The research team, based at the University of Texas Medical Branch, enrolled sixteen adults between the ages of 50 and 60 in a randomized, double-blind crossover trial. Each participant took sildenafil at 50 milligrams per day or tadalafil at 10 milligrams per day for four weeks, along with a visually identical placebo for another four weeks, in an order determined by random assignment. Neither the volunteers nor the investigators knew which pill was being taken at any point. The crossover design meant that every participant served as their own control, allowing the researchers to compare molecular measurements taken before drug exposure with those taken after a month of active treatment within the same person, a powerful approach for filtering out individual biological noise.

What set this study apart was the sheer breadth of molecular sampling. At each study visit, participants provided fasting blood samples and underwent needle biopsies of the vastus lateralis, the large quadriceps muscle on the side of the thigh. Those tissue and blood samples were then subjected to four complementary analytical approaches: transcriptomics to measure gene activity, proteomics to quantify the proteins actually being produced, metabolomics to track lipid signaling molecules and amino acid pathways in plasma, and immunohistochemistry to count inflammatory immune cells embedded in the muscle. The researchers also used liquid chromatography-tandem mass spectrometry to verify that participants had genuine drug in their bloodstream, confirming that sildenafil and tadalafil concentrations fell within ranges previously reported for these doses.

The most consistent signal emerged from the blood. After four weeks of treatment with either drug, levels of eicosanoids, bioactive lipid messengers derived from polyunsaturated fatty acids, shifted in a direction associated with reduced inflammation. Sildenafil treatment lowered 12-hydroxyeicosatetraenoic acid, a product of the 12-lipoxygenase enzyme that has been linked to oxidative stress, endothelial dysfunction, neuroinflammation, and cancer metastasis, and also reduced 5-HETE, a related mediator implicated in tumor progression and Alzheimer’s disease. Tadalafil produced similar reductions in 12-HETE and 13-HODE, another lipid mediator associated with cognitive impairment, while simultaneously raising levels of protectin D1, an anti-inflammatory docosanoid derived from docosahexaenoic acid that is known to be produced by macrophages at sites of tissue injury.

Both drugs also appeared to rev up the body’s arginine biosynthesis machinery. Sildenafil increased plasma L-arginine by roughly 1.55-fold, while tadalafil raised citrulline and argininosuccinate, two intermediates of the citrulline-nitric oxide cycle that feeds the raw material for nitric oxide production. The authors propose several possible explanations: the drugs may suppress arginase, an enzyme that competes with nitric oxide synthase for arginine; they may dial down inducible nitric oxide synthase, the inflammatory form of the enzyme; or they may improve the health of small intestinal enterocytes, the cells responsible for manufacturing citrulline in the first place. Whatever the mechanism, the shift suggests these drugs do not merely prolong nitric oxide signaling but may actively expand the substrate supply that fuels it.

Inside the muscle, the two drugs told strikingly different stories. Sildenafil produced a broad transcriptional response, with 101 genes upregulated and 23 downregulated after four weeks. The enriched gene ontology terms clustered around cell adhesion, cell motility, immune system processes, extracellular matrix organization, and blood vessel and bone development, patterns that the authors note resemble the molecular signature of long-term aerobic exercise training. Proteomic analysis reinforced this picture: 136 proteins increased after sildenafil treatment, including components of the protein folding machinery that govern the unfolded protein response, a cellular quality-control system also activated during exercise adaptation. Notably, proteins involved in telomere maintenance and DNA biosynthesis also rose, hinting at possible effects on cellular aging, since telomere length in skeletal muscle is positively associated with physical activity and inversely related to age-related disease.

Tadalafil, despite remaining active in the body far longer than sildenafil, left almost no coherent mark on the muscle transcriptome, with no differentially expressed genes detected at all, and produced a proteomic response dominated by downregulated proteins with few shared functional themes. The researchers find this asymmetry puzzling and raise the possibility that some of sildenafil’s muscular effects may be off-target. The two drugs are structurally dissimilar and cross-react with other phosphodiesterase enzymes to different degrees: sildenafil inhibits PDE-1 and PDE-6 more strongly, while tadalafil inhibits PDE-11, an enzyme found in skeletal muscle whose physiological role remains poorly understood. The discrepancy underscores how little is still known about why these chemically distinct molecules diverge once they leave the bloodstream.

To weave the three omics layers together, the team applied a multiblock statistical integration method called DIABLO, which selects the variables from each dataset that best discriminate between pre- and post-treatment states. For the sildenafil group, the most influential gene was SPTLC2, a subunit of the enzyme that initiates sphingolipid biosynthesis and has been linked to both aging and exercise adaptation; the most influential protein was PHKA1, a regulator of glycogen breakdown whose reduction could reflect the drugs’ known ability to enhance muscle glucose uptake; and the top metabolite was L-arginine itself. For tadalafil, the leading gene was MCUB, a negative regulator of the mitochondrial calcium uniporter whose downregulation could theoretically increase mitochondrial calcium uptake, a change associated with muscle hypertrophy in animal models and reduced by aging.

Not every result supported the repurposing enthusiasm. Immunohistochemical counts of M1 and M2 macrophages in the muscle biopsies showed no significant change with either drug, meaning the systemic anti-inflammatory signal in the blood was not mirrored by a measurable shift in the local immune environment of the tissue. The authors caution that repeated biopsies taken close to previous sampling sites may have introduced local inflammation that obscured treatment effects, and they acknowledge that the small sample size of eight participants per drug group limits statistical power. Functional measures of strength, endurance, and self-reported fatigue likewise showed no significant improvement over the four-week window, despite earlier work from the same group showing that just eight days of sildenafil increased muscle protein synthesis in healthy men.

Even with those caveats, the study offers a compelling molecular map of what these widely prescribed drugs do beyond their famous vascular effects. The convergence of reduced pro-inflammatory lipid mediators, elevated arginine pathway substrates, and exercise-like gene expression patterns in muscle provides testable hypotheses for future trials targeting inflammation, sarcopenia, cognitive decline, and cancer-related fatigue. The authors call for larger studies with careful attention to sampling techniques and longer treatment durations to determine whether the molecular shifts documented here translate into meaningful clinical benefits for the growing population of healthy adults hoping to age well.

Subject of Research: Multi-omics analysis of the systemic and skeletal muscle effects of PDE-5 inhibitors in healthy middle-aged adults

Article Title: Assessing the therapeutic potential of PDE‐5 inhibitors in adults: Insights from a multi‐omics study

Article References: McGovern, K. A., Wright, T. J., Marchant, E. D., Kilroe, S. P., Durham, W. J., Dillon, E. L., Baum, M. M., Kinsky, M. P., Russell, W. K., Fry, C. S., Gongloor, P., Pyles, R. B., Urban, R. J., Rasmussen, B. B., & Sheffield‐Moore, M. (2026). Assessing the therapeutic potential of PDE ‐5 inhibitors in adults: Insights from a multi‐omics study. Physiological Reports, 14(18), Article e71104. https://doi.org/10.14814/phy2.71104

Image Credits: AI Generated

DOI: 10.14814/phy2.71104

Keywords: PDE-5 inhibitors, sildenafil, tadalafil, multi-omics, inflammation, eicosanoids, skeletal muscle, arginine biosynthesis, proteomics, transcriptomics, metabolomics, drug repurposing

The review, authored by Joanna Kirmuć and Karol Kramkowski of the Medical University of Białystok together with gynecologic oncologist Marcin Jóźwik, synthesizes evidence connecting oxidative stress, chronic inflammation, and platelet activation with ovarian cancer progression. Its central thesis is that platelet-derived lipid messengers, particularly thromboxane B2, the stable metabolite of the potent platelet aggregator thromboxane A2, deserve systematic investigation as biomarkers that could complement the flawed diagnostic tools currently in clinical use. The authors are careful to stress that the clinical utility of these molecules remains unproven, but they make a compelling mechanistic case for why the field should pay attention.

To understand the argument, it helps to grasp why existing diagnostics fall short. The workhorses of ovarian cancer detection are two proteins, CA125 and HE4, often combined with menopausal status in the Risk of Ovarian Malignancy Algorithm, or ROMA. CA125, a mucin known as MUC16, rises above the conventional threshold of 35 units per milliliter in many epithelial ovarian cancers, but it also climbs during menstruation, pregnancy, endometriosis, inflammatory bowel disease, and unrelated malignancies. HE4, encoded by the WFDC2 gene, is more specific and elevated across all disease stages, yet its performance varies by histological subtype. ROMA improves specificity over either marker alone, but it cannot reliably gauge tumor aggressiveness or detect metastases, and neither marker nor any combination of them has proven accurate enough for population-level screening.

The stakes of this diagnostic gap are enormous. Stage I ovarian cancer carries cure rates of up to 90 percent, yet only about 20 percent of cases are caught that early. Large randomized screening trials, including the UK Collaborative Trial of Ovarian Cancer Screening and the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, tested multimodal strategies combining ultrasound, longitudinal CA125 algorithms, and emerging molecular markers, and none demonstrated a meaningful reduction in mortality. Ultrasound is operator-dependent and can miss early lesions, while CA125 lacks the specificity needed to distinguish cancer from benign inflammation. The field, in short, needs biomarkers that capture the dynamic biology of the tumor rather than merely its bulk.

This is where platelets enter the picture. Cancer and coagulation are deeply intertwined. Tumor cells express tissue factor, shed tissue factor-positive extracellular vesicles, and activate the coagulation cascade to generate thrombin. Thrombin then activates platelets through protease-activated receptors, triggering phospholipase A2, the release of arachidonic acid from membrane phospholipids, and the cyclooxygenase-1-dependent synthesis of thromboxane A2, which is rapidly hydrolyzed to measurable thromboxane B2. Experimental studies in ovarian cancer have shown that platelet-tumor cell interactions enhance tissue factor expression, promote metastatic cell phenotypes, and drive cancer cell migration. Activated platelets form aggregates with tumor cells, creating a protective shield that facilitates immune evasion and dissemination, with receptors such as glycoprotein VI and C-type lectin-like receptor 2 mediating recognition of matrix components and podoplanin-expressing tumor cells.

The eicosanoid system that platelets draw upon is a sprawling lipid signaling network with three main branches. Arachidonic acid released by phospholipase A2 is metabolized through cyclooxygenase, lipoxygenase, and cytochrome P450 pathways, yielding prostaglandins, thromboxanes, hydroxyeicosatetraenoic acids, and other mediators. In cancer, this network tilts toward tumor promotion. Thromboxane A2 and prostaglandin E2 drive pro-tumor signaling, while lipoxygenase-derived HETEs such as 12-HETE and 15-HETE are associated with inflammation, invasion, and tumor progression. Meanwhile, prostacyclin, produced mainly by vascular cells, exerts opposing vasodilatory and anti-aggregatory effects, and the balance between thromboxane A2 and prostacyclin is pivotal for vascular homeostasis. In cancer and chronic inflammation, platelet activity often becomes excessive, disrupting that balance and potentially fueling angiogenesis and metastatic spread.

Oxidative stress provides a further mechanistic thread linking these pathways. Reactive oxygen species damage DNA, proteins, and lipids, promoting genomic instability, but they also activate phospholipase A2 directly, increasing arachidonic acid release and amplifying thromboxane synthesis within platelets. Cancer cells adapt by bolstering antioxidant defenses and co-opting redox-sensitive signaling cascades such as MAPK, JNK, and NF-kappaB to enhance survival and proliferation. Chronic pelvic inflammation, including the inflammatory-like event of ovulation itself with its bursts of chemokines, growth factors, and reactive oxygen species, may contribute to repeated carcinogenic exposure. Cytokines such as interleukin 6, tumor necrosis factor alpha, and interleukin 8 promote tumor growth, immune evasion, and therapeutic resistance, and elevated interleukin 6 correlates with advanced disease and poorer outcomes. Inflammation also enhances platelet activation and thromboxane biosynthesis, closing the loop between the tumor microenvironment and platelet-derived eicosanoids.

What does the actual clinical evidence on thromboxane B2 in ovarian cancer show? Early studies from the 1980s reported elevated thromboxane B2 levels in patients with gynecological malignancies, and in-vitro work suggested that a predominance of thromboxane A2 may contribute to tumor growth and dissemination. One study found thromboxane B2 levels significantly higher in metastatic ovarian cancer tissue than in localized tumors, borderline malignant tumors, benign lesions, or normal tissue. Evidence from colorectal and lung adenocarcinoma supports the biological relevance of thromboxane metabolites in cancer-associated platelet activation, and a substudy of the Add-Aspirin trial linked 11-dehydro-thromboxane B2 levels to tumor characteristics in gastrointestinal cancers. Yet the ovarian data are decades old, were never systematically stratified by FIGO stage, histological subtype, treatment response, or survival, and never established sensitivity, specificity, AUC values, or validated cut-offs. The authors identify this as a striking knowledge gap: no recent studies from the past two decades have specifically investigated eicosanoid profiles in ovarian cancer patients.

Measurement technology, however, has advanced considerably. Thromboxane B2 can be quantified by enzyme-linked immunosorbent assay, gas chromatography, or high-performance liquid chromatography, but liquid chromatography-mass spectrometry is increasingly preferred because it simultaneously quantifies multiple eicosanoids with high precision from small sample volumes of plasma or urine, enabling minimally invasive sampling. Recent lipidomic studies have identified distinct circulating lipid signatures in ovarian cancer patients, with alterations in phospholipids, ceramides, sphingomyelins, and triacylglycerols detectable even in early-stage disease. The authors propose that a multiplex panel integrating CA125, HE4, and selected platelet- and inflammation-derived lipid mediators, including thromboxane B2, prostacyclin metabolites, and lipoxygenase-derived HETEs, could improve discrimination between benign inflammatory conditions and early-stage epithelial ovarian cancer while offering insight into tumor aggressiveness that conventional markers cannot provide.

There are important caveats, and the review does not shy away from them. Thromboxane B2 is not cancer-specific; it reflects thromboxane biosynthesis from any source, including inflammatory cells, and must be interpreted as a marker of platelet activation rather than of malignancy itself. Routine implementation of LC-MS eicosanoid profiling faces hurdles of instrumentation cost, specialized infrastructure, and the absence of standardized analytical protocols. Intriguingly, the platelet connection also has therapeutic implications: epidemiological evidence suggests regular aspirin use, which irreversibly inhibits platelet COX-1, may modestly reduce ovarian cancer risk, though the evidence remains insufficient to recommend aspirin for primary prevention. The authors call for prospective studies in adequately powered cohorts spanning healthy individuals, benign gynecological conditions, and diverse ovarian cancer stages and subtypes, with standardized procedures and clinically relevant cut-off values. If those studies succeed, the humble platelet, long a bit player in oncology, could become a central informant in detecting one of medicine’s deadliest cancers before it is too late.

Subject of Research: Platelet activation and eicosanoid signaling as potential biomarkers in ovarian cancer

Article Title: Platelet activation and eicosanoid signaling in ovarian cancer: implications for biomarker development

Article References: Kirmuć, J., Jóźwik, M., & Kramkowski, K. (2026). Platelet activation and eicosanoid signaling in ovarian cancer: implications for biomarker development. Molecular Biology Reports, 53(1), Article 1664. https://doi.org/10.1007/s11033-026-12848-x

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12848-x

Keywords: ovarian cancer, platelets, thromboxane B2, eicosanoids, biomarkers, CA125, HE4, ROMA algorithm, oxidative stress, inflammation, lipidomics, early detection