pathways that raise intracellular Ca2+ concentration to stimulate an alternate pathway to Cl- secretion. We hypothesized that estrogen might affect this pathway by reducing the ability of airway epithelia to respond appropriately to nucleotides. We found that uridine triphosphate-mediated (UTP-mediated) Cl- secretion was reduced during the periovulatory estrogen maxima in both women with CF and normal, healthy women. Estrogen also inhibited Ca2+ signaling and ASL volume homeostasis in non-CF and CF airway epithelia by attenuating Ca2+ influx. This inhibition of Ca2+ signaling was prevented and even potentiated by estrogen antagonists such as tamoxifen, suggesting that antiestrogens may be beneficial in the treatment of CF lung disease because they increase Cl- secretion in the airways.

In vivo versus in vitro airway surface liquid nicotine levels following cigarette smoke exposure.

Whole cigarette smoke (WCS) is composed of approximately 5% particulates and 95% vapors by weight and is difficult to reproduce quantitatively in the laboratory, where typically, routine in vitro application of smoke normally only utilizes the particulate phase. In this study, we used a system for exposing epithelial cells cultured at an air-liquid interface to WCS. We hypothesized that the use of WSC in vitro was more relevant to what is seen in vivo than methods of cigarette smoke application that only use a small fraction of WCS [i.e., aqueous extract or cigarette smoke condensate (CSC)]. To test this hypothesis, we compared nicotine and cotinine concentrations (measured by mass spectrometry) in the airway surface liquid (ASL) of human primary bronchial epithelial cultures (HBECs) exposed to serial dilutions of WCS to the concentrations found in induced sputum of human subjects who had recently smoked a cigarette; this was also compared to the concentrations found after an exposure to a concentration of CSC commonly used in vitro. When measured by mass spectrometry, nicotine levels were not significantly different in induced sputum versus the ASL of HBECs exposed in vitro to a 1:30 exposure of WCS. However, HBECs that had been exposed to CSC returned significantly lower concentrations of ASL nicotine. These results suggest that nicotine is a good dosimetry marker of WCS exposure and provides direct evidence that the use of WCS is more relevant than the use of CSC for in vitro systems.