Stresses, Volume 4, Issue 3 (September 2024) – 11 articles

Understanding the dynamics of physiological changes involved in the acclimation responses of plants after their exposure to repeated cycles of water stress is crucial to selecting resilient genotypes for regions with recurrent drought episodes. Under such background, we tried to respond to questions as: (1) Are there differences in the stomatal-related and non-stomatal responses during water stress cycles in different clones of Coffea canephora Pierre ex A. Froehner? (2) Do these C. canephora clones show a different response in each of the two sequential water stress events? (3) Is one previous drought stress event sufficient to induce a kind of “memory” in C. canephora? Seven-month-old plants of two clones (’3V’ and ‘A1’, previously characterized as deeper and lesser deep root growth, respectively) were maintained well-watered (WW) or fully withholding the irrigation, inducing soil water stress (WS) until the soil matric water potential (Ψ_msoil) reached ≅ −0.5 MPa (−500 kPa) at a soil depth of 500 mm. Two sequential drought events (drought-1 and drought-2) attained this Ψ_msoil after 19 days and were followed by soil rewatering until a complete recovery of leaf net CO₂ assimilation rate (A_net) during the recovery-1 and recovery-2 events. The leaf gas exchange, chlorophyll a fluorescence, and leaf reflectance parameters were measured in six-day frequency, while the leaf anatomy was examined only at the end of the second drought cycle. In both drought events, the WS plants showed reduction in stomatal conductance and leaf transpiration. The reduction in internal CO₂ diffusion was observed in the second drought cycle, expressed by increased thickness of spongy parenchyma in both clones. Those stomatal and anatomical traits impacted decreasing the A_net in both drought events. The ‘3V’ was less influenced by water stress than the ‘A1’ genotype in A_net, effective quantum yield in PSII photochemistry, photochemical quenching, linear electron transport rate, and photochemical reflectance index during the drought-1, but during the drought-2 event such an advantage disappeared. Such physiological genotype differences were supported by the medium xylem vessel area diminished only in ‘3V’ under WS. In both drought cycles, the recovery of all observed stomatal and non-stomatal responses was usually complete after 12 days of rewatering. The absence of photochemical impacts, namely in the maximum quantum yield of primary photochemical reactions, photosynthetic performance index, and density of reaction centers capable of Q_A reduction during the drought-2 event, might result from an acclimation response of the clones to WS. In the second drought cycle, the plants showed some improved responses to stress, suggesting “memory” effects as drought acclimation at a recurrent drought. Full article

Oxidative stress constitutes a main molecular mechanism underlying cardiovascular diseases (CVDs). This pathological mechanism can be triggered by NADPH oxidases (NOXs), which produce reactive oxygen species (ROS). In fact, the different NOXs have been associated with myocardial infarction, atherothrombosis, and stroke. More specifically, we will focus on the implications of NOXs in atherothrombotic stroke. Each NOX member participates in a different way in the several stages of this disease: endothelial dysfunction, immune cell infiltration, foam cell genesis, vascular smooth muscle cells (VSMC) proliferation, and atherosclerotic plaque formation. Additionally, some NOXs are involved in plaque instability, thrombosis, ischemic stroke, and ischemia-reperfusion injury (IRI). Interestingly, the effects of NOXs in this pathology depend on the specific homolog, the cell type in which they are activated, and the stage of the disease. In this review we summarize the most up-to-date information about the implications of vascular NOXs in each of these processes. Finally, we highlight some limitations and future perspectives on the study of NOXs in CVDs. Full article

This study investigates the enhanced production of key therapeutic metabolites (ellagic acid, serotonin, and chlorogenic acid) in response to abiotic stress in in vitro cultures of Quercus suber somatic embryos. Findings indicate significant increases in metabolite levels under various stress conditions, highlighting the potential for commercial-scale production of these compounds, known for their antioxidant, anticancer, and anti-COVID-19 properties. Under osmotic/saline stress, ellagic acid production significantly increased, representing an 80% increase compared to control conditions. In embryos exposed to different stressors, serotonin accumulation showed a six-fold increase under osmotic/saline stress. Although the elicitors used did not increase chlorogenic acid levels, exploring alternative stress types may enhance its production. This research paves the way for sustainable, large-scale production of health-beneficial metabolites, addressing global health challenges and promoting resource sustainability. Full article

Stress is defined as a reaction of the body to any given stressor, external or internal. These stressors are common among participants in sports. Therefore, this study aimed to determine the dynamics of two stress biomarkers during an official cliff diving competition. The sample of participants included six professional cliff divers (three females and three males). Their salivary cortisol (C) and alpha-amylase (AA) samples were collected during a 3-day competition (four samples on day 1 and six samples on days 2 and 3). The analysis of the results showed a non-significant increase in AA from day one to day three. On the other hand, C has an increase in the first two days (0.58 ± 0.16 µg/mL–0.61 ± 0.23 µg/mL) and then a decrease in the last competition day (0.53 ± 0.23 µg/mL). Analysis of samples collected during each day demonstrates a fluctuation of the biomarkers. For AA, the sample after the training dive on the 2nd day has the highest value (326.34 ± 280.73 U/mL), whereas on day 3, the samples after training and before the competition dive are the highest (364.50 ± 287.13 U/mL; 466.49 ± 218.39 U/mL). Regarding C levels, the sample after the competition dive tends to show the highest values (0.66 ± 0.17 µg/mL; 0.89 ± 0.29 µg/mL; 0.76 ± 0.32 µg/mL, respectively). Furthermore, the correlation between the results of competition and biomarkers is not significant. These results demonstrate how cliff diving competition tends to have a high impact on the sympathetic nervous system, as observed mainly in AA dynamics. One might contend that even though there is no significant physical strain, cliff divers demonstrate heightened stress biomarker levels that could affect their performance and focus while diving. Full article

Millet, a vital and nutritionally dense cereal extensively cultivated in Sub-Saharan Africa, plays a key role in ensuring food security. This study investigates the starch synthase (SS) gene family, which is crucial for starch biosynthesis and influences various plant functions and stress responses. While the specific roles of SS genes in millet under drought conditions are not fully elucidated, this research provides a thorough analysis of the SS gene family in millet. A total of twelve millet SS genes (SiSSs) were identified and classified into four subfamilies (I–IV) through gene structure and phylogenetic analysis. The SiSS genes were unevenly distributed across millet chromosomes, with cis-acting elements associated with plant growth and stress defense being identified. Quantitative PCR (qPCR) revealed dynamic and varied expression patterns of SiSSs in different tissues under drought stress. Millet plants subjected to drought conditions showed higher tissue starch content and increased starch synthase activity compared to controls. Importantly, the expression levels of the twelve SiSSs were positively correlated with both starch content and synthase activity, suggesting their significant role in drought tolerance. This study enhances our understanding of the millet SS gene family and highlights the potential of these genes in breeding programs aimed at developing drought-resistant millet varieties. Further research is recommended to validate these findings and delve deeper into the mechanisms underlying drought tolerance. Full article

Diabetes mellitus (DM) induces the production of reactive oxygen species, which may lead to cell injury and death. This study aimed to assess the effects of rosmarinic acid (RA) on testicular damage, oxidative stress, and apoptosis in streptozotocin (STZ)-induced diabetic albino mice. DM in four- to six-week-old BALB/c male albino mice was induced via 50 mg/kg STZ, IP for 5 days. Twelve mice were randomly assigned into each of following groups: a control group, a diabetic (DM) group, RA5 mg/kg and RA15 mg/kg groups, and DM + RA5 mg/kg and DM + RA15 mg/kg groups. RA doses were intraperitoneally injected six times a week for seven weeks. Diabetes increased blood sugar and HbA1c levels and decreased all assessed sperm parameters. Testicular tissues of the diabetic mice showed increased lipid peroxidation, decreased reduced glutathione levels and catalase and superoxide dismutase activities, and increased apoptosis associated with histological abnormalities. Both RA doses had no effects on final body weight, blood sugar, and HbA1c in the diabetic mice. It is concluded that the administration of the potent antioxidant RA to diabetic mice improved the redox status in testicular tissues, protected them from diabetes-induced oxidative damage, and improved the quality of spermatozoa, mostly in a dose-dependent manner, which suggests a potential application value of RA in treating DM-related testicular injury and perhaps other complications. Full article

The endoplasmic reticulum (ER) is a vital cell organelle that is primarily involved in the processes of protein folding, maintenance of intracellular calcium storage and lipid synthesis in order to maintain cellular homeostasis. To achieve this meticulous order, several ER-dependent processes have to be in unison and perfect harmony. However, a persistent supply of newly synthesized proteins strains the ER mainly due to the accumulation of unfolded proteins, thus ultimately leading to an imbalance termed ER stress. Although the accumulation of misfolded proteins is a frequent reason for the initiation of ER stress, it is also induced by the hyper-production of reactive oxygen species, aberrant calcium leakage from the ER and due to the effect of cytokines. ER stress signals are conveyed via three arms of ER, namely PERK, IRE1 and ATF6. Signal transduction form these signaling molecules often converges on the transcriptional upregulation of CHOP and its related signaling mechanisms. If the ER stress is unresolved, then it can lead to cell death through different cell death mechanisms, including apoptosis, proptosis, etc. In the liver, it has been observed that ER stress plays a critical role in hepatic damage under different experimental conditions. This review highlights the role of ER stress in liver pathologies. Full article

Rice is one of the most important staple foods globally, sustaining over half of the world’s population. However, the sustainability of grain production is increasingly threatened by heat stress, which is intensified by global climate change. Heat stress, characterized by temperatures exceeding crop-specific optimal growth thresholds, significantly impacts the rice yield and quality, particularly during critical reproductive stages. This review synthesizes current research on strategies to mitigate heat stress in rice through genetic and agronomic approaches. It highlights the implementation of advanced genetic tools such as marker-assisted selection (MAS) and genomic selection (GS) to accelerate the breeding of heat-tolerant rice varieties. Additionally, it discusses sustainable agronomic practices, including adjusting planting dates, optimizing water management, and crop rotation, which enhance resilience to heat stress. The objective of this review is to bridge the gap between research findings and practical agricultural applications, providing a comprehensive resource that guides future research directions and informs policy interventions. This review emphasizes the importance of integrating genetic innovations with traditional and modern farming practices to develop rice varieties that can withstand the adverse effects of heat stress, ensuring food security and agricultural sustainability in the face of climatic challenges. Full article

Chronic exposure to the nephrotoxic metal pollutant, cadmium (Cd), has been associated with hypertension, but the mechanism by which it raises blood pressure is not understood. We hypothesize that exposure to Cd reduces the glomerular filtration rate (GFR), which in turn causes a rise in blood pressure. Data were collected from 447 Thai subjects with a mean age of 51.1 years, of which 48.8% had hypertension, 15.4% had diabetes, and 6.9% had an estimated GFR (eGFR) below 60 mL/min/1.73 m² (low eGFR). More than half (58.8%) and 23.9% had moderate and severe tubular proteinuria, respectively. The mean blood and urinary Cd concentrations were 2.75 and 4.23 µg/L, respectively. Doubling of body burden of Cd increased the prevalence odds ratios (POR) for low eGFR and severe tubular proteinuria 41% and 48%, respectively. The POR for hypertension rose twofold in those with blood Cd levels of 0.61–1.69 µg/L or urinary Cd excretion levels ≥ 0.98 µg/g creatinine. In the hypertensive group, the eGFR was inversely associated with age (β = −0.517), the Cd excretion rate (β = −0.177), and diabetes (β = −0.175). By mediation analysis, an increase in SBP was attributable totally to the effect of Cd on GFR. Thus, blood pressure appeared to rise as GFR fell. This finding is consistent with the well-known role of the kidney in long-term blood pressure regulation, and explains a universally high prevalence of hypertension among patients with low eGFR. Full article

In very high gravity (VHG) fermentation, yeast cells are subjected to a multitude of challenging conditions, including the osmotic pressure exerted by the high sugar content of the wort and the stress factors associated with the high ethanol concentrations present at the end of the fermentation cycle. The response of this biological system to abiotic stresses may be enhanced through biochemical and physiological routes. Silica may play a significant role in regulating the cellular homeostasis of yeast. Alternatively, it is expected that this outcome may be achieved through biochemical responses from the effects of vitamins on yeast cells and the physiological yeast route changing by the culture medium aeration. The objective of this study was to investigate the effects of adding 500 mg L⁻¹ of silica on corn ethanol wort medium and the possibility of supplementing the same wort with vitamins alongside aeration (0.2 v v⁻¹ min⁻¹) as an alternative resource to sustain the fermentation yield rather than adding silica in a fed-batch fermentation cycle with yeast recycling. Upon completion of the five fermentation cycles, yeast samples subjected to the treatment with the addition of silica exhibited a 3.1% higher fermentation yield in comparison to the results observed in the vitamins plus aeration medium bath. Even though greater biomass production (19.1 g L⁻¹) was observed through aerobic yeast behavior in vitaminized supplemented corn medium, the provided silica had a more beneficial effect on yeast stress relief for very high gravity fermentation in a corn hydrolyzed wort with cell recycling. Full article

Stress granules (SGs) are cytoplasmic membraneless compartments that can form in stressed cells. There is an intricate relationship between SGs and innate immune signaling pathways. A previous study reported that the innate immune signaling mediated by Toll-like receptors (TLRs) can inhibit SGs induced by endoplasmic reticulum stress (ER stress) in bone-marrow-derived macrophages (BMDMs) and the chemotherapy drug oxaliplatin in B16 melanoma cells. We wanted to test if this observation can be generalized to other cell types. First, we recapitulated the results from the previous study showing TLR signaling-mediated inhibition of SGs in BMDMs induced by ER stress. However, SGs formed in response to ER stress were either not inhibited or only very weakly inhibited by TLR4 stimulation in human lung cancer-derived A549 cells, murine immortalized mouse lung fibroblasts (iMLFs) and primary murine mouse lung fibroblasts. This correlated with a weak induction of IKK complex kinase activity by TLR4 stimulation in these cells. SGs formed by sodium arsenite treatment also remained unaffected by TLR4 signaling. Our results indicate that the innate immune signaling-mediated inhibition of SGs is cell-type-dependent, thus opening a new avenue for mechanistic studies of the crosstalk between innate immune and stress signaling pathways. Full article