Comparative Protective Effects of Melatonin and Apigenin Against Paclitaxel-Induced Testicular Injury in Rats: Oxidative Stress, DNA Damage, Apoptosis, and NF-κB Signaling

Melatonin and apigenin each partially reversed paclitaxel-induced testicular damage in rats, raising Johnsen scores from 5 back to ~8 out of 9

Journal: Nutrients | Published: 2026-05-21 | Type: Animal study, comparative | PMID: 42197101 Authors: Saydam F et al. — all from Recep Tayyip Erdogan University, Rize, Türkiye Funding/COI: Recep Tayyip Erdogan University Development Foundation, Scientific Research Projects Unit, and TUBITAK (Turkish national science council). No conflicts of interest declared.

Summary

Paclitaxel, a taxane chemotherapeutic, is well-documented to damage testicular tissue through oxidative stress, inflammation, and apoptosis. This rat study compared melatonin (10 mg/kg) and apigenin (a flavonoid found in parsley and chamomile, 27 mg/kg) as co-administered protective agents, both given 30 minutes before each weekly paclitaxel dose. Both compounds partially restored testicular architecture. Apigenin showed an odd wrinkle: it lowered glutathione (an antioxidant) under normal conditions but raised it in paclitaxel-damaged tissue — a context-dependent effect the authors flag but don't fully explain.

Claims

• Paclitaxel (5 mg/kg IP, weekly × 4) reduced Johnsen spermatogenesis scores from 9 (9–9) in controls to 5 (4–6)
• Paclitaxel significantly elevated MDA (lipid peroxidation marker) vs. saline control (p=0.006) and decreased GSH (antioxidant) (p<0.001)
• Paclitaxel increased caspase-3 immunoreactivity (apoptosis), 8-OHdG (oxidative DNA damage), and NF-κB/p65 (inflammatory signaling)
• Melatonin co-administration reduced MDA vs. paclitaxel alone (p=0.001), restored GSH (p<0.001), and improved Johnsen score to 8 (7–9)
• Apigenin co-administration reduced MDA vs. DMSO control (p=0.001), raised GSH vs. paclitaxel alone (p=0.005), and improved Johnsen score to 8 (8–8)
• Apigenin alone reduced GSH vs. DMSO control (p<0.001) without causing histological damage — authors interpret this as context-dependent redox modulation
• Both agents reduced caspase-3, 8-OHdG, and NF-κB/p65 immunoreactivity compared to paclitaxel alone

Study Quality

Eight rats per group, seven groups (n=56 total) — this is a small animal study with no human applicability established. The seven-group design is reasonable and includes proper solvent controls: DMSO was used to dissolve apigenin, so a separate DMSO-only group was included. This matters because DMSO has its own biological activity, and the authors note that DMSO and paclitaxel groups showed comparable MDA levels, complicating some comparisons. The study followed ARRIVE 2.0 animal reporting guidelines and received ethics committee approval. Multiple mechanistic endpoints were measured (biochemical, immunohistochemical, histological), which adds mechanistic depth but also multiplies the risk of false positives without correction for multiple comparisons — the paper does not report any such correction.

Critically, no functional reproductive outcomes were assessed. Johnsen scores measure spermatogenic integrity histologically, but the study did not measure sperm count, motility, morphology, or actual fertility. The gap between "seminiferous tubules look better under the microscope" and "this animal can reproduce" is real and unaddressed.

Red Flags

• n=8 per group; underpowered for definitive conclusions, and no power calculation is reported
• No functional fertility endpoints — no sperm parameters, no breeding outcomes
• All findings are correlative; the paper explicitly cautions that causal relationships between NF-κB, caspase-3, and 8-OHdG were not established
• Apigenin's GSH-lowering effect under basal conditions is unexplained and potentially concerning at higher doses or different contexts — the authors acknowledge it without resolving it
• Published in Nutrients, a nutrition journal, rather than a reproductive biology or urology journal — lower bar for animal mechanistic studies
• No dose-response data for either protective agent; the doses chosen are pharmacological, not dietary
• Human translation is entirely speculative; pharmacokinetics, bioavailability, and appropriate dosing in people are unknown

Strengths

• Seven groups including both saline and DMSO solvent controls, head-to-head comparison of two agents
• Multiple mechanistic endpoints spanning oxidative, apoptotic, inflammatory, and structural domains
• Standardized Johnsen scoring by trained histologists
• ARRIVE 2.0 compliance
• Acknowledges limitations including correlative nature of findings and absence of functional outcomes
• No industry funding; no conflicts of interest

Verdict

This is competent rat-model mechanistic work with a sensible design — it clearly shows that paclitaxel damages rat testes through oxidative and apoptotic pathways, and that melatonin and apigenin attenuate those markers. But it proves nothing about human fertility preservation during chemotherapy. The sample size is small, functional sperm parameters were never measured, and no causal pathway was established. The apigenin GSH paradox is a genuine scientific curiosity that deserves follow-up, not a clinical signal. File this as a rodent proof-of-concept that motivates further mechanistic work, not as evidence that cancer patients should take melatonin supplements during chemotherapy.