Deciphering ciprofloxacin-induced neurotoxicity: behavioral and molecular profiling of ciprofloxacin treatment in rats

Abstract

Introduction: Ciprofloxacin is a fluoroquinolone antibiotic commonly used to treat various bacterial infections, with a potential to induce adverse mood effects in patients. Since the molecular mechanism of ciprofloxacin-induced neurotoxicity is poorly understood, we aimed to identify behavioral changes and corresponding neurotransmitter pattern after its prolonged administration in rats. We screened for untoward effects of ciprofloxacin on locomotor activity, despair, anhedonia, object recognition memory, and anxiety, as behavioral domains affected in various psychiatric diseases. Methodology: Three-month old male Sprague-Dawley rats were orally gavaged with ciprofloxacin (20 or 100 mg/kg) or solvent (0.5% methyl cellulose solution) each day for 4 weeks (n=80). One group of animals (n=40) passed the open field (OF), novel object recognition test (NORT), and forced swimming test (FST). Another group (n=40) underwent elevated plus maze (EPM) and sucrose preference test (SPT). After the completion of behavioral battery, the prefrontal cortex and cerebrospinal fluid (CSF) were collected. The neurotransmitters and metabolites of the kynurenine pathway were determined in the prefrontal cortex (PFC) through HPLC-MS/MS. Additionally, levels of interleukin-2 (IL-2) in CSF were quantified with Luminex. Behavioral and molecular parameters were analyzed by one-way ANOVA followed by Dunnett post hoc test in GraphPad Prism 9. Results: In FST, the treatment with high dose of ciprofloxacin decreased the swim time compared to control, which could be related to induction of despair-like behavior (p<0.05). The ciprofloxacin treatment did not affect object memory in NORT. In OF, the distance travelled and the number of rotations were not changed after treatment with ciprofloxacin compared to the control group. Further, animals treated with ciprofloxacin did not show changes in parameters in EPM and SPT. The acetylcholine levels in PFC were increased after ciprofloxacin treatment (p<0.05) in comparison with controls, which could be associated with depressed mood states. In line with that, high dose of ciprofloxacin treatment showed the tendency to decrease and increase levels of GABA and dopamine, respectively, but without reaching the statistical significance (p=0.07 and p=0.06). No changes in kynurenine pathway were observed after the treatment. The IL-2 concentration in CSF was increased after prolonged administration of low dose of ciprofloxacin treatment compared to the control levels (p<0.05), which could imply immunological stimulation of T lymphocytes and potential neuroinflammation. Conclusion: The despair behavior after treatment with high dose of ciprofloxacin was accompanied by increased levels of acetylcholine in PFC. Furthermore, the high dose of ciprofloxacin treatment showed tendency to decrease GABA levels, and increase dopamine levels in PFC, which could be connected to psychiatric adverse effects. Nonetheless, further studies are essential to confirm these neurotransmitter changes. On the other hand, the low dose of ciprofloxacin treatment elicited the increase of IL-2, which could be a marker of neuroinflammation-related neurotoxicity. In the future, efforts should be made to examine the role of IL-2 in the interaction of the immune system and the central nervous system, as its potential significance as a biomarker.