Potentiation of the effect of thiazide derivatives by carbonic anhydrase inhibitors: molecular mechanisms and potential clinical implications

Acetazolamide therapy in patients with acute heart failure: a systematic review and meta-analysis of randomized controlled trials

Acute heart failure (AHF) often leads to unfavorable outcomes due to fluid overload. While diuretics are the cornerstone treatment, acetazolamide may enhance diuretic efficiency by reducing sodium reabsorption. We performed a systematic review and meta-analysis on the effects of acetazolamide as an add-on therapy in patients with AHF compared to diuretic therapy. PubMed, Embase, and Cochrane databases were searched for randomized controlled trials (RCT). A random-effects model was employed to compute mean differences and risk ratios. Statistical analysis was performed using R software. The GRADE approach was used to rate the certainty of the evidence. We included 4 RCTs with 634 patients aged 68 to 81 years. Over a mean follow-up of 3 days to 34 months, acetazolamide significantly increased diuresis (MD 899.2 mL; 95% CI 249.5 to 1549; p < 0.01) and natriuresis (MD 72.44 mmol/L; 95% CI 39.4 to 105.4; p < 0.01) after 48 h of its administration. No association was found between acetazolamide use and WRF (RR 2.4; 95% CI 0.4 to 14.2; p = 0.3) or all-cause mortality (RR 1.2; 95% CI 0.8 to 1.9; p = 0.3). Clinical decongestion was significantly higher in the intervention group (RR 1.35; 95% CI 1.09 to 1.68; p = 0.01). Acetazolamide is an effective add-on therapy in patients with AHF, increasing diuresis, natriuresis, and clinical decongestion, but it was not associated with differences in mortality.

Acetazolamide as an Adjunctive Diuretic Therapy for Patients with Acute Decompensated Heart Failure: A Systematic Review and Meta-Analysis

BACKGROUND

Recent evidence suggests that acetazolamide may be beneficial as an adjunctive diuretic therapy in patients with acute decompensated heart failure (HF). We aim to pool all the studies conducted until now and provide updated evidence regarding the role of acetazolamide as adjunctive diuretic in patients with acute decompensated HF.

METHODS

PubMed/Medline, Cochrane Library, and Scopus were searched from inception until July 2023, for randomized and nonrandomized studies evaluating acetazolamide as add-on diuretic in patients with acute decompensated HF. Data about natriuresis, urine output, decongestion, and the clinical signs of congestion were extracted, pooled, and analyzed. Data were pooled using a random effects model. Results were presented as risk ratios (RRs), odds ratios (ORs), or weighted mean differences (WMD) with 95% confidence intervals (95% CIs). Certainty of evidence was assessed using the grading of recommendation, assessment, development, and evaluation (GRADE) approach. A P value of < 0.05 was considered significant in all cases.

RESULTS

A total of 5 studies (n = 684 patients) were included with a median follow-up time of 3 months. Pooled analysis demonstrated significantly increased natriuresis (MD 55.07, 95% CI 35.1-77.04, P < 0.00001; I2 = 54%; moderate certainty), urine output (MD 1.04, 95% CI 0.10-1.97, P = 0.03; I2 = 79%; moderate certainty) and decongestion [odds ratio (OR) 1.62, 95% CI 1.14-2.31, P = 0.007; I2 = 0%; high certainty] in the acetazolamide group, as compared with controls. There was no significant difference in ascites (RR 0.56, 95% CI 0.23-1.36, P = 0.20; I2 = 0%; low certainty), edema (RR 1.02, 95% CI 0.52-2.0, P = 0.95; I2 = 45%; very low certainty), raised jugular venous pressure (JVP) (RR 0.86, 95% CI 0.63-1.17, P = 0.35; I2 = 0%; low certainty), and pulmonary rales (RR 0.82, 95% CI 0.44-1.51, P = 0.52; I2 = 25%; low certainty) between the two groups.

CONCLUSIONS

Acetazolamide as an adjunctive diuretic significantly improves global surrogate endpoints for decongestion therapy but not all individual signs and symptoms of volume overload.

SYSTEMATIC REVIEW REGISTRATION

This systematic review was prospectively registered on the PROSPERO ( https://www.crd.york.ac.uk/PROSPERO/ ), registration number CRD498330.

Contemporary Decongestive Strategies in Acute Heart Failure

Congestion is the primary driver of hospital admissions in patients with heart failure and the key determinant of their outcome. Although intravenous loop diuretics remain the predominant agents used in the setting of acute heart failure, the therapeutic response is known to be variable, with a significant subset of patients discharged from the hospital with residual hypervolemia. In this context, urinary sodium excretion has gained attention both as a marker of response to loop diuretics and as a marker of prognosis that may be a useful clinical tool to guide therapy. Several decongestive strategies have been explored to improve diuretic responsiveness and removal of excess fluid. Sequential nephron blockade through combination diuretic therapy is one of the most used methods to enhance natriuresis and counter diuretic resistance. In this article, I provide an overview of the contemporary decongestive approaches and discuss the clinical data on the use of add-on diuretic therapy. I also discuss mechanical removal of excess fluid through extracorporeal ultrafiltration with a brief review of the results of landmark studies. Finally, I provide a short overview of the strategies that are currently under investigation and may prove helpful in this setting.

Combination Diuretic Therapy to Counter Renal Sodium Avidity in Acute Heart Failure: Trials and Tribulations

In contrast to significant advances in the management of patients with chronic heart failure over the past few years, there has been little change in how patients with acute heart failure are treated. Symptoms and signs of fluid overload are the primary reason for hospitalization of patients who experience acute decompensation of heart failure. Intravenous loop diuretics remain the mainstay of therapy in this patient population, with a significant subset of them showing suboptimal response to these agents leading to incomplete decongestion at the time of discharge. Combination diuretic therapy, that is, using loop diuretics along with an add-on agent, is a widely applied strategy to counter renal sodium avidity through sequential blockade of sodium absorption within renal tubules. The choice of the second diuretic is affected by several factors, including the site of action, the anticipated secondary effects, and the available evidence on their efficacy and safety. While the current guidelines recommend combination diuretic therapy as a viable option to overcome suboptimal response to loop diuretics, it is also acknowledged that this strategy is not supported by strong evidence and remains an area of uncertainty. The recent publication of landmark studies has regenerated the interest in sequential nephron blockade. In this article, we provide an overview of the results of the key studies on combination diuretic therapy in the setting of acute heart failure and discuss their findings primarily with regard to the effect on renal sodium avidity and cardiorenal outcomes.

Effect of Acetazolamide as Add-On Diuretic Therapy in Patients With Heart Failure: A Meta-Analysis

The aim of this meta-analysis was to assess the effectiveness of acetazolamide as an add-on diuretic therapy in patients with heart failure. This meta-analysis was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. A systematic literature search was independently performed by two authors using MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews to identify relevant studies assessing the use of acetazolamide in patients with heart failure. The search keywords included "acetazolamide" and "heart failure". The outcomes assessed in this meta-analysis included natriuresis (mmol/L), diuresis (Liters) and decongestion (absence of signs of volume overload) by 72 hours. Other outcomes assessed in this meta-analysis included hospitalization due to heart failure and all-cause mortality. A total of three studies included a total of 569 heart failure patients. The number of patients achieved decongestion was significantly higher in patients receiving acetazolamide compared to the patients randomized in the control group (RR: 1.34, 95% CI: 1.06-1.67). Compared to patients in the control group, mean natriuresis was significantly higher in acetazolamide patients (MD: 74.91, 95% CI: 39.85-109.97). Diuresis was significantly higher in patients receiving acetazolamide compared to the control group (MD: 0.44, 95% CI: 0.16-0.72). No significant difference was found between the two groups in terms of all-cause mortality and hospitalization due to heart failure. In conclusion, our meta-analysis suggests that acetazolamide may have beneficial impacts on heart failure patients by increasing the number of successful decongestions. Additionally, patients who were treated with acetazolamide had significantly higher natriuresis and diuresis compared to patients in the control group.

Serum Chloride and Heart Failure

Despite significant advances in management, heart failure continues to impose a significant epidemiologic burden with high prevalence and mortality rates. For decades, sodium has been the serum electrolyte most commonly associated with outcomes; however, challenging the conventional paradigm of sodium's influence, recent studies have identified a more prominent role in serum chloride in the pathophysiology of heart failure. More specifically, hypochloremia is associated with neurohumoral activation, diuretic resistance, and a worse prognosis in patients with heart failure. This review examines basic science, translational research, and clinical studies to better characterize the role of chloride in patients with heart failure and additionally discusses potential new therapies targeting chloride homeostasis that may impact the future of heart failure care.

New Strategies for Volume Control in Patients with Diabetes Mellitus, a Narrative Review

Sodium is reabsorbed all along the renal tubules. The positive impacts of sodium-glucose cotransporter-2 inhibitors (SGLT2i), angiotensin receptor neprilysin inhibitor (ARNI) and mineralocorticoid receptor antagonists (MRA) on hard renal and/or cardiac endpoints calls for the role of diuretics in nephroprotection and cardioprotection in patients with diabetes mellitus to be reviewed. Here, we review: (a) the mechanisms of action of the available natriuretics; (b) the physiological adaptations to chronic loop diuretic usage that lead to increased sodium reabsorption in the proximal and distal convoluted tubules; (c) the physiology of sodium retention in patients with diabetes mellitus; and (d) the mechanisms of aldosterone breakthrough. We show the rationale for combined diuretics to target not only the loop of Henle, but also the proximal and distal convoluted tubules. Indeed, higher residual proteinuria in patients treated with renin-angiotensin-aldosterone system (RAAS) blockers portends poorer renal and cardiovascular outcomes. Diuretics are known to optimize the reduction of proteinuria, in addition to RAAS blockers, but may favor aldosterone breakthrough in the absence of MRA. The aim of our study is to support a combined diuretics strategy to improve the management of patients with diabetes mellitus and chronic kidney disease or heart failure.

Curcumin Attenuates Hydrocephalus via Activation of E2F Transcription Factor 4

BACKGROUND

Recent studies have shown that curcumin can reduce the symptoms of hydrocephalus. However, the underlying mechanisms remain unclear. Our previous studies demonstrated that E2F transcription factor 4 (E2F4) protein plays an important role in hydrocephalus; hence, we hypothesized that E2F4 may involve in curcumin mediated anti-hydrocephalus benefits.

METHODS

E2F4 expression and functions in different human tissues and cell lines were determined and analyzed using the all RNA-seq and ChIP-seq sample and signature search database and ChIP-atlas database. Hydrocephalus mouse model was established through stereotactic injection of shE2F4 into frontal cortex. Mice were treated with curcumin, and then hydrocephalus severity, the expression of E2F4, and downstream targets were analyzed.

RESULTS

E2F4 was highly expressed in the nervous system, which was downregulated in the bran of hydrocephalus patients. Knockdown E2F4 in mice could mimic the phenotype of human hydrocephalus. Upon curcumin administration, E2F4 expression level was increased, and the hydrocephalus severity score was significantly decreased in mouse model. Mechanistically, curcumin attenuated hydrocephalus through activating E2F4 signaling pathway.

CONCLUSION

Curcumin suppresses hydrocephalus progression via activation of E2F4, which could be a target for hydrocephalus treatment.

The Effect of Add-on Acetazolamide to Conventional Diuretics for Diuretic-resistant Edema Complicated with Hypercapnia: A Report of Two Cases

We herein report two cases in which add-on acetazolamide to furosemide was effective for diuretic-resistant volume overload and hypercapnia. Case 1 was a woman in her 40s presenting with volume overload due to the nephrotic syndrome with diabetes mellitus. Case 2 was a man in his 60s with fluid overload and non-nephrotic proteinuria and sepsis. In both cases, although fluid overload was resistant to high-dose loop diuretics and complicated with hypercapnia due to pulmonary effusion, add-on acetazolamide administration resulted in symptom resolution. The additional effect of acetazolamide occurred regardless of the degree of proteinuria and kidney function.

Pathophysiology, Evaluation, and Management of Metabolic Alkalosis

Metabolic alkalosis is an increase in blood pH to >7.45 due to a primary increase in serum bicarbonate (HCO3 -). Metabolic alkalosis results from alkali accumulation or acid loss, and it is associated with a secondary increase in carbon dioxide arterial pressure (PaCO2). Metabolic alkalosis is a common acid-base disorder, especially in critically ill patients. The pathogenesis of chronic metabolic alkalosis includes two derangements, generation of metabolic alkalosis via gain of alkali or loss of acid and maintenance of metabolic alkalosis by increased tubular HCO3 - reabsorption (failure of the kidneys to excrete excess alkali). Metabolic alkalosis is the most common acid-base disorder in hospitalized patients, particularly in the surgical critical care unit. Mortality increases as pH increases.

Usefulness of acetazolamide in the management of diuretic resistance

Worsening symptoms and fluid overload are the hallmarks of heart failure (HF) decompensation, and fluid removal is central to improvement. Despite high-dose loop diuretics, patients with decompensated HF may develop suboptimal diuresis/diuretic resistance. Sequential nephron blockade with a combination of loop and thiazide/thiazide-like diuretics may be insufficient, resulting in poor outcomes. We present a case wherein urine output improved significantly with acetazolamide. Although the diuretic capacity of acetazolamide is weak on its own, it might be efficient in aiding the efficacy of loop diuretics. We discuss the pathophysiological basis and evidence behind its potential role in diuretic resistance. Drawing from current understanding, we propose a stepwise approach to diuresis in such patients.

SGLT2 Inhibitor: Not a Traditional Diuretic for Heart Failure

Recent studies have shown impressive cardiovascular health benefits in individuals treated with SGLT2 inhibitors (SGLT2i) regardless of diabetic status. The underlying mechanisms driving these benefits are not well understood. Recently in Circulation, Griffin et al. (2020) reported the first human study investigating the diuretic effect of empagliflozin.

Diuretic Resistance in Heart Failure

Decompensated heart failure accounts for approximately 1 million hospitalizations in the United States annually, and this number is expected to increase significantly in the near future. Diuretics provide the initial management in most patients with fluid overload. However, the development of diuretic resistance remains a significant challenge in the treatment of heart failure. Due to the lack of a standard definition, the prevalence of this phenomenon remains difficult to determine, with some estimates suggesting that 25-30% of patients with heart failure have diuretic resistance. Certain characteristics, including low systolic blood pressures, renal impairment, and atherosclerotic disease, help predict the development of diuretic resistance. The underlying pathophysiology is likely multifactorial, with pharmacokinetic alterations, hormonal dysregulation, and the cardiorenal syndrome having significant roles. The therapeutic approach to this common problem typically involves increases in the diuretic dose and/or frequency, sequential nephron blockade, and mechanical fluid movement removal with ultrafiltration or peritoneal dialysis. Paracentesis is potentially useful in patients with intra-abdominal hypertension.

Impact of Moderate Sodium Restriction and Hydrochlorothiazide on Iodine Excretion in Diabetic Kidney Disease: Data from a Randomized Cross-Over Trial

Sodium restriction may potentially reduce iodine intake. This study aimed to determine the effect of sodium restriction (dietary counseling) on 24-h urinary iodine excretion. Diuretics provide an alternative to sodium restriction and are frequently added to sodium restriction, so the effects of hydrochlorothiazide (50 mg daily) and combined therapy were also studied. We performed a post-hoc analysis of a Dutch multi-center, randomized cross-over trial in 45 patients with diabetic kidney disease with a mean age of 65 ± 9 years, mean eGFR of 65 ± 27 mL/min/1.73 m², median albuminuria of 648 [230–2008] mg/24 h and 84% were male. During regular sodium intake with placebo, mean 24 h urinary sodium and iodine excretion were 224 ± 76 mmol/24 h and 252 ± 94 ug/24 h, respectively (r = 0.52, p < 0.001). Mean iodine excretion did not change significantly if sodium restriction and hydrochlorothiazide were applied separately; mean difference −8 ug/day (95% CI −38, 22; p = 0.6) and 14 ug/day (95% CI −24, 52; p = 0.5), respectively. Combined therapy induced a significant decrease in mean iodine excretion (−37 ug/day; 95% CI −67, −7; p = 0.02), yet this was not seen to a clinically meaningful level. The number of patients with an estimated intake below recommended daily allowances did not differ significantly between the four treatment periods (p = 0.3). These findings show that sodium restriction is not a risk factor for iodine deficiency.

Acetazolamide to increase natriuresis in congestive heart failure at high risk for diuretic resistance

AIMS

To investigate the effects of acetazolamide on natriuresis, decongestion, kidney function and neurohumoral activation in acute heart failure (AHF).

METHODS AND RESULTS

This prospective, two-centre study included 34 AHF patients on loop diuretics with volume overload. All had a serum sodium concentration < 135 mmol/L and/or serum urea/creatinine ratio > 50 and/or an admission serum creatinine increase of > 0.3 mg/dL compared to baseline. Patients were randomised towards acetazolamide 250-500 mg daily plus bumetanide 1-2 mg bid vs. high-dose loop diuretics (bumetanide bid with daily dose twice the oral maintenance dose). The primary endpoint was natriuresis after 24 h. Natriuresis after 24 h was similar in the combinational treatment vs. loop diuretic only arm (264 ± 126 vs. 234 ± 133 mmol; P = 0.515). Loop diuretic efficiency, defined as natriuresis corrected for loop diuretic dose, was higher in the group receiving acetazolamide (84 ± 46 vs. 52 ± 42 mmol/mg bumetanide; P = 0.048). More patients in the combinational treatment arm had an increase in serum creatinine levels > 0.3 mg/dL (P = 0.046). N-terminal pro-B-type natriuretic peptide reduction and peak neurohumoral activation within 72 h were comparable among treatment arms. There was a non-significant trend towards lower all-cause mortality or heart failure readmissions in the group receiving acetazolamide with low-dose loop diuretics vs. high-dose loop diuretic monotherapy (P = 0.098).

CONCLUSION

Addition of acetazolamide increases the natriuretic response to loop diuretics compared to an increase in loop diuretic dose in AHF at high risk for diuretic resistance.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01973335.

Brain Edema Formation and Functional Outcome After Surgical Decompression in Murine Closed Head Injury Are Modulated by Acetazolamide Administration

Acetazolamide (ACZ), carbonic anhydrase inhibitor, has been successfully applied in several neurosurgical conditions for diagnostic or therapeutic purposes. Furthermore, neuroprotective and anti-edematous properties of ACZ have been postulated. However, its use in traumatic brain injury (TBI) is limited, since ACZ-caused vasodilatation according to the Monro-Kellie doctrine may lead to increased intracranial blood volume / raise of intracranial pressure. We hypothesized that these negative effects of ACZ will be reduced or prevented, if the drug is administered after already performed decompression. To test this hypothesis, we used a mouse model of closed head injury (CHI) and decompressive craniectomy (DC). Mice were assigned into following experimental groups: sham, DC, CHI, CHI+ACZ, CHI+DC, and CHI+DC+ACZ (n = 8 each group). 1d and 3d post injury, the neurological function was assessed according to Neurological Severity Score (NSS) and Beam Balance Score (BBS). At the same time points, brain edema was quantified by MRI investigations. Functional impairment and edema volume were compared between groups and over time. Among the animals without skull decompression, the group additionally treated with acetazolamide demonstrated the most severe functional impairment. This pattern was reversed among the mice with decompressive craniectomy: CHI+DC treated but not CHI+DC+ACZ treated animals showed a significant neurological deficit. Accordingly, radiological assessment revealed most severe edema formation in the CHI+DC group while in CHI+DC+ACZ animals, volume of brain edema did not differ from DC-only animals. In our CHI model, the response to acetazolamide treatment varies between animals with decompressive craniectomy and those without surgical treatment. Opening the cranial vault potentially creates an opportunity for acetazolamide to exert its beneficial effects while vasodilatation-related risks are attenuated. Therefore, we recommend further exploration of this potentially beneficial drug in translational research projects.

Acetazolamide Therapy in Patients with Heart Failure: A Meta-Analysis

Background and objectives: Fluid overload and central sleep apnea are highly prevalent in patients with heart failure (HF). We performed this meta-analysis to assess the effects of acetazolamide therapy on acid/base balance and apnea indexes. Methods: A literature search was conducted using EMBASE, MEDLINE, and Cochrane Database from inception through 18 November 2017 to identify studies evaluating the use of acetazolamide in HF. Study results were analyzed using a random effects model. The protocol for this systematic review is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42017065401). Results: Nine studies (three randomized controlled trials and six cohort studies) with a total of 229 HF patients were enrolled. After acetazolamide treatment, there were significant decreases in serum pH (mean difference (MD) of −0.04 (95% CI, −0.06 to −0.02)), pCO₂ (MD of −2.06 mmHg (95% CI, −3.60 to −0.53 mmHg)), and serum bicarbonate levels (MD of −6.42 mmol/L (95% CI, −10.05 to −2.79 mmol/L)). When compared to a placebo, acetazolamide significantly increased natriuresis (standardized mean difference (SMD) of 0.67 (95% CI, 0.08 to 1.27)), and decreased the apnea-hypopnea index (AHI) (SMD of −1.06 (95% CI, −1.75 to −0.36)) and central apnea index (CAI) (SMD of −1.10 (95% CI, −1.80 to −0.40)). Egger’s regression asymmetry tests revealed no publication bias with p = 0.20, 0.75 and 0.59 for analysis of the changes in pH, pCO₂, and serum bicarbonate levels with use of acetazolamide in HF patients. Conclusion: Our study demonstrates significant reduction in serum pH, increase in natriuresis, and improvements in apnea indexes with use of acetazolamide among HF patients.

Nephrotic Syndrome: Oedema Formation and Its Treatment With Diuretics

Oedema is a defining element of the nephrotic syndrome. Its' management varies considerably between clinicians, with no national or international clinical guidelines, and hence variable outcomes. Oedema may have serious sequelae such as immobility, skin breakdown and local or systemic infection. Treatment of nephrotic oedema is often of limited efficacy, with frequent side-effects and interactions with other pharmacotherapy. Here, we describe the current paradigms of oedema in nephrosis, including insights into emerging mechanisms such as the role of the abnormal activation of the epithelial sodium channel in the collecting duct. We then discuss the physiological basis for traditional and novel therapies for the treatment of nephrotic oedema. Despite being the cardinal symptom of nephrosis, few clinical studies guide clinicians to the rational use of therapy. This is reflected in the scarcity of publications in this field; it is time to undertake new clinical trials to direct clinical practice.

Tuberous sclerosis complex exhibits a new renal cystogenic mechanism

Tuberous sclerosis complex (TSC) is a tumor predisposition syndrome with significant renal cystic and solid tumor disease. While the most common renal tumor in TSC, the angiomyolipoma, exhibits a loss of heterozygosity associated with disease, we have discovered that the renal cystic epithelium is composed of type A intercalated cells that have an intact Tsc gene that have been induced to exhibit Tsc-mutant disease phenotype. This mechanism appears to be different than that for ADPKD. The murine models described here closely resemble the human disease and both appear to be mTORC1 inhibitor responsive. The induction signaling driving cystogenesis may be mediated by extracellular vesicle trafficking.

Editor's Choice-Diuretic resistance in acute heart failure

Diuretic resistance is a powerful predictor of adverse outcome in acute heart failure (AHF), irrespectively of underlying glomerular filtration rate. Metrics of diuretic efficacy such as natriuresis, urine output, weight loss, net fluid balance, or fractional sodium excretion, differ in their risk for measurement error, convenience, and biological plausibility, which should be taken into account when interpreting their results. Loop diuretic resistance in AHF has multiple causes including altered drug pharmacokinetics, impaired renal perfusion and effective circulatory volume, neurohumoral activation, post-diuretic sodium retention, the braking phenomenon and functional as well as structural adaptations in the nephron. Ideally, these mechanisms should guide specific treatment decisions with the goal of achieving complete decongestion. Therefore, volume overload needs to be identified correctly to avoid poor diuretic response due to electrolyte depletion or dehydration. Next, renal perfusion should be optimised if possible and loop diuretics should be prescribed above their threshold dose. Addition of thiazide-type diuretics should be considered when a progressive decrease in loop diuretic efficacy is observed with prolonged use (i.e., the braking phenomenon). Furthermore, thiazide-type diuretics are a useful addition in patients with low glomerular filtration rate. However, they limit free water excretion and are relatively contraindicated in cases of hypotonic hyponatremia, where acetazolamide is the better option. Finally, ultrafiltration should be considered in patients with refractory diuretic resistance as persistent volume overload after decongestive treatment is associated with worse outcomes. Whether more upfront use of any of these individually tailored decongestion strategies is superior to monotherapy with loop diuretics remains to be shown by adequately powered randomised clinical trials.

Probenecid Pre-treatment Downregulates the Kidney Cl-/HCO3- Exchanger (Pendrin) and Potentiates Hydrochlorothiazide-Induced Diuresis

Background: Probenecid is a uricosuric agent that in addition to exerting a positive ionotropic effect in the heart, blocks the ATP transporter Pannexin 1 and inhibits the Cl-/HCO3- exchanger, pendrin. In the kidney, pendrin blunts the loss of salt wasting secondary to the inhibition of the thiazide-sensitive Na+-Cl- co-transporter (NCC/SLC12A3). Hypothesis: Pre-treatment with probenecid down-regulates pendrin; therefore, leaving NCC as the main salt absorbing transporter in the distal nephron, and hence enhances the hydrochlorothiazide (HCTZ)-induced diuresis. Methods: Daily balance studies, blood and urine chemical analysis, immunofluorescence, as well as western and northern blot analyses were utilized to examine the effects of probenecid alone (at 250 mg/kg/day) or in combination with HCTZ (at 40 mg/kg/day) on kidney function and on salt and water transporters in the collecting duct. Results: Male Sprague Dawley rats were subjected to three different protocols: (1) HCTZ for 4 days, (2) probenecid for 10 days, and (3) primed with probenecid for 6 days followed by probenecid and HCTZ for 4 additional days. Treatment protocol 1 (HCTZ for 4 days) only mildly increased the urine volume (U Vol) from a baseline of 9.8-13.4 ml/day. In response to treatment protocol 2 (probenecid for 10 days), U Vol increased to 15.9 ml/24 h. Treatment protocol 3 (probenecid for 6 days followed by probenecid and HCTZ for 4 additional days) increased the U Vol to 42.9 ml/day on day 4 of co-treatment with HCTZ and probenecid (compared to probenecid p = 0.003, n = 5 or HCTZ alone p = 0.001, n = 5). Probenecid treatment at 250 mg/kg/day downregulated the expression of pendrin and led to a decrease in AQP2 expression. Enhanced diuresis by probenecid plus HCTZ was not associated with volume depletion. Conclusion: Probenecid pre-treatment downregulates pendrin and robustly enhances diuresis by HCTZ-mediated NCC inhibition in kidney.

Acetazolamide as Add-on Diuretic Therapy in Exacerbations of Chronic Heart Failure: a Pilot Study

Background

Congestion is the main cause of morbidity in patients with heart failure. Treatment of fluid overload is often challenging in everyday clinical practice.

Objective

The aim of this study was to determine the diuretic effect of acetazolamide in patients with exacerbations of chronic heart failure, in addition to their stable diuretic therapy.

Methods

This was a single-center, unblinded study. Patients hospitalized with chronic heart failure exacerbations, with left ventricular ejection fraction (EF) < 50% and signs of volume overload, with a stable dose of diuretics anticipated by the attending physician over the next 4 days, were considered eligible for the study. On day 1, patients were randomized to receive acetazolamide orally, once daily (dose-adjusted to body weight) or no treatment (control group) as add-on diuretic therapy, on days 2 and 3. Diuresis, natriuresis, fluid balance, and symptoms were assessed daily, up to day 4.

Results

Twenty patients (mean ± standard deviation age 72 ± 11.6 years; 85% men; mean EF 33.8 ± 11.4%; mean N-terminal pro-B-type natriuretic peptide 8064 ± 5593 pg/mL; mean intravenous furosemide dose 105 ± 55 mg) were enrolled. Diuresis, natriuresis, fluid balance, and symptoms were stable on days 1–4 in the control group. An increase in diuresis and natriuresis, and a greater change in fluid balance after administration of acetazolamide, were observed in patients randomized to acetazolamide. On day 4, there was a significant difference in fluid balance between the acetazolamide and control groups (−666 ± 1194 mL vs. +332 ± 705 mL; p = 0.035), and dyspnea was lower in patients receiving acetazolamide (visual scale, p < 0.001; 5-point Likert scale, 1.444 vs. 2.222; p = 0.04)

Conclusions

In this pilot study, the addition of acetazolamide to the background diuretic regimen in patients with chronic heart failure exacerbations produced an additional diuretic effect and alleviation of dyspnea.

SGLT-2 Inhibitors in Heart Failure: Implications for the Kidneys

PURPOSE OF REVIEW

This review aims to summarize the renal effects of sodium-glucose transporter-2 (SGLT-2) inhibitors and their potential implications in heart failure pathophysiology.

RECENT FINDINGS

In patients with diabetes and established atherosclerosis, the SGLT-2 inhibitor empagliflozin versus placebo significantly reduced the rate of heart failure admissions with 35%. Moreover, empagliflozin slowed kidney disease progression and reduced the need for renal replacement therapy. SGLT-2 inhibitors inhibit proximal tubular sodium and chloride reabsorption, leading to increased nephron flux throughout the distal renal tubules, most notably at the level of the macula densa. Afferent arteriolar vasoconstriction is promoted through tubulo-glomerular feedback and reduces glomerular capillary hydrostatic pressure, relieving podocyte stress and explaining renal preservation. Further, plasma volume is contracted and natriuresis promoted without inducing neurohumoral activation. Finally, SGLT-2 inhibitors may improve endothelial function and energy metabolism efficiency. Together, these promising features place them as a potential novel treatment for heart failure.

Ablation of the Cl-/HCO3- Exchanger Pendrin Enhances Hydrochlorothiazide-Induced Diuresis

BACKGROUND/AIMS

The Cl-/HCO3- exchanger pendrin and the thiazide-sensitive Na-Cl cotransporter NCC are expressed in the kidney distal nephron and mediate salt absorption. We hypothesized that deletion of pendrin leaves NCC as the major salt absorbing transporter in the distal nephron and therefore enhances salt excretion by hydrochlorothiazide (HCTZ).

METHODS

Metabolic cage studies were performed in wild type, pendrin KO and NCC KO mice at baseline and following HCTZ treatment. In parallel studies, systemic blood pressure was measured in mice treated with HCTZ with the tail cuff method.

RESULTS

Urine output, salt excretion and water intake were comparable in all groups under baseline condition. Urine output and water intake increased significantly only in pendrin KO mice in response to HCTZ, but not in WT or NCC KO mice. Sodium and chloride excretion increased in HCTZ-treated pendrin KO mice, but they remained unchanged in WT or NCC KO mice. Pendrin KO mice treated with HCTZ developed volume depletion, as determined by increased expression of renin mRNA and protein. The expression of ENaC and pendrin increased in HCTZ-treated WT mice. HCTZ treatment did not significantly modify blood pressure in any of the experimental group.

CONCLUSION

The ablation of the Cl-/HCO3- exchanger Pendrin enhances the magnitude of salt wasting by HCTZ.

The non-diuretic hypotensive effects of thiazides are enhanced during volume depletion states

Thiazide derivatives including Hydrochlorothiazide (HCTZ) represent the most common treatment of mild to moderate hypertension. Thiazides initially enhance diuresis via inhibition of the kidney Na+-Cl- Cotransporter (NCC). However, chronic volume depletion and diuresis are minimal while lowered blood pressure (BP) is maintained on thiazides. Thus, a vasodilator action of thiazides is proposed, likely via Ca2+-activated K+ (BK) channels in vascular smooth muscles. This study ascertains the role of volume depletion induced by salt restriction or salt wasting in NCC KO mice on the non-diuretic hypotensive action of HCTZ. HCTZ (20mg/kg s.c.) lowered BP in 1) NCC KO on a salt restricted diet but not with normal diet; 2) in volume depleted but not in volume resuscitated pendrin/NCC dKO mice; the BP reduction occurs without any enhancement in salt excretion or reduction in cardiac output. HCTZ still lowered BP following treatment of NCC KO on salt restricted diet with paxilline (8 mg/kg, i.p.), a BK channel blocker, and in BK KO and BK/NCC dKO mice on salt restricted diet. In aortic rings from NCC KO mice on normal and low salt diet, HCTZ did not alter and minimally decreased maximal phenylephrine contraction, respectively, while contractile sensitivity remained unchanged. These results demonstrate 1) the non-diuretic hypotensive effects of thiazides are augmented with volume depletion and 2) that the BP reduction is likely the result of HCTZ inhibition of vasoconstriction through a pathway dependent on factors present in vivo, is unrelated to BK channel activation, and involves processes associated with intravascular volume depletion.

Acetazolamide and Hydrochlorothiazide Followed by Furosemide Versus Furosemide and Hydrochlorothiazide Followed by Furosemide for the Treatment of Adults With Nephrotic Edema: A Randomized Trial

BACKGROUND

Nephrotic edema is considered refractory if it does not respond to maximum or near-maximum doses of loop diuretics. This condition can be treated with loop diuretics and thiazides. However, animal studies show that the simultaneous downregulation of pendrin with acetazolamide and inhibition of the sodium-chloride cotransporter with hydrochlorothiazide generates significant diuresis, and furosemide administration following a pendrin inhibitor potentiates furosemide's diuretic effect. Therefore, we performed this study to compare the efficacy of acetazolamide and hydrochlorothiazide followed by furosemide versus furosemide and hydrochlorothiazide followed by furosemide for treatment of refractory nephrotic edema.

STUDY DESIGN

Randomized, double-blind, 2-arm, parallel trial.

SETTING & PARTICIPANTS

20 patients with refractory nephrotic edema despite treatment with 80mg of furosemide daily and creatinine clearance > 60mL/min.

INTERVENTION

Patients were randomly assigned to 2 groups: group 1 (n=10) received 250mg of acetazolamide and 50mg of hydrochlorothiazide daily and group 2 (n=10) received 40mg of furosemide and 50mg of hydrochlorothiazide daily for 1 week in phase 1. In phase 2, both groups received 40mg of furosemide daily for 2 weeks.

OUTCOMES

The primary outcome was absolute change in weight before and at the end of each phase.

MEASUREMENTS

Weight and 24-hour urine volume at baseline and the end of each phase.

RESULTS

The mean weight decrease was of significantly larger magnitude in group 1 compared with group 2 at the end of phase 1 (-1.4±0.52 [SD] vs -0.65±0.41kg; P=0.001) and phase 2 (-1.6±0.84 vs -0.5±0.47kg; P=0.005). The increase in 24-hour urine volume was also significantly higher in group 1 at the end of phase 2.

LIMITATIONS

Small sample size, short follow-up duration, and lack of serum bicarbonate and chloride measurement.

CONCLUSIONS

Acetazolamide and hydrochlorothiazide followed by furosemide is more effective than furosemide and hydrochlorothiazide followed by furosemide for the treatment of refractory nephrotic edema.

Acetazolamide Therapy for Metabolic Alkalosis in Pediatric Intensive Care Patients

OBJECTIVE

Patients in PICUs frequently present hypochloremic metabolic alkalosis secondary to loop diuretic treatment, especially those undergoing cardiac surgery. This study evaluates the effectiveness of acetazolamide therapy for metabolic alkalosis in PICU patients.

DESIGN

Retrospective, observational study.

SETTING

A tertiary care children's hospital PICU.

PATIENTS

Children receiving at least a 2-day course of enteral acetazolamide.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic variables, diuretic treatment and doses of acetazolamide, urine output, serum electrolytes, urea and creatinine, acid-base excess, pH, and use of mechanical ventilation during treatment were collected. Patients were studied according to their pathology (postoperative cardiac surgery, decompensated heart failure, or respiratory disease). A total of 78 episodes in 58 patients were identified: 48 were carried out in cardiac postoperative patients, 22 in decompensated heart failure, and eight in respiratory patients. All patients received loop diuretics. A decrease in pH and PCO2 in the first 72 hours, a decrease in serum HCO3 (mean, 4.65 ± 4.83; p < 0.001), and an increase in anion gap values were observed. Urine output increased in cardiac postoperative patients (4.5 ± 2.2 vs 5.1 ± 2.0; p = 0.020), whereas diuretic treatment was reduced in cardiac patients. There was no significant difference in serum electrolytes, blood urea, creatinine, nor chloride after the administration of acetazolamide from baseline. Acetazolamide treatment was well tolerated in all patients.

CONCLUSIONS

Acetazolamide decreases serum HCO3 and PCO2 in PICU cardiac patients with metabolic alkalosis secondary to diuretic therapy. Cardiac postoperative patients present a significant increase in urine output after acetazolamide treatment.

Diuretic Resistance

Diuretic resistance is defined as a failure to achieve the therapeutically desired reduction in edema despite a full dose of diuretic. The causes of diuretic resistance include poor adherence to drug therapy or dietary sodium restriction, pharmacokinetic issues, and compensatory increases in sodium reabsorption in nephron sites that are not blocked by the diuretic. To illustrate the pathophysiology and management of diuretic resistance, we describe a patient with nephrotic syndrome. This patient presented with generalized pitting edema and weight gain despite the use of oral loop diuretics. Nephrotic syndrome may cause mucosal edema of the intestine, limiting the absorption of diuretics. In addition, the patient's kidney function had deteriorated, impairing the tubular secretion of diuretics. He was admitted for intravenous loop diuretic treatment. However, this was ineffective, likely due to compensatory sodium reabsorption by other tubular segments. The combination of loop diuretics with triamterene, a blocker of the epithelial sodium channel, effectively reduced body weight and edema. Recent data suggest that plasmin in nephrotic urine can activate the epithelial sodium channel, potentially contributing to the diuretic resistance in this patient. This case is used to illustrate and review the mechanisms of, and possible interventions for, diuretic resistance.

Prostaglandin-E2 Mediated Increase in Calcium and Phosphate Excretion in a Mouse Model of Distal Nephron Salt Wasting

Contribution of salt wasting and volume depletion to the pathogenesis of hypercalciuria and hyperphosphaturia is poorly understood. Pendrin/NCC double KO (pendrin/NCC-dKO) mice display severe salt wasting under basal conditions and develop profound volume depletion, prerenal renal failure, and metabolic alkalosis and are growth retarded. Microscopic examination of the kidneys of pendrin/NCC-dKO mice revealed the presence of calcium phosphate deposits in the medullary collecting ducts, along with increased urinary calcium and phosphate excretion. Confirmatory studies revealed decreases in the expression levels of sodium phosphate transporter-2 isoforms a and c, increases in the expression of cytochrome p450 family 4a isotypes 12 a and b, as well as prostaglandin E synthase 1, and cyclooxygenases 1 and 2. Pendrin/NCC-dKO animals also had a significant increase in urinary prostaglandin E2 (PGE-2) and renal content of 20-hydroxyeicosatetraenoic acid (20-HETE) levels. Pendrin/NCC-dKO animals exhibit reduced expression levels of the sodium/potassium/2chloride co-transporter 2 (NKCC2) in their medullary thick ascending limb. Further assessment of the renal expression of NKCC2 isoforms by quantitative real time PCR (qRT-PCR) reveled that compared to WT mice, the expression of NKCC2 isotype F was significantly reduced in pendrin/NCC-dKO mice. Provision of a high salt diet to rectify volume depletion or inhibition of PGE-2 synthesis by indomethacin, but not inhibition of 20-HETE generation by HET0016, significantly improved hypercalciuria and salt wasting in pendrin/NCC dKO mice. Both high salt diet and indomethacin treatment also corrected the alterations in NKCC2 isotype expression in pendrin/NCC-dKO mice. We propose that severe salt wasting and volume depletion, irrespective of the primary originating nephron segment, can secondarily impair the reabsorption of salt and calcium in the thick ascending limb of Henle and/or proximal tubule, and reabsorption of sodium and phosphate in the proximal tubule via processes that are mediated by PGE-2.

The Role of Epithelial Sodium Channel ENaC and the Apical Cl-/HCO3- Exchanger Pendrin in Compensatory Salt Reabsorption in the Setting of Na-Cl Cotransporter (NCC) Inactivation

BACKGROUND

The absence of NCC does not cause significant salt wasting in NCC deficient mice under basal conditions. We hypothesized that ENaC and pendrin play important roles in compensatory salt absorption in the setting of NCC inactivation, and their inhibition and/or downregulation can cause significant salt wasting in NCC KO mice.

METHODS

WT and NCC KO mice were treated with a daily injection of either amiloride, an inhibitor of ENaC, or acetazolamide (ACTZ), a blocker of salt and bicarbonate reabsorption in the proximal tubule and an inhibitor of carbonic anhydrases in proximal tubule and intercalated cells, or a combination of acetazolamide plus amiloride for defined durations. Animals were subjected to daily balance studies. At the end of treatment, kidneys were harvested and examined. Blood samples were collected for electrolytes and acid base analysis.

RESULTS

Amiloride injection significantly increased the urine output (UO) in NCC KO mice (from 1.3 ml/day before to 2.5 ml/day after amiloride, p<0.03, n = 4) but caused only a slight change in UO in WT mice (p>0.05). The increase in UO in NCC KO mice was associated with a significant increase in sodium excretion (from 0.25 mmol/24 hrs at baseline to 0.35 mmol/24 hrs after amiloride injection, p<0.05, n = 4). Daily treatment with ACTZ for 6 days resulted in >80% reduction of kidney pendrin expression in both WT and NCC KO mice. However, ACTZ treatment noticeably increased urine output and salt excretion only in NCC KO mice (with urine output increasing from a baseline of 1.1 ml/day to 2.3 ml/day and sodium excretion increasing from 0.22 mmole/day before to 0.31 mmole/day after ACTZ) in NCC KO mice; both parameters were significantly higher than in WT mice. Western blot analysis demonstrated significant enhancement in ENaC expression in medulla and cortex of NCC KO and WT mice in response to ACTZ injection for 6 days, and treatment with amiloride in ACTZ-pretreated mice caused a robust increase in salt excretion in both NCC KO and WT mice. Pendrin KO mice did not display a significant increase in urine output or salt excretion after treatment with amiloride or ACTZ.

CONCLUSION

1. ENaC plays an important role in salt reabsorption in NCC KO mice. 2. NCC contributes to compensatory salt reabsorption in the setting of carbonic anhydrase inhibition, which is associated with increased delivery of salt from the proximal tubule and the down regulation of pendrin. 3. ENaC is upregulated by ACTZ treatment and its inhibition by amiloride causes significant diuresis in NCC KO and WT mice. Despite being considered mild agents individually, we propose that the combination of acetazolamide and amiloride in the setting of NCC inhibition (i.e., hydrochlorothiazide) will be a powerful diuretic regimen.

Pendrin, an anion exchanger on lung epithelial cells, could be a novel target for lipopolysaccharide-induced acute lung injury mice

OBJECTIVE

The aim of this study is to evaluate the role of pendrin in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) and to explore whether pendrin expression existing on alveolar cells.

METHODS

ALI C57BL/6 mice model induced by lipopolysaccharide (LPS) was established. The expression of pendrin in lung was analyzed by RT-PCR and western blotting methods, the changes of lung inflammatory parameters and pathology were observed, the cellular distribution of pendrin in the lung was determined using immunofluorescence. Statistical comparisons between groups were made by two-tailed Student's t-test.

RESULTS

Enhanced expression of the slc26a4 gene and production of pendrin in lungs of LPS-induced ALI mice were confirmed. In comparison with vehicle-control mice, methazolamide treatment mitigated lung inflammatory parameters and pathology. IL-6 and MCP-1 in lung tissues and BALF in methazolamide-treated mice were statistically decreased. Methazolamide treatment had significant effect on the total protein concentration in the BALF and the ratio of lung wet/dry weight. The percentage of macrophages in the BALF was increased. There was a low expression of pendrin in ATII.

CONCLUSIONS

Pendrin may be involved in pathological process of LPS-induced ALI. Inhibition of the pendrin function could be used to treat ALI. Airway epithelial cell may be a valuable therapeutic target for discovering and developing new drugs and/or new therapeutic strategies for the treatment of ALI/ARDS.

Insulin resistance and hypertension: new insights

Insulin resistance is associated with hypertension. Nakamura et al. demonstrate in rodents and humans with insulin resistance that while the stimulatory effect of insulin on glucose uptake in adipocytes, mediated via insulin receptor substrate 1 (IRS1), was severely diminished, its effect on salt reabsorption in the kidney proximal tubule, mediated via IRS2, was preserved. Compensatory hyperinsulinemia in individuals with insulin resistance may enhance salt absorption in the proximal tubule, resulting in a state of salt overload and hypertension.

Management of Cardio-Renal Syndrome and Diuretic Resistance

OPINION STATEMENT

Diuretic resistance in acute heart failure has emerged as a powerful predictor of adverse outcome, which is often independent of underlying glomerular filtration rate (GFR). Metrics of diuretic efficacy differ in their accuracy, convenience, and biological plausibility, which should be taken into account when interpreting their results. Loop diuretic efficacy depends on adequate delivery of both the pharmacological agent itself and its substrate (i.e., sodium chloride) to the loop diuretic site of action at the luminal side of the thick ascending limb of Henle's loop. This requires an adequate dosing strategy, with higher doses needed when GFR is low. Importantly, the kidneys are able only to regulate the effective circulatory volume. Thus, specific problems of intravascular volume depletion and poor cardiac output with impaired renal perfusion should be addressed. Addition of thiazide-type diuretics should be considered when a progressive decrease in loop diuretic efficacy is observed with prolonged use (i.e., the braking phenomenon). Furthermore, thiazide-type diuretics are a useful addition in patients with low GFR to maximally boost fractional sodium excretion when nephron perfusion is poor. However, thiazide-type diuretics limit free water excretion and should be withheld in cases of hypotonic hyponatremia. Mineralocorticoid receptor antagonists (MRA) and acetazolamide are interesting options to increase loop diuretic efficacy, but further study is needed to assess whether improved diuretic efficacy also translates into clinical outcome benefits. Finally, ultrafiltration should be considered in patients with refractory diuretic resistance as persistent volume overload after decongestive treatment is associated with worse outcomes. Whether more upfront use of individually tailored ultrafiltration is superior to pharmacological therapy remains to be shown by adequately powered randomized clinical trials.

The multiple roles of pendrin in the kidney

The [Formula: see text] exchanger pendrin (SLC26A4, PDS) is located on the apical membrane of B-intercalated cells in the kidney cortical collecting duct and the connecting tubules and mediates the secretion of bicarbonate and the reabsorption of chloride. Given its dual function of bicarbonate secretion and chloride reabsorption in the distal tubules, it was thought that pendrin plays important roles in systemic acid-base balance and electrolyte and vascular volume homeostasis under basal conditions. Mice with the genetic deletion of pendrin or humans with inactivating mutations in PDS gene, however, do not display excessive salt and fluid wasting or altered blood pressure under baseline conditions. Very recent reports have unmasked the basis of incongruity between the mild phenotype in mutant mice and the role of pendrin as an important player in salt reabsorption in the distal tubule. These studies demonstrate that pendrin and the Na-Cl cotransporter (NCC; SLC12A3) cross compensate for the loss of each other, therefore masking the role that each transporter plays in salt reabsorption under baseline conditions. In addition, pendrin regulates calcium reabsorption in the distal tubules. Furthermore, combined deletion of pendrin and NCC not only causes severe volume depletion but also results in profound calcium wasting and luminal calcification in medullary collecting ducts. Based on studies in pathophysiological states and the examination of genetically engineered mouse models, the evolving picture points to important roles for pendrin (SLC26A4) in kidney physiology and in disease states. This review summarizes recent advances in the characterization of pendrin and the multiple roles it plays in the kidney, with emphasis on its essential roles in several diverse physiological processes, including chloride homeostasis, vascular volume and blood pressure regulation, calcium excretion and kidney stone formation.

Epithelial anion transporter pendrin contributes to inflammatory lung pathology in mouse models of Bordetella pertussis infection

Pertussis disease, characterized by severe and prolonged coughing episodes, can progress to a critical stage with pulmonary inflammation and death in young infants. However, there are currently no effective treatments for pertussis. We previously studied the role of pertussis toxin (PT), an important Bordetella pertussis virulence factor, in lung transcriptional responses to B. pertussis infection in mouse models. One of the genes most highly upregulated in a PT-dependent manner encodes an epithelial transporter of bicarbonate, chloride, and thiocyanate, named pendrin, that contributes to asthma pathology. In this study, we found that pendrin expression is upregulated at both gene and protein levels in the lungs of B. pertussis-infected mice. Pendrin upregulation is associated with PT production by the bacteria and with interleukin-17A (IL-17A) production by the host. B. pertussis-infected pendrin knockout (KO) mice had higher lung bacterial loads than infected pendrin-expressing mice but had significantly reduced levels of lung inflammatory pathology. However, reduced pathology did not correlate with reduced inflammatory cytokine expression. Infected pendrin KO mice had higher levels of inflammatory cytokines and chemokines than infected pendrin-expressing mice, suggesting that these inflammatory mediators are less active in the airways in the absence of pendrin. In addition, treatment of B. pertussis-infected mice with the carbonic anhydrase inhibitor acetazolamide reduced lung inflammatory pathology without affecting pendrin synthesis or bacterial loads. Together these data suggest that PT contributes to pertussis pathology through the upregulation of pendrin, which promotes conditions favoring inflammatory pathology. Therefore, pendrin may represent a novel therapeutic target for treatment of pertussis disease.