Metabolic acidosis in chronic kidney disease: mere consequence or also culprit?

Acidosis-induced p38-kinase activation triggers an IL-6-mediated crosstalk of renal proximal tubule cells with fibroblasts leading to their inflammatory response

BACKGROUND

Local interstitial acidosis in chronic kidney disease (CKD) induces inflammatory responses and dedifferentiation of proximal tubule cells (PTCs), disrupting cellular crosstalk through cytokine and COX-2 metabolite secretion. This promotes a switch to an inflammatory fibroblast phenotype, further exacerbating inflammation and PTC dedifferentiation. p38-signaling and downstream transcription factors, including P-CREB and c-fos, contribute to these responses. This study investigates the impact of acidosis on inflammatory responses in PTCs and fibroblasts, focusing on cellular crosstalk and the role of p38-signaling.

METHODS

HK-2 (human PTCs) and CCD-1092Sk (human fibroblasts) were exposed to acidic or control media in mono- and coculture for 30 min, 3 h, or 48 h. Protein expression of IL-6, phosphorylated (P-) and total CREB, P- and total SRF, c-fos, and P- and total p38 was analyzed by western blot. IL-6 secretion was measured using ELISA. The impact of p38 and IL-6 receptor activity was assessed by pharmacological intervention.

RESULTS

In coculture, acidosis initially caused a transient decrease in IL-6 secretion but significantly increased IL-6 levels after 48 h. Acidosis induced intracellular IL-6 expression in HK-2 cells within 3 h independent of culture conditions, with sustained IL-6 protein increase after 48 h only in coculture. Acidosis also enhanced P-CREB and c-fos expression in coculture during the first 3 h. Regardless of culture conditions, acidosis increased IL-6, c-fos, and P-SRF expression in CCDSK cells after 48 h. P-CREB and COX-2 expression were elevated in CCDSK in coculture. Acidosis-mediated effects on IL-6, P-CREB, and P-SRF expression were p38-dependent in both cell lines. Finally, we assessed the pH-dependency of IL-6 action and found that IL-6 addition increased COX-2 expression via the IL-6 receptor in acidic but not control media. Thus, acidosis enhances IL-6 secretion and potentiates its receptor-mediated biological effects.

CONCLUSION

This study identifies IL-6 as a key mediator of tubule-fibroblast crosstalk in an acidic milieu, promoting inflammatory processes. Acidosis induces IL-6 expression, secretion, and biological effects, with p38 kinase as a crucial mediator. If validated in vivo, these findings could enhance understanding of CKD and support early interventions.

Construction of risk prediction model and risk score table for infant heart failure hospital death based on white blood cell count to total protein ratio

The study analyzed 544 infants (1-36 months) with heart failure, aiming to correlate WBC/TP ratio with mortality and create a predictive model. Lasso regression identified significant mortality-associated clinical indices; logistic regression then built a death prediction model with an AUC of 0.755. Calibration and DCA curves indicated model accuracy and clinical utility. Risk stratification revealed higher mortality in the high-risk group, emphasizing WBC/TP as predictors and the model's value for early high-risk patient identification in infant heart failure.

[What is confirmed in the treatment of metabolic acidosis in chronic kidney disease?]

Precise regulation of the acid-base balance is essential for the functioning of various organs and physiological processes. Acid retention and metabolic acidosis (MA) are frequent complications of chronic kidney disease (CKD) and can also occur following kidney transplantation. In addition to dietary modifications, pharmacological interventions, most notably sodium bicarbonate, are employed to correct MA. While several studies have reported a beneficial effect of MA correction on the progression of CKD, the results remain inconsistent and the magnitude of the treatment effect may be limited. Importantly, no beneficial effect on graft function has been demonstrated after kidney transplantation. The MA is associated with impaired bone quality and although alkali treatment has generally shown positive effects on markers of bone metabolism, consistent changes in bone density have not been observed. Additionally, MA is linked to an increased incidence of cardiovascular events but so far there is a lack of interventional studies with definitive cardiovascular endpoints. Sodium bicarbonate may lead to sodium retention, potentially increasing blood pressure, although the data on this are inconclusive. One interventional study with notable limitations reported a positive effect of alkali treatment on mortality. Correction of MA has been suggested to positively impact protein and muscle catabolism, although no improvement in physical performance was observed in a geriatric population. Limited studies exist on the endocrinological effects of alkali treatment but these indicate a favorable impact on glucose metabolism and potential benefits for thyroid function in predialysis CKD patients. Given the overall low to moderate level of evidence supporting the benefits of alkali treatment, the current guidelines from Kidney Disease: Improving Global Outcomes (KDIGO) propose alkali treatment to prevent serum bicarbonate levels < 18 mmol/l (prior < 22 mmol/l) in adults and the resulting complications.

Advanced Gouty Nephropathy Complicated With Type 1 Renal Tubular Acidosis: A Case Report

This report describes the case of a 53-year-old woman with chronic kidney disease (CKD) exacerbated by a gout flare who presented with renal tubular acidosis (RTA), hypokalemia, and hyperuricemia. Despite outpatient management for gouty nephropathy, the patient experienced progressive hypokalemia, leading to hospitalization. Upon admission, she was diagnosed with type 1 RTA, characterized by metabolic acidosis and severe hypokalemia, refractory to initial potassium supplementation. The patient's medical history included gout, chronic renal failure, and other comorbidities, complicating her condition. Treatment included aggressive potassium replacement and ongoing management of her gout and CKD. Over several hospital days, her potassium levels stabilized, and she was discharged on oral potassium supplements. This case emphasizes the importance of monitoring electrolyte imbalances and managing uric acid levels in patients with chronic gout and kidney disease to prevent complications such as RTA. Comprehensive management strategies, including dietary and pharmacological interventions, are critical to prevent the progression of gouty nephropathy and improve patient outcomes.

Efficacy and safety of oral sodium bicarbonate in kidney-transplant recipients and non-transplant patients with chronic kidney disease: a systematic review and meta-analysis

Introduction

We investigated the efficacy and safety of oral sodium bicarbonate in kidney-transplant recipients and non-transplant patients with chronic kidney disease (CKD), which are currently unclear.

Methods

PubMed, Cochrane Library, Embase, and Web of Science were searched for randomized controlled trials investigating the efficacy and safety of sodium bicarbonate versus placebo or standard treatment in kidney-transplant and non-transplant patients with CKD.

Results

Sixteen studies of kidney-transplant recipients (two studies, 280 patients) and non-transplant patients with CKD (14 studies, 1,380 patients) were included. With non-transplant patients, sodium bicarbonate slowed kidney-function declines (standardized mean difference [SMD]: 0.49, 95% confidence interval [CI]: 0.14-0.85, p = 0.006) within ≥12 months (SMD: 0.75 [95% CI: 0.12-1.38], p = 0.02), baseline-serum bicarbonate <22 mmol/L (SMD: 0.41 [95% CI: 0.19-0.64], p = 0.0004) and increased serum-bicarbonate levels (mean difference [MD]: 2.35 [95% CI: 1.40-3.30], p < 0.00001). In kidney-transplant recipients, sodium bicarbonate did not preserve graft function (SMD: -0.07 [95% CI: -0.30-0.16], p = 0.56) but increased blood pH levels (MD: 0.02 [95% CI: 0.00-0.04], p = 0.02). No significant adverse events occurred in the kidney-transplant or non-transplant patients (risk ratio [RR]: 0.89, [95% CI: 0.47-1.67], p = 0.72; and RR 1.30 [95% CI: 0.84-2.00], p = 0.24, respectively). However, oral sodium bicarbonate correlated with increased diastolic pressure and worsened hypertension and edema (MD: 2.21 [95% CI: 0.67-3.75], p = 0.005; RR: 1.44 [95% CI: 1.11-1.88], p = 0.007; and RR: 1.28 [95% CI: 1.00-1.63], p = 0.05, respectively).

Discussion

Oral sodium bicarbonate may slow kidney-function decline in non-transplant patients with CKD taking sodium bicarbonate supplementation for ≥12 months or a baseline serum bicarbonate level of <22 mmol/L, without preserving graft function in kidney-transplant recipients. Sodium bicarbonate may increase diastolic pressure, and elevate a higher incidence of worsening hypertension and edema.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023413929.