The review team, led by Deborah Doyin Alade of Elizade University in Nigeria together with colleagues at Kampala International University and Redeemer’s University, conducted a systematic literature search on January 15, 2026, across PubMed, Scopus, Web of Science, and Google Scholar. Their search terms captured cadmium alongside male reproductive system, testicular toxicity, spermatogenesis, and sperm quality. From the resulting pool, twenty studies met the inclusion criteria: five human observational studies and fifteen animal studies, fourteen of which were controlled experiments and one of which was an environmental field study. Because the studies varied enormously in design, exposure levels, duration, models, and outcome measures, the authors synthesized the data narratively rather than statistically, a choice that reflects the messy reality of toxicology across species and dose ranges.

Cadmium enters the body primarily through contaminated food, cigarette smoke, and occupational settings such as battery manufacturing, welding, and metal smelting. What makes the metal particularly insidious is its biological half-life, which can span decades in human tissue. The kidney and liver accumulate the largest burdens, but the testis is remarkably vulnerable because it lacks the robust metal-detoxifying capacity of other organs. The review emphasizes that cadmium mimics essential divalent metals such as zinc and calcium, allowing it to slip through transport channels designed for nutrients. Once inside the testis, it attacks the very structures that make sperm production possible, and it does so through several parallel mechanisms that the included studies dissected in detail.

One of the most extensively documented targets is the blood-testis barrier, a specialized junctional complex formed by Sertoli cells that shields developing germ cells from the immune system and from circulating toxins. Cadmium disrupts the tight junction proteins that hold this barrier together, causing it to become leaky. When the barrier fails, germ cells lose their protected environment, immune components can infiltrate the seminiferous tubules, and the precisely choreographed process of spermatogenesis breaks down. Animal studies in the review documented structural alterations to the seminiferous epithelium, damage to both Sertoli cells, which nurse developing sperm, and Leydig cells, which produce testosterone, and a general disorganization of testicular architecture that correlates with falling sperm counts.

The molecular engine behind much of this damage is oxidative stress. Cadmium does not directly generate reactive oxygen species the way some toxins do; instead, it cripples the cell’s antioxidant defenses, depleting glutathione and suppressing the activity of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. The resulting imbalance allows reactive oxygen species to accumulate unchecked, attacking lipids in sperm membranes, fragmenting DNA, and oxidizing proteins essential for motility. Sperm are particularly defenseless because their cytoplasm is minimal, leaving them with limited repair machinery. Several animal studies in the review measured elevated markers of lipid peroxidation alongside reduced antioxidant capacity, painting a consistent picture of redox collapse in exposed testicular tissue.

Beyond oxidative damage, the review catalogued a second lethal pathway: apoptosis, or programmed cell death. Cadmium exposure triggered the activation of caspase enzymes and shifts in the balance of Bcl-2 family proteins, tipping germ cells toward self-destruction. Mitochondrial dysfunction appears to be a central node connecting the oxidative and apoptotic cascades, since damaged mitochondria both leak reactive oxygen species and release cytochrome c, a key initiator of the apoptotic program. The studies also reported alterations in metallothionein expression, the cell’s attempt to sequester the metal, and broader molecular perturbations affecting DNA integrity. Together, these mechanisms explain how relatively low-level, chronic exposure can progressively erode sperm output without causing outright tissue necrosis.

Hormonal disruption adds another layer of complexity. The hypothalamic-pituitary-gonadal axis, which coordinates reproductive function through the pulsatile release of gonadotropin-releasing hormone, follicle-stimulating hormone, and luteinizing hormone, is sensitive to cadmium’s interference at multiple points. Studies included in the review reported changes in testosterone, FSH, and LH levels following exposure, consistent with direct toxicity to Leydig cells and indirect feedback effects from damaged seminiferous tubules. Because sperm production depends on both local testosterone concentrations within the testis and the central hormonal command system, cadmium’s dual action on the axis and on the gonads compounds its impact on fertility.

The five human observational studies generally supported the associations seen in animals, linking cadmium exposure to adverse sperm parameters and oxidative stress markers in men. However, the review is careful to note that the human evidence is not entirely consistent, and several of the studies involved potential confounding or co-exposure to other toxicants such as lead and arsenic, making it difficult to attribute observed reproductive outcomes specifically to cadmium. This is a familiar challenge in environmental epidemiology: people are rarely exposed to a single pollutant in isolation, and lifestyle factors such as smoking, which itself delivers cadmium, further complicate the picture. The authors conclude that while the human data point in the same direction as the animal work, they fall short of establishing causation on their own.

On the question of protection, the animal literature offers some grounds for cautious optimism. The review found that antioxidant supplementation, zinc administration, and various plant-derived interventions appeared to attenuate selected cadmium-associated reproductive effects in experimental models. Zinc is mechanistically plausible, since cadmium competes with zinc for binding sites and uptake pathways, and adequate zinc status may partially crowd out the toxicant. Antioxidant compounds can theoretically restore the redox balance that cadmium destroys. But the authors are emphatic that evidence for the effectiveness of these interventions in humans is limited, and no included study provided the kind of rigorous clinical trial data that would justify recommending supplements as a shield against cadmium exposure. The most reliable protection, they suggest, remains reducing exposure itself.

The review’s conclusions carry clear public health implications. Cadmium contamination of soil and food crops, particularly rice and leafy vegetables grown in polluted regions, continues in many parts of the world, and occupational exposure remains a reality for workers in metallurgy, plastics, and battery recycling. The authors call for longitudinal human studies with standardized exposure assessment, careful control of confounding factors, and deeper investigation of molecular and epigenetic mechanisms, noting that the current evidence base is dominated by animal work with heterogeneous designs. They also urge stronger efforts to reduce occupational and environmental cadmium exposure and to improve exposure monitoring. For now, the message from six years of accumulated research is that a metal most people have never thought about may be quietly working against male reproductive health, and that the scientific case for taking it seriously has never been stronger.

Subject of Research: Effects of cadmium exposure on male reproductive health, including testicular toxicity, spermatogenesis, sperm quality, and underlying molecular mechanisms

Article Title: Cadmium exposure and male reproductive health: a systematic review of mechanisms and reproductive outcomes (2020–2026)

Article References: Alade, D. D., Arogundade, A. B., Ismahil, A. A., Shehu, U. U., Ikuomola, E. O., & Abodunrin, V. K. (2026). Cadmium exposure and male reproductive health: a systematic review of mechanisms and reproductive outcomes (2020–2026). BMC Pharmacology and Toxicology. https://doi.org/10.1186/s40360-026-01248-3

Image Credits: AI Generated

DOI: 10.1186/s40360-026-01248-3

Keywords: cadmium, male reproductive health, testicular toxicity, spermatogenesis, sperm quality, oxidative stress, apoptosis, blood-testis barrier, reproductive hormones, heavy metal toxicity, environmental health, systematic review

The research, led by Huseyin Yaman and Selim Demir of the Department of Medical Biochemistry at Karadeniz Technical University in Trabzon, together with colleagues at Recep Tayyip Erdogan University, was published in BMC Complementary Medicine and Therapies. Protocatechuic acid, often abbreviated PCA, is a phenolic compound found naturally in many foods, including olives, blueberries, plums and onions, and it is also generated in the human body when larger plant polyphenols are broken down during digestion. Because it is small, readily absorbed and known to carry antioxidant activity, PCA has drawn growing interest as a possible chemopreventive agent, a compound that could be given alongside toxic drugs to protect normal tissues without weakening the anticancer effect.

To test that idea rigorously, the researchers designed a controlled experiment involving thirty adult male rats divided into five groups. One group served as a sham control, receiving no toxic challenge. A second group received protocatechuic acid alone at a dose of 100 milligrams per kilogram of body weight, to establish whether the compound had any harmful effects of its own. A third group received cisplatin at 7.5 milligrams per kilogram, delivered as a single intraperitoneal injection on the second day of the experiment, a dose calibrated to reproduce the kind of oxidative testicular injury seen clinically. The final two groups received cisplatin followed by oral protocatechuic acid at either 50 or 100 milligrams per kilogram, administered daily for seven days. This design allowed the team to compare the damage caused by cisplatin with the degree of rescue produced by two different strengths of the protective compound.

The results were striking. Cisplatin administration devastated the antioxidant defenses of the testes, producing severe lipid peroxidation, the chain-reaction destruction of the fatty membranes that surround sperm-producing cells. The researchers traced this collapse to a dramatic suppression of two master regulators of cellular redox balance: sirtuin 1, known as SIRT1, and nuclear factor erythroid 2-related factor 2, known as Nrf2. SIRT1 is a longevity-associated enzyme that maintains cellular health under stress, while Nrf2 is the transcription factor that switches on the cell’s antioxidant arsenal, including enzymes such as superoxide dismutase, glutathione peroxidase and the glutamate-cysteine ligase catalytic subunit that replenishes glutathione, the tissue’s principal internal antioxidant. When cisplatin silenced this SIRT1-Nrf2 axis, the testicular tissue was left essentially disarmed against the flood of reactive oxygen species the drug unleashes.

The damage did not stop at oxidation. The study showed that cisplatin also activated the nuclear factor kappa B pathway, a central inflammatory switch, which in turn drove elevated production of interleukin-6, a pro-inflammatory signaling molecule. At the same time, the drug triggered endoplasmic reticulum stress, a state in which the cellular organelle responsible for folding proteins becomes overwhelmed and initiates an unfolded protein response. Markers of this stress response, including binding immunoglobulin protein, activating transcription factor 6 and growth arrest and DNA damage-inducible gene 153, rose in the cisplatin-treated tissue. The final consequence was apoptosis, the programmed death of cells, confirmed both by biochemical measures of cleaved caspase-3, the executioner enzyme of cell death, and by TUNEL staining that revealed widespread DNA fragmentation in the seminiferous tubules.

Under the microscope, the toll on fertility was unmistakable. Histopathological examination using hematoxylin and eosin staining showed disorganized, damaged seminiferous tubules, the structures in which sperm are produced. Johnsen tubular biopsy scoring, a standard histological measure of testicular health, fell sharply in the cisplatin group, as did inhibin B, a hormone produced by support cells in the testes that serves as a sensitive marker of sperm-producing capacity, alongside measurable changes in testosterone. An elevated apoptotic index confirmed that a large fraction of the germ cells was dying. Together, these findings painted a complete picture of chemotherapy-induced testicular toxicity spanning oxidation, inflammation, protein-folding stress and cell death.

Protocatechuic acid reversed this cascade on nearly every front. In the rats that received the compound alongside cisplatin, the researchers documented significant improvements in oxidative stress markers, with restoration of antioxidant enzyme activity and reductions in malondialdehyde, myeloperoxidase and total oxidant status. The inflammatory NF-κB/interleukin-6 axis quieted, endoplasmic reticulum stress markers declined, and apoptotic cell death fell substantially. Most tellingly, PCA lifted the cisplatin-induced suppression of SIRT1 and Nrf2, suggesting that the compound works at least in part by reactivating the very signaling hub that chemotherapy had knocked out. Histopathology told the same story from a different angle: testicular architecture was better preserved, tubular scores improved, and TUNEL staining revealed far fewer dying cells. Both the 50 and 100 milligram per kilogram doses were effective, and the compound alone caused no observable harm.

The mechanistic story matters because it distinguishes this work from earlier, simpler antioxidant studies. Many compounds can mop up free radicals in a test tube, but the authors argue that PCA’s value lies in its modulation of upstream regulatory pathways: by preserving SIRT1 activity and allowing Nrf2 to escape repression by its inhibitor Keap1, the compound helps the tissue rebuild its own defenses rather than merely borrowing an external one. This layered action, spanning antioxidant, anti-inflammatory and anti-apoptotic arms simultaneously, is precisely what makes a candidate chemopreventive agent attractive for clinical translation, since chemotherapy toxicity is never a single-pathway problem.

The researchers emphasize that theirs is the first study to demonstrate this protective effect of protocatechuic acid against cisplatin-induced testicular toxicity, and they hypothesize that the molecule could eventually become a promising chemopreventive option for male patients undergoing cisplatin treatment, potentially preserving fertility in young cancer survivors for whom this is a lifelong concern. The team also points to the practical advantages of PCA: it is inexpensive, naturally available, orally bioavailable and already consumed safely in the diet. Still, the usual caveats apply. The findings come from a rat model with a short treatment window, and no clinical trial has yet tested PCA in human patients receiving chemotherapy. Dose, timing and possible interactions with cisplatin’s anticancer activity, a critical concern for any protective co-treatment, will all need careful evaluation before the compound can move from the laboratory bench to the oncology ward. The work was approved by the Local Animal Research Ethics Committee of Karadeniz Technical University and conducted under international animal research guidelines, and the authors declare no competing interests. As fertility preservation becomes an increasingly prominent part of cancer care, especially for adolescents and young men, simple dietary molecules that can be deployed to protect the gonads without compromising tumor treatment represent one of the most hopeful directions in supportive oncology, and this study offers a detailed molecular roadmap for exactly that ambition.

Subject of Research: Protective effects of protocatechuic acid against cisplatin-induced oxidative testicular injury in rats through modulation of redox homeostasis.

Article Title: Protocatechuic acid counteracts cisplatin-induced oxidative testicular injury in rats through modulation of redox homeostasis

Article References: Protocatechuic acid counteracts cisplatin-induced oxidative testicular injury in rats through modulation of redox homeostasis. (n.d.). https://doi.org/10.1186/s12906-026-05604-y

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05604-y

Keywords: protocatechuic acid, cisplatin, testicular toxicity, oxidative stress, SIRT1, Nrf2, NF-κB, endoplasmic reticulum stress, apoptosis, chemoprevention, infertility, rat study