Antioxidants

Although oxidants are known to be deleterious for cellular homeostasis by oxidizing macromolecules like DNA or proteins, they are also involved in signaling processes essential for cellular proliferation and survival. Here, we investigated the role of superoxide anion (O₂⁻) and hydrogen peroxide (H₂O₂) homeostasis for the proliferation and survival of classical Hodgkin’s lymphoma (cHL) cell lines. Inhibition of NADPH oxidases (NOX) using apocynin (Apo) and diphenylene iodonium (DPI), or treatment with the antioxidant butylated hydroxyanisole (BHA), significantly reduced proliferation and induced apoptosis in HL cell lines. These effects correlated with transcriptomic alterations involving redox regulation, immune signaling, and cell cycle control. Interestingly, treatment with DPI or antioxidants attenuated constitutive Signal Transducer and Activator of Transcription (STAT) activity, as seen by decreased phospho-STAT6 levels and reduced STAT6 DNA binding. This suggests a sensitivity of the Janus kinase (JAK)/STAT pathway in cHL cell lines to O₂⁻ and H₂O₂ depletion. Functional assays confirmed this by demonstrating partial restoration of proliferation or apoptosis in L428 cells that expressed constitutively active STAT6 or were transfected with small interfering RNAs (siRNAs) that targeted STAT regulators. These findings highlight that oxidants, particularly H₂O₂, act as both general oxidative stressors and essential modulators of oncogenic signaling pathways. Specifically, maintenance of oxidant homeostasis is critical for sustaining JAK/STAT-mediated growth and survival programs in cHL cells. Targeting redox homeostasis might offer a promising therapeutic strategy to impair JAK/STAT-driven proliferation and survival in cHL.

Seasonal fluctuations in the chemical composition of fine particulate matter (PM_2.5) are known to influence its toxicological properties; however, their integrated biological effects remain incompletely understood. In this study, PM_2.5 was continuously collected over two consecutive years at a single urban site in Japan and classified by season. The samples were comprehensively characterized for ionic species, metals, carbonaceous fractions, and polycyclic aromatic hydrocarbons (PAHs), and their pulmonary effects were evaluated in vivo following intratracheal administration in mice. Seasonal PM_2.5 exhibited pronounced compositional differences, with higher levels of secondary inorganic aerosol components in summer and enrichment of PAHs and mineral-associated components in winter. These seasonal differences translated into distinct biological responses. Reactive oxygen species (ROS) production (1.6–2.7-fold increase) and bronchoalveolar lavage (BAL) neutrophil infiltration were strongly associated with PAH-rich PM_2.5, whereas interleukin-1α (IL-1α) showed robust positive correlations with mineral components, including K⁺, Ca²⁺, and Mg²⁺, which were predominantly enriched in winter PM_2.5. In contrast, secondary inorganic aerosol species displayed a limited capacity to induce IL-1α. Compared with summer samples, winter PM_2.5 induced significantly higher levels of ROS production and IL-1α (approximately 1.5–2.6-fold increase). Using TLR2- and TLR4-deficient mice, we further demonstrated that PM_2.5-induced increases in BAL cell counts, ROS, IL-6, and TNF-α were partially attenuated in TLR4 knockout mice, indicating a contributory but not exclusive role for TLR4 signaling in PM_2.5-driven pulmonary inflammation. Collectively, these findings demonstrate that seasonal variations in PM_2.5 composition, not particle mass alone, critically shape oxidative stress and innate immune responses in the lungs. In particular, winter PM_2.5 enriched in mineral-associated components preferentially activates IL-1α-mediated alarmin pathways, underscoring the importance of the particle composition in determining seasonal air pollution toxicity.

Plant extracts are rich in various bioactive compounds, such as polyphenols, flavonoids, tannins, terpenoids, phenolic acids, saponins, alkaloids, and polysaccharides. Antioxidant polyphenols are increasingly attracting attention, not only as dietary components but also as valuable food industry byproducts. Resveratrol, present in a wide range of plants, is well recognized for its diverse biological activities, including antioxidant, antitumor, cardioprotective, and neuroprotective effects. Given the importance of intercellular communication in these physiological processes, gap junctions (GJs) composed of connexin (Cx) family proteins are of particular interest because they provide a direct pathway for electrical and metabolic signaling and are key players in maintaining normal organ function and cell development. Aberrations of GJ intercellular communication (GJIC) may result in the progression of cardiovascular and neurological diseases and tumorigenesis. Cx43 and Cx45 play crucial roles in cardiac excitation and contraction, and alterations in their expression are associated with disrupted impulse propagation and the development of arrhythmias. In this study, for the first time, we performed a comparative analysis of the effect of resveratrol on Cx43 and Cx45 GJIC using molecular modeling, a dual whole-cell patch-clamp technique to directly measure GJ conductance (g_j), and other approaches. Our results revealed that resveratrol accomplished the following: (1) inhibited GJ g_j in Cx43- but enhanced it in Cx45-expressing HeLa cells; (2) exerted dose- and time-dependent changes in Cx expression and plaque size; (3) reduced cell viability and proliferation; (4) and altered Cx43 phosphorylation patterns linked to gating and plaque stability. Overall, resveratrol modulates GJIC in a dose-, time-, and connexin type-specific manner.