Preventive effects of nerve growth factor against colistin-induced autophagy and apoptosis in PC12 cells

Colistin Induces Oxidative Stress and Apoptotic Cell Death through the Activation of the AhR/CYP1A1 Pathway in PC12 Cells

Colistin is commonly regarded as the "last-resort" antibiotic for combating life-threatening infections caused by multidrug-resistant (MDR) gram-negative bacteria. Neurotoxicity is a potential adverse event associated with colistin application in clinical settings, yet the exact molecular mechanisms remain unclear. This study examined the detrimental impact of colistin exposure on PC12 cells and the associated molecular mechanisms. Colistin treatment at concentrations of 0-400 μM decreased cell viability and induced apoptotic cell death in both time- and concentration-dependent manners. Exposure to colistin triggered the production of reactive oxygen species (ROS) and caused oxidative stress damage in PC12 cells. N-acetylcysteine (NAC) supplementation partially mitigated the cytotoxic and apoptotic outcomes of colistin. Evidence of mitochondrial dysfunction was observed through the dissipation of membrane potential. Additionally, colistin treatment upregulated the expression of AhR and CYP1A1 mRNAs in PC12 cells. Pharmacological inhibition of AhR (e.g., using α-naphthoflavone) or intervention with the CYP1A1 gene significantly decreased the production of ROS induced by colistin, subsequently lowering caspase activation and cell apoptosis. In conclusion, our findings demonstrate, for the first time, that the activation of the AhR/CYP1A1 pathway contributes partially to colistin-induced oxidative stress and apoptosis, offering insights into the cytotoxic effects of colistin.

Prevention of colistin-induced neurotoxicity: a narrative review of preclinical data

Polymyxin E or colistin is an effective antibiotic against MDR Gram-negative bacteria. Due to unwanted side effects, the use of this antibiotic has been limited for a long time, but in recent years, the widespread of MDR Gram-negative bacteria infections has led to its reintroduction. Neurotoxicity and nephrotoxicity are the significant dose-limiting adverse effects of colistin. Several agents with anti-inflammatory and antioxidant properties have been used for the prevention of colistin-induced neurotoxicity. This study aims to review the preclinical studies in this field to prepare guidance for future human studies. The data was achieved by searching PubMed, Scopus, and Google Scholar databases. All eligible pre-clinical studies performed on neuroprotective agents against colistin-induced neurotoxicity, which were published up to September 2023, were included. Finally, 16 studies (ten in vitro and eight in vivo) are reviewed. Apoptosis (in 13 studies), inflammatory (in four studies), and oxidative stress (in 14 studies) pathways are the most commonly reported pathways involved in colistin-induced neurotoxicity. The assessed compounds include non-herbal (e.g., ascorbic acid, rapamycin, and minocycline) and herbal (e.g., curcumin, rutin, baicalein, salidroside, and ginsenoside) agents. Besides these compounds, some other measures like transplantation of mitochondria and the use of nerve growth factor and mesenchymal stem cells could be motivating subjects for future research. Based on the data from experimental (in vitro and animal) studies, a combination of colistin with neuroprotective agents could prevent or decrease colistin-induced neurotoxicity. However, well-designed randomized clinical trials and human studies are essential for demonstrating efficacy.

The potential role of Tirzepatide as adjuvant therapy in countering colistin-induced nephro and neurotoxicity in rats via modulation of PI3K/p-Akt/GSK3-β/NF-kB p65 hub, shielding against oxidative and endoplasmic reticulum stress, and activation of p-CREB/BDNF/TrkB cascade

Although colistin has a crucial antibacterial activity in treating multidrug-resistant gram-negative bacteria strains; it exhibited renal and neuronal toxicities rendering its use a challenge. Previous studies investigated the incretin hormones either glucose-dependent insulinotropic polypeptide (GIP) or glucagonlike peptide-1 (GLP-1) for their neuroprotective and nephroprotective effectiveness. The present study focused on investigating Tirzepatide (Tirze), a dual GLP-1/GIP agonist, as an adjuvant therapy in the colistin treatment protocol for attenuating its renal and neuronal complications. Rats were divided into; The normal control group, the colistin-treated group received colistin (300,000 IU/kg/day for 7 days; i.p.). The Tirze-treated group received Tirze (1.35 mg/kg on the 1,4,7thdays; s.c.) and daily colistin. Tirze effectively enhanced histopathological alterations, renal function parameters, and locomotor activity in rats. Tirze mechanistically acted via modulating various signaling axes evolved under the insult of phosphatidylinositol 3-kinases (PI3K)/phosphorylated protein kinase-B (p-Akt)/ glycogen synthase kinase (GSK)3-β hub causing mitigation of nuclear factor (NF)-κB (NF-κB) / tumor necrosis factor-α (TNF-α), increment of nuclear factor erythroid 2-related factor 2 (Nrf2)/ glutathione (GSH), downregulation of ER stress-related biomarkers (activation transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP)), antiapoptotic effects coupling with reduction of glial fibrillary acidic protein (GFAP) immunoreactivity and enhancement of phosphorylated c-AMP response element-binding (p-CREB) / brain-derived neurotrophic factor (BDNF)/tyrosine kinase B (TrkB) neuroprotective pathway. Briefly, Tirze exerts a promising role as adjuvant therapy in the colistin treatment protocol for protection against colistin's nephro- and neurotoxicity according to its anti-inflammatory, antioxidant, and antiapoptotic impacts besides its ability to suppress ER stress-related biomarkers.

Nerve Growth Factor Confers Neuroprotection against Colistin-Induced Peripheral Neurotoxicity

Neurotoxicity is an unwanted side effect for patients when receiving parenteral colistin therapy. The development of effective neuroprotective agents that can be coadministered during colistin therapy remains a priority area in antimicrobial chemotherapy. The present study aimed to investigate the protective effect of nerve growth factor (NGF) against colistin-induced peripheral neurotoxicity using a murine model. C57BL/6 mice were randomly divided into the following 6 groups: (i) untreated control, (ii) NGF alone (36 μg/kg/day administered intraperitoneally), (iii) colistin alone (18 mg/kg/day administered intraperitoneally), and (iv-vi) colistin (18 mg/kg/day) plus NGF (9, 18, and 36 μg/kg/day). After treatment for 7 days, neurobehavioral and electrophysiology changes, histopathological assessments of sciatic nerve damage, and oxidative stress biomarkers were examined. The mRNA expression levels of Nrf2, HO-1, Akt, Bax, and caspase-3 and -9 were assessed using quantitative RT-PCR. The results showed that, across all the groups wherein NGF was coadministered with colistin, a marked attenuation of colistin-induced sciatic nerve damage and improved sensory and motor function were observed. In comparison to the colistin only treatment group, animals that received NGF displayed upregulated Nrf2 and HO-1 mRNA expression levels and downregulated Bax and caspase-3 and -9 mRNA expression levels. In summary, our study reveals that NGF coadministration protects against colistin-induced peripheral neurotoxicity via the activation of Akt and Nrf2/HO-1 pathways and inhibition of oxidative stress. This study highlights the potential clinical application of NGF as a neuroprotective agent for coadministration during colistin therapy.

Polymyxins-Curcumin Combination Antimicrobial Therapy: Safety Implications and Efficacy for Infection Treatment

The emergence of antimicrobial resistance in Gram-negative bacteria poses a huge health challenge. The therapeutic use of polymyxins (i.e., colistin and polymyxin B) is commonplace due to high efficacy and limiting treatment options for multidrug-resistant Gram-negative bacterial infections. Nephrotoxicity and neurotoxicity are the major dose-limiting factors that limit the therapeutic window of polymyxins; nephrotoxicity is a complication in up to ~60% of patients. The emergence of polymyxin-resistant strains or polymyxin heteroresistance is also a limiting factor. These caveats have catalyzed the search for polymyxin combinations that synergistically kill polymyxin-susceptible and resistant organisms and/or minimize the unwanted side effects. Curcumin—an FDA-approved natural product—exerts many pharmacological activities. Recent studies showed that polymyxins–curcumin combinations showed a synergistically inhibitory effect on the growth of bacteria (e.g., Gram-positive and Gram-negative bacteria) in vitro. Moreover, curcumin co-administration ameliorated colistin-induced nephrotoxicity and neurotoxicity by inhibiting oxidative stress, mitochondrial dysfunction, inflammation and apoptosis. In this review, we summarize the current knowledge-base of polymyxins–curcumin combination therapy and discuss the underlying mechanisms. For the clinical translation of this combination to become a reality, further research is required to develop novel polymyxins–curcumin formulations with optimized pharmacokinetics and dosage regimens.

Curcumin Attenuates Colistin-Induced Peripheral Neurotoxicity in Mice

Peripheral neurotoxicity often occurs in patients receiving parenteral polymyxin therapy (i.e., colistin methanesulfonate or polymyxin B). The present study aimed to investigate the protective effect of curcumin on colistin-induced peripheral neurotoxicity using a murine model. Female C57BL/6 mice (n = 10 in each group) were randomly divided into the following: (1) control group (saline), (2) curcumin only group (200 mg/kg/day; orally), (3) colistin only group (18 mg/kg/day; i.p.), (4) colistin (18 mg/kg/day) plus curcumin 50 mg/kg/day group, (5) colistin (18 mg/kg/day) plus curcumin 100 mg/kg/day group, (6) colistin (18 mg/kg/day) plus curcumin 200 mg/kg/day group; all mice were treated for 7 days. Orally applied curcumin was detected in the brain, cerebellum, and sciatic nerve. Co-administration of oral curcumin markedly improved colistin-induced impaired sensory and motor dysfunctions in a dose-dependent manner. Curcumin supplementation at 100 and 200 mg/kg significantly decreased lipid peroxidation and upregulated catalase (CAT) and superoxide dismutase (SOD) activities, ATP levels, and Na⁺/K⁺-ATPase activity in sciatic nerve tissue, compared to the colistin alone group. Curcumin supplementation at 200 mg/kg upregulated the levels of AKT, NGF, mTOR, Nrf2, and HO-1 mRNA and concomitantly downregulated Bax, caspases-3, and -9 mRNA; it also decreased caspase-3 and caspase-9 activity. In summary, for the first time, our study reveals that the protective effect of oral curcumin on colistin induced peripheral neurotoxicity is associated with the activation of NGF/Akt and Nrf2/HO-1 pathways and inhibition of oxidative stress. This study highlights the potential clinical application of curcumin as an oral neuroprotective agent coadministered during colistin therapy.