Synthetic Antimicrobial Mimic CSA-13 Shields Kidneys in Sepsis Model

Acute kidney injury remains one of the most feared complications of sepsis, the dysregulated and life-threatening response to infection that kills millions of people worldwide each year. When pneumonia drives a patient into sepsis, the kidneys are frequently among the first organs to fail, and the resulting damage is strongly linked to prolonged intensive care stays, dialysis dependence, and death. Because conventional antibiotics can only do so much—and often carry nephrotoxic liabilities of their own—researchers have been searching for molecules that both attack bacteria and calm the destructive inflammatory storm that follows. A new study offers fresh evidence that a synthetic mimic of the body’s natural infection-fighting peptides may do exactly that, protecting kidney function and structure in a mouse model of severe bacterial pneumonia.

The research, published in The Journal of Antibiotics, focused on CSA-13, the prototype of a family of laboratory-designed molecules called ceragenins. Unlike antimicrobial peptides, which are short chains of amino acids that the innate immune system deploys against invading pathogens, ceragenins are small sterol-based compounds built to reproduce the membrane-disrupting activity of those peptides without the fragility that limits their clinical use. Natural peptides are easily degraded by proteases and can be inactivated by DNA and actin released from dying tissue, conditions abundant in infected lungs. Ceragenins were engineered to sidestep those weaknesses while retaining a positively charged surface that binds to and permeabilizes bacterial membranes, and to additionally modulate inflammatory signaling through pathways involving innate immune receptors.

To test whether CSA-13 could protect the kidneys during pneumonia-induced sepsis, the team, led by Ugur Aksu of Istanbul University together with colleagues at several Turkish institutions and Paul B. Savage of Brigham Young University, worked with female C57/BL6 mice randomly assigned to four experimental groups of six animals each. One group served as a healthy control, while a second was subjected to Pseudomonas pneumonia-induced sepsis and left untreated. The remaining two groups received sepsis induction followed by either a low or a high dose of CSA-13 delivered intraperitoneally, a route that allowed the compound to circulate systemically after the infection had taken hold. The design deliberately modeled a treatment scenario rather than prophylaxis, asking whether the ceragenin could intervene after septic injury had already begun.

The investigators then tracked three interlocking dimensions of sepsis-related renal damage. Renal injury was quantified using plasma cystatin C, a small protein widely regarded as a more sensitive and reliable marker of glomerular filtration than traditional creatinine measurements because it is produced at a constant rate and is not confounded by muscle mass in the same way. Inflammation was assessed by measuring interleukin-6 concentrations in kidney tissue, since IL-6 is a central cytokine amplifier of the septic response and elevated tissue levels correlate with worse outcomes in acute kidney injury. Finally, glycocalyx integrity was evaluated through plasma hyaluronan, a glycosaminoglycan that is shed into the bloodstream when the endothelial glycocalyx—a delicate gel-like layer coating the interior surface of blood vessels—is degraded during systemic inflammation.

The glycocalyx deserves particular attention because it has emerged in recent years as both a diagnostic window and a therapeutic target in sepsis. This carbohydrate-rich coating on endothelial cells acts as a barrier that regulates vascular permeability, limits inappropriate adhesion of leukocytes, and maintains the selective sieving properties of the glomerular filtration barrier in the kidney. During sepsis, enzymes and inflammatory mediators shred the glycocalyx, releasing fragments such as hyaluronan into the circulation and simultaneously leaving the vasculature leaky and prothrombotic. In the kidney, this shedding contributes to the breakdown of filtration barriers that defines acute kidney injury. A therapy that preserves or restores the glycocalyx could therefore interrupt a critical step in the cascade from infection to organ failure, which is precisely what the researchers hoped CSA-13 might achieve.

The results were striking in two of the three domains. Both the low and high doses of CSA-13 successfully restored plasma cystatin C toward normal levels, indicating that kidney function was substantially preserved despite the septic insult. Equally important, tissue levels of interleukin-6, which surged in untreated septic mice, fell back to values indistinguishable from those of healthy controls in animals receiving either dose of the ceragenin. This dual effect—preserving filtration capacity while suppressing a key inflammatory cytokine within the kidney itself—suggests that CSA-13 acts not merely as an antibiotic reducing bacterial load but also as an immunomodulatory agent dampening the local renal inflammatory response that drives tissue damage.

Histological examination reinforced the biochemical findings. Under the microscope, the kidneys of untreated septic mice displayed the expected hallmarks of acute injury, including disruption of cellular architecture and tissue disorganization. In contrast, mice treated with either dose of CSA-13 largely maintained cellular integrity, with renal tissue structure closely resembling that of the healthy control group. The consistency of the protection across both low and high dosing regimens is noteworthy from a translational standpoint, because it hints that effective renoprotection does not require aggressive dosing, a potentially valuable property given that dose-dependent toxicity is a persistent concern with many antimicrobial agents used in critically ill patients.

The one measure that resisted the treatment was glycocalyx degradation. Plasma hyaluronan, the surrogate marker of glycocalyx shedding, remained elevated in septic mice whether or not they received CSA-13, at either dose. The authors’ conclusion was measured: the administration of the ceragenin did not substantially alter hyaluronan levels in infected animals. This finding matters because it delineates the boundary of the compound’s protective reach. CSA-13 appears to safeguard kidney function and cellular structure primarily through antimicrobial and anti-inflammatory mechanisms rather than by directly preserving the endothelial glycocalyx. In practical terms, other therapeutic strategies may still be needed alongside ceragenin therapy to address the vascular barrier failure that accompanies sepsis, and future studies will need to determine whether the persistent hyaluronan elevation reflects ongoing glycocalyx damage that is functionally compensated by other protective effects.

Even with that limitation, the study carries significant implications at a moment when antimicrobial resistance is eroding the effectiveness of the clinical arsenal against Pseudomonas aeruginosa, a notoriously drug-resistant Gram-negative pathogen and a leading cause of hospital-acquired and ventilator-associated pneumonia. Previous work has demonstrated that ceragenins retain activity against multidrug-resistant clinical isolates, function in challenging biological environments such as cystic fibrosis sputum, and show promise in animal models of peritoneal, urinary tract, and intestinal infection, as well as in early clinical studies of ceragenin-coated endotracheal tubes designed to prevent ventilator-associated pneumonia. The present findings extend this evidence base by demonstrating systemic renoprotective and anti-inflammatory effects in the septic context, raising the possibility that ceragenins could one day serve as combination agents that simultaneously control infection and prevent downstream organ damage.

The researchers conclude that intraperitoneal CSA-13 administration decreases renal interleukin-6 levels and protects both kidney function and cellular integrity in pneumonia-induced sepsis, positioning the compound as a candidate component of treatment protocols aimed at preventing acute kidney injury in this setting. Much work remains before such a protocol could reach patients: the current study involved small groups of animals, a single time course, and a single sepsis model, and questions of optimal dosing, timing, safety, and efficacy relative to standard antibiotics are unresolved. Moreover, the authors acknowledge funding support from N8 Medical, Inc., a company with commercial interest in ceragenin technology, and one coauthor serves as a paid consultant, considerations that will warrant scrutiny as the work moves toward independent replication. Nevertheless, the convergence of preserved filtration markers, normalized inflammatory cytokines, and protected tissue architecture paints a coherent and encouraging picture. If subsequent studies confirm these results, ceragenins may carve out a distinctive niche in critical care medicine—molecules conceived as peptide mimics but proving their worth as protectors of the organs that sepsis strikes hardest.

The choice of cystatin C as the primary renal endpoint reflects a broader shift in nephrology toward biomarkers that detect injury earlier than creatinine. Because cystatin C is freely filtered and reabsorbed by proximal tubular cells, rising plasma concentrations can signal declining filtration before conventional tests change, making it particularly valuable in dynamic conditions such as sepsis where hours matter for intervention.

Interleukin-6 likewise carries clinical weight beyond the laboratory. Circulating IL-6 has been associated with progression to severe sepsis and mortality in critically ill patients, and the cytokine drives endothelial activation, capillary leak, and recruitment of inflammatory cells into renal tissue. The observation that kidney tissue IL-6 normalized with treatment, rather than merely declining, suggests the compound interrupted the local amplification loop rather than blunting it partially.

The persistence of elevated hyaluronan despite preserved kidney structure also raises mechanistic questions. Glycocalyx shedding is mediated by enzymes such as heparanase and hyaluronidase activated during inflammation, and their activity may outlast the cytokine surge. Alternatively, hyaluronan released from injured pulmonary tissue could contribute to circulating levels independently of renal vascular damage, a possibility that would reconcile normal histology with unchanged biomarker values.

For Pseudomonas aeruginosa specifically, the findings arrive as the pathogen appears on global watchlists of critical-priority drug-resistant bacteria. Compounds with dual antimicrobial and immunomodulatory activity could reduce reliance on high-dose beta-lactams and aminoglycosides, agents whose nephrotoxicity compounds septic renal injury. Whether ceragenins can deliver that benefit in humans will depend on pharmacokinetic studies and larger, independent animal work before clinical trials become realistic.

Subject of Research: Evaluation of the ceragenin CSA-13 for renoprotection, anti-inflammatory effects, and glycocalyx preservation in a murine model of Pseudomonas pneumonia-induced sepsis.

Article Title: CSA-13 treatment in a murine model of Pseudomonas pneumonia-induced sepsis and its effects on renal injury, inflammation, and glycocalyx derangement

Article References: Aksu, U., Bozkurt-Guzel, C., Erkose-Genc, G., Tok, O. E., Esrefoglu, M., Oyardi, O., & Savage, P. B. (2026). CSA-13 treatment in a murine model of Pseudomonas pneumonia-induced sepsis and its effects on renal injury, inflammation, and glycocalyx derangement. The Journal of Antibiotics. https://doi.org/10.1038/s41429-026-00957-5

Image Credits: AI Generated

DOI: 10.1038/s41429-026-00957-5

Keywords: ceragenin, CSA-13, sepsis, acute kidney injury, Pseudomonas aeruginosa, pneumonia, interleukin-6, cystatin C, glycocalyx, hyaluronan, antimicrobial peptides, renal inflammation