Gentamicin is an aminoglycoside antibiotic used in antibacterial therapy and cell culture contamination control. Because it can induce oxidative stress, mitochondrial dysfunction, lysosomal abnormalities, apoptosis, and necrosis-like injury, gentamicin is often used to construct injury models in renal tubular epithelial cells, cochlear hair cell-like cells, and other sensitive cell types.

Keywords: gentamicin; cell injury model; nephrotoxicity; ototoxicity; oxidative stress; mitochondrial injury; apoptosis; drug toxicity evaluation

1 Research Significance of Gentamicin-Induced Cell Injury Models

1.1 Model Positioning

Gentamicin-induced cell injury models are mainly used to simulate aminoglycoside antibiotic-related cytotoxicity and are especially suitable for studying renal tubular epithelial cell injury and inner ear sensory cell injury. Compared with injury induced by strong oxidants alone, the gentamicin model is closer to drug toxicity scenarios and can reflect the continuous process of drug uptake, intracellular accumulation, oxidative stress, mitochondrial injury, and cell death.

1.2 Main Target Cells

(1) Renal tubular epithelial cells

Renal tubular epithelial cells are relatively sensitive to gentamicin, which is related to drug uptake, lysosomal accumulation, mitochondrial dysfunction, and enhanced oxidative stress. HK-2, LLC-PK1, NRK-52E, and similar cells are commonly used to simulate gentamicin-related renal tubular injury.

(2) Cochlear hair cell-like cells

Gentamicin ototoxicity is closely associated with inner ear hair cell injury. Cochlear-derived cells such as HEI-OC1 are commonly used to study auditory cell injury, ROS generation, mitochondrial function decline, and activation of apoptotic signaling.

(3) Other sensitive cells

Some hepatocytes, neurons, fibroblasts, or primary cells can also be used for gentamicin toxicity evaluation, but model interpretation should consider cell origin. Different cell types vary greatly in gentamicin uptake and tolerance, so treatment conditions from other cell lines should not be directly applied.

2 Mechanistic Basis of Gentamicin-Induced Cell Injury

2.1 Cellular Uptake and Accumulation

Gentamicin can enter cells through membrane-related transport or endocytic processes and is more likely to accumulate intracellularly in renal tubular epithelial cells. After drug accumulation, lysosomal, mitochondrial, and endoplasmic reticulum functions may be affected, causing cells to gradually progress from reversible stress to irreversible injury.

2.2 Enhanced Oxidative Stress

After gentamicin treatment, intracellular ROS levels often increase. Elevated ROS can induce lipid peroxidation, protein oxidation, and DNA damage, while disrupting antioxidant enzyme defense systems. Indicators such as SOD, CAT, GSH-Px, GSH/GSSG, MDA, and 4-HNE can be used to determine whether oxidative burden and antioxidant defense are imbalanced.

2.3 Mitochondrial Dysfunction

Mitochondria are important targets in gentamicin toxicity research. Gentamicin can induce decreased mitochondrial membrane potential, reduced ATP production, increased mitochondrial ROS, and abnormal respiratory chain function. Mitochondrial injury further promotes apoptotic signaling activation, leading to caspase activation, increased Bax/Bcl-2 ratio, and reduced cell viability.

2.4 Lysosomal and Autophagy Abnormalities

After intracellular accumulation, gentamicin can affect lysosomal stability, leading to changes in lysosomal membrane permeability and abnormal protein degradation. When autophagic flux is blocked, damaged mitochondria and oxidized proteins are insufficiently cleared, further aggravating cellular injury. LC3, p62, LAMP1, and lysosomal acidification status can be used as auxiliary evaluation indicators.

2.5 Cell Death Pathways

Gentamicin-induced cell death usually involves apoptosis, necrosis-like injury, and oxidative stress-related death. Low to moderate intensity treatment is more likely to show apoptotic features, while high-dose or prolonged treatment may cause loss of membrane integrity and increased LDH release. During model design, injury intensity should be controlled according to the research objective to avoid rapid necrosis of all cells, which would make mechanism analysis difficult.

3 Key Conditions for Model Construction

3.1 Cell Type Selection

The gentamicin injury model should prioritize cell types that match the research question. HK-2, LLC-PK1, or NRK-52E cells can be selected for nephrotoxicity research. HEI-OC1 or related hair cell-like models can be selected for ototoxicity research. Mechanistic validation can be combined with gene knockdown, overexpression, or drug-intervention cell lines.

Different cell lines differ in proliferation rate, drug uptake capacity, and antioxidant level. Preliminary experiments should be performed before formal experiments to determine the half-inhibitory range and reproducible injury window of gentamicin in the target cells.

3.2 Treatment Concentration Design

Gentamicin-induced cell injury is usually established using concentration-gradient treatment. Low concentrations can be used for mild stress and early mechanism research. Medium concentrations are suitable for establishing stable models of reduced viability and oxidative stress. High concentrations are more suitable for acute toxicity observation. Specific concentrations should be optimized according to cell type, treatment time, and detection endpoint.

A single high-dose group should not be used alone. At least a blank control, low-dose, medium-dose, and high-dose group are recommended. Cell viability, ROS, apoptosis, and injury markers should be combined to determine the optimal model condition.

3.3 Treatment Time Design

Gentamicin injury is time-dependent. Short-term treatment can reveal ROS elevation, decreased mitochondrial membrane potential, and early stress responses. Medium-duration treatment can lead to reduced cell viability, enhanced apoptotic signaling, and changes in antioxidant enzymes. Long-term treatment may cause obvious cell death and detachment.

Common time points may include 6 h, 12 h, 24 h, and 48 h. If the goal is protectant screening, treatment conditions that cause moderate injury while retaining enough viable cells are usually selected, so that the model is not too severe to observe protective effects.

3.4 Cell Density Control

Cell density significantly affects gentamicin toxicity results. When density is too low, cells are more susceptible to drug stress. When density is too high, contact inhibition, nutrient consumption, and altered effective drug exposure may affect results. Seeding density should be unified before modeling, and cell status should be consistent at the time of treatment.

4 Model Evaluation Indicators

4.1 Cell Viability and Death Evaluation

(1) Cell viability assays

CCK-8, MTT, WST-8, resazurin, and other methods can be used to evaluate changes in cellular metabolic activity after gentamicin treatment. Reduced cell viability can serve as a basic criterion for model establishment, but it cannot independently explain the injury mechanism.

(2) LDH release

LDH release reflects impaired cell membrane integrity. After high-dose or prolonged gentamicin treatment, increased LDH indicates that cells have entered an obvious injury or necrosis-like death stage.

(3) Live/dead staining

Calcein-AM/PI, trypan blue, Hoechst/PI, and similar staining methods can directly visualize the proportion of viable cells, membrane integrity, and nuclear morphology changes. These methods are suitable for use together with cell viability assays.

4.2 Oxidative Stress Indicators

(1) ROS

Probes such as DCFH-DA can be used to detect intracellular ROS levels. After gentamicin treatment, ROS elevation usually occurs before obvious cell death and is an important indicator for determining oxidative stress initiation.

(2) MDA and 4-HNE

MDA and 4-HNE reflect lipid peroxidation injury. If ROS, MDA, or 4-HNE increase simultaneously after gentamicin treatment, oxidative damage has likely expanded from the free radical level to membrane lipid injury.

(3) Antioxidant enzymes

SOD, CAT, GSH-Px, and GSH/GSSG can be used to evaluate antioxidant defense status. Under mild treatment, antioxidant enzymes may increase compensatorily, while under severe injury they may decrease or become depleted.

4.3 Mitochondrial Function Indicators

Mitochondrial membrane potential, ATP content, mitochondrial ROS, oxygen consumption rate, and mitochondrial morphology can all be used to evaluate gentamicin-related mitochondrial injury. If membrane potential decreases, ATP drops, and ROS increases, both mitochondrial energy metabolism and redox homeostasis are affected.

4.4 Apoptosis and Cell Death Pathway Indicators

Annexin V/PI, Caspase-3 activity, cleaved Caspase-3, Bax, Bcl-2, PARP cleavage, and related indicators can be used to evaluate apoptotic pathways. If gentamicin-induced cell injury is accompanied by an increased Bax/Bcl-2 ratio and caspase activation, mitochondrial-dependent apoptosis is usually involved.

4.5 Tissue-Specific Injury Indicators

In renal tubular cell models, KIM-1, NGAL, NAG, ZO-1, E-cadherin, and inflammatory factors can be evaluated. In cochlear cell models, hair cell function-related markers, mitochondrial injury, and oxidative stress indicators can be combined for analysis. Tissue-specific indicators improve model interpretation.

5 Protectant and Mechanism Validation Design

5.1 Antioxidant Protectants

N-acetylcysteine, glutathione, vitamin E, mitochondria-targeted antioxidants, and plant extracts are often used to verify the oxidative stress component in gentamicin injury. If a protectant reduces ROS, MDA, and cell death while restoring mitochondrial function, oxidative stress is likely one of the major injury mechanisms.

5.2 Mitochondrial Protection Validation

Mitochondrial protectants can be used to determine whether gentamicin toxicity depends on mitochondrial injury. Detection of membrane potential, ATP, mitochondrial ROS, and apoptotic signaling can distinguish the contributions of oxidative stress alone and mitochondrial dysfunction in the model.

5.3 Autophagy and Lysosomal Pathway Validation

Detection of LC3-II, p62, LAMP1, and lysosomal acidification status can determine whether gentamicin affects the autophagy-lysosome system. If autophagic flux is blocked and cellular injury is aggravated, this indicates reduced cellular capacity to clear damaged organelles and oxidized proteins.

5.4 Gene Intervention

Knockdown or overexpression of antioxidant enzymes, mitochondrial protective proteins, autophagy-related proteins, and drug transport-related genes can be used to clarify key regulatory links in gentamicin injury. Gene intervention experiments should be analyzed together with cell viability, ROS, and apoptosis indicators.

6 Model Applications in Different Research Scenarios

6.1 Nephrotoxicity Research

Gentamicin nephrotoxicity models focus on renal tubular epithelial cell injury. In HK-2 or LLC-PK1 cells, cell viability, ROS, MDA, mitochondrial membrane potential, KIM-1, NGAL, and apoptotic markers can be detected. If a protectant improves cell viability, oxidative stress, and renal injury markers at the same time, it may have renal tubular protective effects.

6.2 Ototoxicity Research

Gentamicin ototoxicity models are commonly used to observe oxidative injury and mitochondrial-dependent apoptosis in auditory cells. In HEI-OC1 and similar cells, ROS, mitochondrial membrane potential, Caspase-3, Bax/Bcl-2, and cell survival rate can be detected. Antioxidant or mitochondrial protectant intervention can be used to screen potential otoprotective agents.

6.3 Drug Toxicity Comparison

Gentamicin can be used as a positive injury drug to evaluate the relative cytotoxicity of different drugs or antibiotics. Such experiments should unify treatment time, cell density, and detection endpoints, and multiple indicators should be combined to avoid relying only on cell viability readings.

6.4 Antioxidant Activity Evaluation

Natural products, monomer compounds, or compound extracts can be evaluated for antioxidant protective effects using the gentamicin model. An ideal protective effect should include restored cell viability, reduced ROS, decreased MDA, improved antioxidant enzyme activity, and reduced apoptosis, rather than improvement in a single indicator only.

7 Common Problems and Optimization Directions

7.1 Insufficient Injury

If cell viability changes are not obvious after gentamicin treatment, this may be due to high cell tolerance, insufficient drug concentration, too short treatment time, or excessive cell density. The model can be optimized by increasing the concentration gradient, prolonging treatment time, or reducing seeding density.

7.2 Excessive Cell Death

High-dose or long-term treatment may cause rapid cell detachment and necrosis-like death. In this case, gentamicin concentration should be reduced, treatment time should be shortened, or earlier time points should be selected to detect ROS, mitochondrial function, and apoptosis indicators.

7.3 Poor Reproducibility

Poor reproducibility is often related to inconsistent cell condition, seeding density, drug preparation, medium batch, and dosing time. Gentamicin working solution should be prepared according to experimental requirements and repeated freeze-thaw cycles should be avoided. Cells should be in stable condition before treatment.

7.4 Unstable Protectant Effects

Unstable protectant effects may result from insufficient pretreatment time, inappropriate concentration selection, excessive model injury, or detection system interference. Pretreatment, co-treatment, and post-treatment modes can be set to clarify the stage at which the protectant acts.

8 Reagent Selection for Gentamicin Cell Injury Models

8.1 Reagents Related to Model Construction and Mechanistic Research of Gentamicin-Induced Cell Injury Models

8.2 Selection of Detection Reagents Related to Injury Evaluation in Gentamicin-Induced Cell Injury Models

Gentamicin-induced cell injury models are suitable for drug toxicity, nephrotoxicity, ototoxicity, and oxidative stress protection research. During model construction, concentration and time should be optimized according to cell type. A moderate, reproducible injury window should be prioritized, and cell viability, oxidative stress, mitochondrial function, and apoptosis indicators should be combined for comprehensive evaluation.

For more related articles, please see below:

[1] Oxidative Stress and Experimental Interpretation Framework for ROS, JC-1, MPTP, and Calcium Indicators in Mitochondrial Function Assessment