Upregulation of aquaporin expression in the salivary glands of heat-acclimated rats

The Impact of High-Temperature Stress on Gut Microbiota and Reproduction in Siberian Hamsters (Phodopus sungorus)

Global warming has induced alterations in the grassland ecosystem, such as elevated temperatures and decreased precipitation, which disturb the equilibrium of these ecosystems and impact various physiological processes of grassland rodents, encompassing growth, development, and reproduction. As global warming intensifies, the repercussions of high-temperature stress on small mammals are garnering increased attention. Recently, research has highlighted that the composition and ratio of gut microbiota are not only shaped by environmental factors and the host itself but also reciprocally influence an array of physiological functions and energy metabolism in animals. In this research, we combined 16S rRNA high-throughput sequencing with conventional physiological assessments, to elucidate the consequences of high-temperature stress on the gut microbiota structure and reproductive capacity of Siberian hamsters (Phodopus sungorus). The results were as follows: 1. The growth and development of male and female hamsters in the high-temperature group were delayed, with lower body weight and reduced food intake. 2. High temperature inhibits the development of reproductive organs in both female and male hamsters. 3. High temperature changes the composition and proportion of gut microbiota, reducing bacteria that promote reproduction, such as Pseudobutyricoccus, Ruminiclostridium-E, Sporofaciens, UMGS1071, and CAG_353. Consequently, our study elucidates the specific impacts of high-temperature stress on the gut microbiota dynamics and reproductive health of Siberian hamsters, thereby furnishing insights for managing rodent populations amidst global climatic shifts. It also offers a valuable framework for understanding seasonal variations in mammalian reproductive strategies, contributing to the broader discourse on conservation and adaptation under changing environmental conditions.

Effect of heat stress on the hypothalamic expression of water channel- and noncoding RNA biogenesis-related genes in modern broilers and their ancestor red jungle fowl

Genetic selection for high growth rate has resulted in spectacular progress in feed efficiency in chickens. As feed intake and water consumption (WC) are associated and both are affected by environmental conditions, we evaluated WC and its hypothalamic regulation in three broiler-based research lines and their ancestor jungle fowl (JF) under heat stress (HS) conditions. Slow growing ACRB, moderate growing 95RB, fast growing MRB, and JF were exposed to daily chronic cyclic HS (36 °C, 9 h/d) or thermoneutral temperature (24 °C). HS increased WC in the MRB only. Arginine vasopressin (AVP) mRNA levels were decreased by HS in the MRB. Within the renin-angiotensin-aldosterone system (RAAS) system, renin expression was increased by HS in the JF, ACRB, and 95RB, while angiotensin I-converting enzyme (ACE), angiotensin II receptors (type 1, AT1, and type 2, AT2) were affected by line. The expression of aquaporin (AQP2, 7, 9, 10, 11, and 12) genes was upregulated by HS, whereas AQP4 and AQP5 expressions were influenced by line. miRNA processing components (Dicer1, Ago2, Drosha) were significantly different among the lines, but were unaffected by HS. In summary, this is the first report showing the effect of HS on hypothalamic water channel- and noncoding RNA biogenesis-related genes in modern chicken populations and their ancestor JF. These results provide a novel framework for future research to identify new molecular mechanisms and signatures involved in water homeostasis and adaptation to HS.

Genetic studies of heat stress regulation in goat during hot climatic condition

Various direct and indirect environmental constraints have an impact on livestock performance. The physiological parameters, such as rectal temperature, heart rate, and respiratory rate, are the primary indicators of thermal stress. Under a stressed environment temperature humidity index (THI) had established as a vital measurement to identify the thermal stress in livestock. THI in association with climatic variations can define the environmental effect as stressful or comfortable for livestock. Goats are small ruminants that adapt to a wide range of ecological variations due to their anatomical and physiological characteristics. However, the productivity of animals declines at the individual level during thermal stress. Stress tolerance can be determined through genetic studies associated with at the cellular level using physiological as well as molecular approaches. Information on genetic association with thermal stress in goats is scanty, this severely affects their survival and hence productivity of livestock. The ever-increasing demand for food across the globe needs deciphering novel molecular markers as well as stress indicators that play a vital role in livestock improvement. This review represents an analysis of current knowledge of phenotypic differences during thermal stress and signifies the importance of physiological responses and their association at the cellular level in goats. The regulation of vital genes associated with thermal stress such as Aquaporins (AQP 0, 1, 2, 4, 5, 6, 8), aquaglyceroporins (AQP3, 7, 9, and 10) and super-aquaporins (AQP 11, 12); BAX inhibitors such as PERK (PKR like ER kinase), IRE 1(inositol-requiring-1); Redox regulating genes such as NOX; Transport of Na+ and K+ such as ATPase (ATP1A1) and several heat shock proteins have been implicated in heat-stress related adaptations have been elucidated. As these changes have a significant impact on production performance as well as on livestock productivity. Such efforts may help in the development of molecular markers and will assist the breeders to develop heat-tolerant goats with improved productivity.

Structural changes and neurotrophic factors upregulation in submandibular gland in a rat model of depression: proposed correlation with stress indicators during and after the relief of depression

This study evaluated the structural changes, the immunohistochemical and gene expression of neurotrophic factors in submandibular gland in a rat model of depression, and their correlation with depression parameters during and after relief of depression by voluntary running. Forty-eight male Wistar rats were divided into control, control-exercise, depression, and depression-exercise groups. Depression was induced using forced swimming protocol, while the relief of depression was induced using the rat voluntary running wheels. The depressive state of rats was evaluated by measuring the immobility duration and the serum corticosterone level. The immune expression was evaluated by measuring the optical densities (ODs) using ImageJ software, and the gene expression levels were investigated. In the depression group, the convoluted ducts appeared dilated with numerous secretory granules. The number of PCNA-stained cells was significantly decreased in the depression group as compared to control group and then significantly increased in the depression-exercise group when compared to the depression group with a negative correlation to stress indicator. The ODs of immuno-expression for the brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) increased significantly in the depression group as compared to control group. Both BDNF and VEGF immuno-expression displayed positive correlation with the stress indicators. Both BDNF and VEGF gene expression results confirmed their immunohistochemical results. The findings of this study explored the role of submandibular gland in secreting neurotrophic factors and raise a flag for the possibility of using salivary secretions as dependable and easy parameter for estimation of chronic stressed patients.Mini AbstractThe submandibular gland neurotrophic factors immuno-expression can be used in estimating chronic depressive disorders as they are correlated with stress indicators during and after the relief of depression.

Aquaporin-5 Dynamic Regulation

Aquaporin-5 (AQP5), belonging to the aquaporins (AQPs) family of transmembrane water channels, facilitates osmotically driven water flux across biological membranes and the movement of hydrogen peroxide and CO₂. Various mechanisms have been shown to dynamically regulate AQP5 expression, trafficking, and function. Besides fulfilling its primary water permeability function, AQP5 has been shown to regulate downstream effectors playing roles in various cellular processes. This review provides a comprehensive overview of the current knowledge of the upstream and downstream effectors of AQP5 to gain an in-depth understanding of the physiological and pathophysiological processes involving AQP5.

Cataglyphis desert ants use distinct behavioral and physiological adaptations to cope with extreme thermal conditions

Some ant species live in hot and arid environments, such as deserts and savannas. Worker polymorphism-variation in worker size and/or morphology within colonies-is adaptive in such ecosystems because it enhances resistance to heat stress and increases the efficiency of resource exploitation. However, species with small, monomorphic workers are also frequently found in these environments. How species with distinct worker size and degrees of polymorphism deal with such stressful environments remains poorly studied. We investigated the behavioral, physiological, and molecular adaptations that may enhance heat and desiccation tolerance in two sympatric species of Cataglyphis desert ants that differ dramatically in worker size and polymorphism: C. viatica is polymorphic, while C. cubica is small and monomorphic. We found that worker size, water content, water loss, and protein regulation play a key role in thermal resistance. (i) Large C. viatica workers better tolerated heat and desiccation stress than did small C. viatica or C. cubica workers. The former had greater water content and lost proportionally less water to evaporation under thermal stress. (ii) Despite their similar size distribution, workers of C. cubica are more heat tolerant than small C. viatica. This higher degree of tolerance likely stemmed from C. cubica workers having greater relative water content. (iii) Under thermal stress, small C. viatica workers metabolized larger quantities of fat and differentially expressed proteins involved in cellular homeostasis. In contrast, C. cubica downregulated the expression of numerous proteins involved in mitochondrial respiration likely reducing ROS accumulation. (iv) Consistent with these results, large C. viatica workers remained active throughout the day; C. cubica workers displayed a bimodal activity pattern, and small C. viatica remained poorly active outside the nest. Our study shows that ecologically similar ant species with different degrees of worker size polymorphism evolved distinct strategies for coping with extreme heat conditions.

Effects of 4-hexylresorcinol administration on the submandibular glands in a growing rat model

Background

4-Hexylresorcinol (4HR) is a food additive and class I histone deacetylase inhibitor. In this study, we examined the effects of 4HR administration on the submandibular gland in a growing rat model.

Methods

Four-week-old rats were used in this study. The experimental group (nine males and eight females) received 12.8 mg/kg of 4HR weekly for 12 weeks. Ten rats (five males and five females) were used as controls. The submandibular glands of rats were collected 12 weeks after the first administration of 4HR. The weight of the glands was measured. Histological analysis, immunoprecipitation-high-performance liquid chromatography (IP-HPLC), and western blotting were performed.

Results

The weights of the rat submandibular glands were higher in the experimental groups than in the control group, especially in male rats (P < 0.05). The vascular endothelial growth factor (VEGF) and testosterone in the submandibular glands were more highly expressed in 4HR-treated male rats than in untreated rats, as detected by both western blotting and immunohistochemistry. The IP-HPLC results demonstrated that the expression levels of Ki67, epidermal growth factor, and testosterone in the submandibular glands were higher in 4HR-treated male rats than in untreated rats.

Conclusions

This study demonstrated that the systemic administration of 4HR increased the weight of submandibular glands in male rats. In addition, the testosterone and VEGF expression levels in the submandibular glands increased owing to 4HR administration.

CD146+Mesenchymal stem cells treatment improves vascularization, muscle contraction and VEGF expression, and reduces apoptosis in rat ischemic hind limb

Peripheral arterial disease (PAD) is an increasingly common narrowing of the peripheral arteries that can lead to lower limb ischemia, muscle weakness and gangrene. Surgical vein or arterial grafts could improve PAD, but may not be suitable in elderly patients, prompting research into less invasive approaches. Mesenchymal stem cells (MSCs) have been proposed as potential therapy, but their effectiveness and underlying mechanisms in limb ischemia are unclear. We tested the hypothesis that treatment with naive MSCs (nMSCs) or MSCs expressing CD146 (^CD146+MSCs) could improve vascularity and muscle function in rat model of hind-limb ischemia. Sixteen month old Sprague-Dawley rats were randomly assigned to 4 groups: sham-operated control, ischemia, ischemia + nMSCs and ischemia+^CD146+MSCs. After 4 weeks of respective treatment, rat groups were assessed for ischemic clinical score, Tarlov score, muscle capillary density, TUNEL apoptosis assay, contractile force, and vascular endothelial growth factor (VEGF) mRNA expression. ^CD146+MSCs showed greater CD146 mRNA expression than nMSCs. Treatment with nMSCs or ^CD146+MSCs improved clinical and Tarlov scores, muscle capillary density, contractile force and VEGF mRNA expression in ischemic limbs as compared to non-treated ischemia group. The improvements in muscle vascularity and function were particularly greater in ischemia+^CD146+MSCs than ischemia + nMSCs group. TUNEL positive apoptotic cells were least abundant in ischemia+^CD146+MSCs compared with ischemia + nMSCs and non-treated ischemia groups. Thus, MSCs particularly those expressing CD146 improve vascularity, muscle function and VEGF expression and reduce apoptosis in rat ischemic limb, and could represent a promising approach to improve angiogenesis and muscle function in PAD.

Ginger facilitates cell migration and heat tolerance in mouse fibroblast cells

The components of ginger root (Zingiber officinale Roscoe) are widely used for various medicinal purposes. Several bioactive compounds have been identified in ginger, including 6‑, 8‑ and 10‑gingerols, and 6‑shogaol, which are agonists of the thermo‑sensors transient receptor potential (TRP) cation channel subfamily V member 1 and TRP ankyrin 1. Our previous study demonstrated that ginger powder may affect human metabolism in vivo. However, the effects of the bioactive compounds of ginger on cells have not been completely elucidated. The present study investigated whether ginger powder extracts could modify cell functions in mouse fibroblast cells. The active components of ginger powder extracts were characterized using high‑performance liquid chromatography. The activation of protein kinases, actin assembly, cell migration, expression levels of heat shock proteins (HSPs) and cell viability after heat shock were analyzed in NIH3T3 mouse fibroblast cells. Subsequently, 6‑, 8‑, 10‑ and 12‑gingerols, as well as 6‑, 8‑ and 10‑shogaols, were detected in ginger powder extracts. The levels of phosphorylated Akt, mTOR, ERK and p38 MAPK increased after a 10‑min stimulation with ginger powder extracts. In addition, HSP expression levels, lamellipodia formation occurring at cell edges, cell migration and tolerance against heat shock were facilitated following ginger powder extract stimulation. These results suggest that ginger modified cell functions, including actin assembly and heat tolerance, in vitro.

Evaluation of Aquaporins 1 and 5 Expression in Rat Parotid Glands After Volumetric Modulated Arc Radiotherapy and Use of Low-Level Laser Therapy at Different Times

Introduction: This experimental study investigated the mRNA expression of aquaporins (AQPs) 1 and 5 in the parotid glands of rats irradiated with volumetric modulated arc therapy (VMAT) and subjected to low-level laser therapy (LLLT) at different time points. Methods: The sample consisted of 30 Wistar rats (Rattus norvegicus) divided into the following groups: control, LLLT alone (LG), radiotherapy alone (RG), and experimental groups that received LLLT at 24 hours (early experimental group [EEG], n=12) and 120 hours (late experimental group [LEG], n=12) after radiotherapy. VMAT was delivered at a single dose (12 Gy) and LLLT was performed with an aluminium-gallium-arsenide diode laser (660 nm, 100 mW), spot area of 0.0028 cm2, energy of 2 J/cm² applied to 3 spots in the region corresponding to the right parotid gland, for 10 consecutive days. The right parotid gland was resected and prepared for RNA extraction. The gene expression of AQPs was evaluated by quantitative polymerase chain reaction (qPCR) using specific TaqMan probes, with the HPRT gene as an internal control. Results: The lowest AQP1 gene expression was 0.83 (0.27) with the use of LLLT 24 hours after radiotherapy (EEG), and the highest was 1.56 (0.80) with the use of LLLT alone (LG). Likewise, the lowest AQP5 gene expression was found in the EEG (mean = 0.88; SD = 0.49) and the highest in the LG (mean = 1.29; SD = 0.33). Conclusion: The use of LLLT after radiotherapy may contribute to the maintenance and an increase of these proteins, even when used at a later time point after radiotherapy.

Salivary Immunoglobulin A Secretion and Polymeric Ig Receptor Expression in the Submandibular Glands Are Enhanced in Heat-Acclimated Rats

Salivary immunoglobulin A (IgA) plays a critical role in mucosal immunity. Chronic exposure to moderate heat induces heat acclimation, which modifies salivary functions. However, the changes in salivary IgA secretion in heat-acclimated rats are unclear. In this study, we investigated salivary IgA secretion and the expression of polymeric Ig receptor (pIgR), a key mediator of mucosal IgA secretion, in the submandibular glands (SMGs) of heat-acclimated rats. Following maintenance at an ambient temperature (T_a) of 24 ± 0.1 °C for 10 days, male Wistar rats were subjected to T_a of 32 ± 0.2 °C for 5 days (HE group) for heat acclimation or maintained at T_a of 24 ± 0.1°C (CN group). The rats were then anesthetized, pilocarpine (0.5 mg/kg) was intraperitoneally injected, and saliva was collected. Afterward, the SMGs and plasma were sampled. The salivary IgA concentration and IgA flow rate were significantly higher in the HE group than in the CN group. Similarly, SMG pIgR expression was significantly higher in HE rats. The levels of plasma cytokines, including interleukin (IL)-5, IL-6, and interferon-γ, were significantly greater in HE rats than in CN rats. Heat acclimation may enhance oral immunity through salivary IgA secretion and pIgR upregulation in the SMGs.

Prophylactic use of probiotic chocolate modulates intestinal physiological functions in constipated rats

BACKGROUND

This study investigated the in vivo prophylactic effect of probiotic chocolate on constipation. Rats were administered chocolate containing 2.5 × 10¹⁰  CFU g^-1 of probiotics daily for 4 weeks and treated with loperamide (5 mg kg^-1 ) daily at the fourth week of treatment.

RESULTS

Probiotic chocolate treatment significantly (P < 0.05) increased the intestinal motility, colon length, fecal moisture content and number of excreted fecal pellets in constipated rats. Moreover, quantitative real-time polymerase chain reaction data and histological images also revealed that both probiotic chocolate LYC and BB12 treatments were capable of upregulating the mRNA expression levels of colonic ZO-1, occludin and AQP8, leading to the maintenance of the defensive barrier function in the constipated rats compared with the negative controls. Interestingly, these treatments also modulated gut bacterial populations by increasing the abundance levels of Lactobacillus and Bifidobacterium, as well as reducing the abundance level of Enterobacteriaceae.

CONCLUSION

The present study demonstrated that probiotic chocolate LYC and BB12 could potentially be used as alternative agents for prophylactic constipation. © 2018 Society of Chemical Industry.

Localization of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) α, β, γ in the three major salivary glands in situ of mice and their response to β-adrenoceptor stimulation

Phosphatidylinositol 4-phosphate 5-kinase (PIP5K), which is composed of three isozymes (α, β and γ), catalyzes the production of phosphatidylinositol bisphosphate (PIP2). This phospholipid functions in membrane trafficking, as an anchor for actin cytoskeletons and as a regulator of intramembranous channels/transporters. It is also a precursor of such second messengers as diacylglycerol, inositol triphosphate and phosphatidylinositol (3,4,5)-triphosphate. In the present study, the expression and localization of endogenous PIP5Ks were examined in the three major salivary glands of young adult mice in situ. In western blotting of normal control glands, immunoreactive bands for individual PIP5Ks were detectable, with the highest density in the parotid gland and the weakest density in the submandibular gland. In immuno-light microscopy under non-stimulated condition, weak immunoreactivity for PIP5Kα was confined to the apical plasmalemma in parotid, but not sublingual or submandibular, acinar cells. Immunoreactivity for PIP5Kβ was weak to moderate and confined to ductal cells but not acinar cells, whereas that for PIP5Kγ was selectively and intensely detected in myoepithelial cells but not acinar cells, and it was weak in ductal cells in the three glands. In western blot of the parotid gland stimulated by isoproterenol, a β-adrenoceptor agonist, no changes were seen in the intensity of immunoreactive bands for any of the PIP5Ks. In contrast, in immuno-light microscopy, the apical immunoreactivity for PIP5Kα in parotid acinar cells was transiently and distinctly increased after the stimulation. The increased immunoreactivity was ultrastructurally localized on most apical microvilli and along contiguous plasma membrane, where membranous invaginations of various shapes and small vesicles were frequently found. It was thus suggested that PIP5Kα is involved in post-exocytotic membrane dynamics via microvillous membranes. The present finding further suggests that each of the three isoforms of PIP5K functions through its product PIP2 discretely in different cells of the glands to regulate saliva secretion.

The Process of Acclimation to Chronic Hypoxia Leads to Submandibular Gland and Periodontal Alterations: An Insight on the Role of Inflammatory Mediators

The exposition to hypoxia is a stressful stimulus, and the organism develops acclimation mechanisms to ensure homeostasis, but if this fails, it leads to the development of pathological processes. Considering the large number of people under hypoxic conditions, it is of utmost importance to study the mechanisms implicated in hypoxic acclimation in oral tissues and the possible alteration of some important inflammatory markers that regulate salivary and periodontal function. It is the aim of the present study to analyze submandibular (SMG) and periodontal status of animals chronically exposed to continuous (CCH) or intermittent (CIH) hypoxia in order to elucidate the underlying molecular mechanisms that may lead to hypoxic acclimation. Adult Wistar rats were exposed to CCH or CIH simulating 4200 meters of altitude during 90 days. Salivary secretion was decreased in animals exposed to hypoxia, being lower in CIH, together with increased prostaglandin E₂ (PGE₂) content, TBARS concentration, and the presence of apoptotic nuclei and irregular secretion granules in SMG. AQP-5 mRNA levels decreased in both hypoxic groups. Only the CCH group showed higher HIF-1α staining, while CIH alone exhibited interradicular bone loss and increased concentration of the bone resorption marker CTX-I. In summary, animals exposed to CIH show a worse salivary secretion rate, which related with higher levels of PGE₂, suggesting a negative role of this inflammatory mediator during hypoxia acclimation. We link the weak immunorreactivity of HIF-1α in CIH with improper hypoxia acclimation, which is necessary to sustaining SMG physiology under this environmental condition. The alveolar bone loss observed in CIH rats could be due mainly to a direct effect of PGE₂, as suggested by its higher content in gingival tissue, but also to the indirect effect of hyposalivation. This study may eventually contribute to finding therapeutics to treat the decreased salivary flow, improving in that way oral health.

Cytosolic phosphoenolpyruvate carboxykinase is a response gene involved in porcine adipocyte adaptation to heat stress

Heat stress (HS) leads to increased lipid storage and expression of cytosolic phosphoenolpyruvate carboxykinase (PCK1) in pig adipocytes. However, the importance of PCK1 activation and lipid storage in the adaptive response to HS is unknown. Therefore, in vitro experiments were conducted to investigate the effect of PCK1 inhibition with 3-mercaptopicolinic acid (3MPA) on lipid storage and adipocyte response during HS. In vitro culture of adipocytes under HS (41.0 °C) increased (P < 0.05) triacylglycerol accumulation compared with control (37.0 °C). HS increased (P < 0.05) reactive oxygen species level and 3MPA further upregulated (P < 0.05) its level. Heat shock protein 70 (HSP70) gene expression was induced (P < 0.05) by HS compared to control, and PCK1 inhibition with 3MPA attenuated (P < 0.05) its induction by HS. The endoplasmic reticulum (ER) stress markers, C/EBP homologous protein (CHOP) was also upregulated by HS and 3MPA further upregulated (P < 0.05) CHOP mRNA level. These results suggest that with inhibition of PCK1 during HS, in vitro cultured adipocytes were less able to induce adaptive responses such as upregulation of HSP70 and triglycerides, and this exacerbated ER stress during HS. Thus, PCK1 may function to alleviate ER stress that occurs during HS.

Genetic diversity and selection signatures of the beef 'Charolais de Cuba' breed

In this study, we used BovineSNP50 Genotyping BeadChip data to estimate the structure, putative ancestral origin as well as to identify regions with selective sweeps that may have had an important role in the adaptation to tropical conditions of the 'Charolais de Cuba' (CHCU) breed. According to a principal component analysis, CHCU samples cluster together with taurine breeds with an estimated 93% of taurus ancestral alleles. Despite the short period since importation, we detected differentiation (Fst = 0.049) between the French Charolaise (CHA) and CHCU. However, CHA breed was the closest breed to CHCU followed by other hybrids breed with a clear CHA origin. Linkage disequilibrium (r²) decay tends to be lower in CHCU compared to CHA probably due to a less intense artificial selection programs of CHCU. Signals of recent adaptation to tropical conditions between CHCU and CHA were identified. Genes mapping within those regions reflect different functions related to immunity, metabolic changes and heat tolerance (CHCU) and muscle development and meat quality (CHA) that may have had an important role in the phenotypic differentiation of these breeds. Further studies will expand our knowledge on the molecular basis of adaptation of cattle to tropical conditions and molecular process associated with meat quality traits.

Daily voluntary exercise enhances pilocarpine-induced saliva secretion and aquaporin 1 expression in rat submandibular glands

Saliva—a water‐based fluid containing electrolytes, immunoglobulins, and enzymes—has many functions, including the protection and hydration of mucosal structures within the oral cavity and the initiation of digestion. Aquaporins (AQPs) are proteins that act as water channels through membranes. We have previously reported upregulation of the expression levels of AQP 1 and 5 in the submandibular glands (SMGs) in heat‐acclimated rats. In this study, we investigated pilocarpine‐induced saliva secretion and AQP expression in rats after voluntary exercise. Male, 10‐week‐old Wistar rats were initially maintained at an ambient temperature of 24 °C for 10 days and were then kept for 40 days in cages either with a running wheel (exercise rats, n = 6) or with a locked wheel [control rats (CN), n = 6]. After the training period, the rats were anesthetized and pilocarpine, an M3 muscarinic receptor agonist, was intraperitoneally injected (0.5 mg·kg⁻¹) to stimulate saliva secretion. Saliva was collected, and the SMGs were sampled and subjected to western blot, RT‐PCR, and immunohistochemical analyses. Pilocarpine induced a greater amount of saliva in the exercised rats than in the CN. Expression levels of AQP1 mRNA and protein were significantly higher in SMGs of exercised rats than in those of the CN, but the expression of AQP5 was not affected by voluntary exercise. Voluntary exercise increased the expression of vascular endothelial growth factor (VEGF) and cluster of differentiation 31 (CD31), a marker for endothelial cells, in the SMGs. Voluntary exercise promoted pilocarpine‐induced saliva secretion, probably via an increase in the expression level of AQP1 due to VEGF‐induced CD31‐positive angiogenesis in the SMG.

SMN regulation in SMA and in response to stress: new paradigms and therapeutic possibilities

Low levels of the survival of motor neuron (SMN) protein cause the neurodegenerative disease spinal muscular atrophy (SMA). SMA is a pediatric disease characterized by spinal motor neuron degeneration. SMA exhibits several levels of severity ranging from early antenatal fatality to only mild muscular weakness, and disease prognosis is related directly to the amount of functional SMN protein that a patient is able to express. Current therapies are being developed to increase the production of functional SMN protein; however, understanding the effect that natural stresses have on the production and function of SMN is of critical importance to ensuring that these therapies will have the greatest possible effect for patients. Research has shown that SMN, both on the mRNA and protein level, is highly affected by cellular stress. In this review we will summarize the research that highlights the roles of SMN in the disease process and the response of SMN to various environmental stresses.

The expression of water channel proteins during human salivary gland development: a topographic study of aquaporins 1, 3 and 5

Some members of aquaporin family (AQP) plays crucial functions in salivary synthesis and secretion. These proteins expression has already been reported during salivary gland formation, however no previous studies in human developing glands have been performed. We evaluated AQP1, 3 and 5 expression through the stages of human salivary gland morphogenesis and discuss the possible role of AQP for glandular maturation. Human salivary glands derived from foetuses aged between 14 and 25 weeks were submitted to immunohistochemistry. At the bud stage, membrane expression of AQP1, 3 and 5 were observed within the epithelial bud cells presenting a similar apicolateral pattern, also found at the pseudoglandular stage, present within the terminal portions of future acini, while AQP5 was also particularly strong at the apical membrane of pre-acinar and pre-ductal cells. AQP5 was co-localised with Cytokeratin 7. Similar AQP1, 3 and 5 expression were observed at the following canalicular stage, where distinct and strongly luminal and acinar AQP5 expression is present. During the final terminal bud stage, AQP1 was only identified in serous acini, myoepithelial and endothelial cells, while differentiated mucous acinar cells and ducts were negative. AQP3 was detected at apicolateral membranes of both mucous and serous acini. AQP5 also showed a diffuse expression in mucous and serous acini, in addition to strong apical membrane expression within lumen of intercalated ductal cells. This topographic analysis of AQP1, 3 and 5 revealed differences in the expression pattern throughout salivary gland developmental stages, suggesting different roles for each protein in human glandular maturation.

Long-term HIF-1α transcriptional activation is essential for heat-acclimation-mediated cross tolerance: mitochondrial target genes

An important adaptive feature of heat acclimation (HA) is the induction of cross tolerance against novel stressors (HACT) Reprogramming of gene expression leading to enhanced innate cytoprotective features by attenuating damage and/or enhancing the response of "help" signals plays a pivotal role. Hypoxia-inducible factor-1α (HIF-1α), constitutively upregulated by HA (1 mo, 34°C), is a crucial transcription factor in this program, although its specific role is as yet unknown. By using a rat HA model, we studied the impact of disrupting HIF-1α transcriptional activation [HIF-1α:HIF-1β dimerization blockade by intraperitoneal acriflavine (4 mg/kg)] on its mitochondrial gene targets [phosphoinositide-dependent kinase-1 (PDK1), LON, and cyclooxygenase 4 (COX4) isoforms] in the HA rat heart. Physiological measures of cardiac HACT were infarct size after ischemia-reperfusion and time to rigor contracture during hypoxia in cardiomyocytes. We show that HACT requires transcriptional activation of HIF-1α throughout the course of HA and that this activation is accompanied by two metabolic switches: 1) profound upregulation of PDK1, which reduces pyruvate entry into the mitochondria, consequently increasing glycolytic lactate production; 2) remodeling of the COX4 isoform ratio, inducing hypoxic-tolerant COX4.2 dominance, and optimizing electron transfer and possibly ATP production during the ischemic and hypoxic insults. LON and COX4.2 transcript upregulation accompanied this shift. Loss of HACT despite elevated expression of the cytoprotective protein heat shock protein-72 concomitantly with disrupted HIF-1α dimerization suggests that HIF-1α is essential for HACT. The role of a PDK1 metabolic switch is well known in hypoxia acclimation but not in the HA model and its ischemic setting. Remodeling of COX4 isoforms by environmental acclimation is a novel finding.

Theobromine up-regulates cerebral brain-derived neurotrophic factor and facilitates motor learning in mice

Theobromine, which is a caffeine derivative, is the primary methylxanthine produced by Theobroma cacao. Theobromine works as a phosphodiesterase (PDE) inhibitor to increase intracellular cyclic adenosine monophosphate (cAMP). cAMP activates the cAMP-response element-binding protein (CREB), which is involved in a large variety of brain processes, including the induction of the brain-derived neurotrophic factor (BDNF). BDNF supports cell survival and neuronal functions, including learning and memory. Thus, cAMP/CREB/BDNF pathways play an important role in learning and memory. Here, we investigated whether orally administered theobromine could act as a PDE inhibitor centrally and affect cAMP/CREB/BDNF pathways and learning behavior in mice. The mice were divided into two groups. The control group (CN) was fed a normal diet, whereas the theobromine group (TB) was fed a diet supplemented with 0.05% theobromine for 30 days. We measured the levels of theobromine, phosphorylated vasodilator-stimulated phosphoprotein (p-VASP), phosphorylated CREB (p-CREB), and BDNF in the brain. p-VASP was used as an index of cAMP increases. Moreover, we analyzed the performance of the mice on a three-lever motor learning task. Theobromine was detectable in the brains of TB mice. The brain levels of p-VASP, p-CREB, and BDNF were higher in the TB mice compared with those in the CN mice. In addition, the TB mice performed better on the three-lever task than the CN mice did. These results strongly suggested that orally administered theobromine acted as a PDE inhibitor in the brain, and it augmented the cAMP/CREB/BDNF pathways and motor learning in mice.

Aquaporin 5 Interacts with Fluoride and Possibly Protects against Caries

Aquaporins (AQP) are water channel proteins and the genes coding for AQP2, AQP5, and AQP6 are clustered in 12q13. Since AQP5 is expressed in serous acinar cells of salivary glands, we investigated its involvement in caries. DNA samples from 1,383 individuals from six groups were studied. Genotypes of eight single nucleotide polymorphisms covering the aquaporin locus were tested for association with caries experience. Interaction with genes involved in enamel formation was tested. The association between enamel microhardness at baseline, after creation of artificial caries lesion, and after exposure to fluoride and the genetic markers in AQP5 was tested. Finally, AQP5 expression in human whole saliva, after exposure to fluoride in a mammary gland cell line, which is known to express AQP5, and in Wistar rats was also verified. Nominal associations were found between caries experience and markers in the AQP5 locus. Since these associations suggested that AQP5 may be inhibited by levels of fluoride in the drinking water that cause fluorosis, we showed that fluoride levels above optimal levels change AQP5 expression in humans, cell lines, and rats. We have shown that AQP5 is involved in the pathogenesis of caries and likely interacts with fluoride.

Long-term heat exposure prevents hypoxia-induced apoptosis in mouse fibroblast cells

Long-term continuous exposure to high ambient temperatures induces complete heat acclimation in humans and animals. However, to date, the effects of long-term exposure to heat stress on cells have not been fully evaluated. In this study, we investigated an adaptive physiological process induced in culture cells by continuous exposure to mild heat stress for 60 days. The results of this investigation provide evidence that after long-term heat acclimation in cells, (1) heat shock protein levels are increased, (2) hypoxia inducible factor-1α (HIF-1α) expression is upregulated, and (3) heat shock-induced and hypoxia-induced apoptoses are attenuated. These results suggest that the hypoxia response pathway is an intrinsic part of the heat acclimation repertoire and that the HIF-1 pathway following long-term heat acclimation induces cells with cross tolerance against hypoxia.

Shiga toxin-2 enhances heat-shock-induced apoptotic cell death in cultured and primary glial cells

The blood-brain barrier (BBB) selectively controls the homeostasis of the central nervous system (CNS) environment using specific structural and biochemical features of the endothelial cells, pericytes, and glial limitans. Glial cells, which represent the cellular components of the mature BBB, are the most numerous cells in the brain and are indispensable for neuronal functioning. We investigated the effects of Shiga toxin on glial cells in vitro. Shiga toxin failed to inhibit cell proliferation but attenuated expression of heat shock protein 70, which is one of the chaperone proteins, in cultured and primary glial cells. Furthermore, the combination of Shiga toxin and a heat shock procedure induced cell apoptosis and decreased cell proliferation in both cells. Thus, we speculate that glial cell death in response to the combination of Shiga toxin and heat shock might weaken the BBB and induce central nervous system complications.

Heat acclimation and cross tolerance to hypoxia: Bridging the gap between cellular and systemic responses

Recent research has suggested a potential for some of the physiological and cellular responses to heat acclimation to carry over to improved tolerance of the novel stresses of another environment. This cross-tolerance is evident in heat-acclimated animals that exhibit enhanced tolerance to either hypoxic or ischemic stress, and is primarily attributed to shared cellular stress response pathways. These pathways include Hypoxia-Inducible Factor-1 (HIF-1) and Heat Shock Proteins (HSP). Whether these shared cellular stress response pathways translate to systemic cross-tolerance (improved exercise tolerance, reduced risk of environment-associated illness) has not been clearly shown, particularly in humans. This review highlights the HIF-1 and HSP pathways and their relationship with systemic acclimation responses, and further examines the potential cellular and systemic adaptations that may result in cross-tolerance between hot and hypoxic environments.

Netrin-1 with stem cells promote angiogenesis in limb ischemic rats

BACKGROUND

Recent findings have elucidated that netrin-1 has ability of promoting angiogenesis besides the functions in nervous system. Autologous mesenchymal stem cells (MSCs) transplantation is now proved to be an effective method to treat peripheral arterial disease. However there are still many patients who cannot complete full treatments. Therefore it is necessary to improve the effectiveness. This study estimated the curative effects in chronic limb ischemia when MSCs allied with netrin-1.

MATERIALS AND METHODS

Thirty-six rats were made into chronic limb ischemia models. They were randomly assigned to four groups, netrin-1 + MSCs group (treated with netrin-1 and MSCs derived from peripheral blood), MSCs group (treated with MSCs individually), netrin-1 group (treated with netrin-1 individually), and control group (treated with saline). Measurements of murine behaviors, vascular endothelial growth factor expression, and capillary density in ischemia limb were performed on days 7, 14, and 28 after treatments; measurements of contraction force in ischemia limb was performed on day 28 after treatments to compare differences among the groups.

RESULTS

Netrin-1 allied with MSCs significantly increased Tarlov score, vascular endothelial growth factor expression, capillary density, and muscular strength in ischemia limb.

CONCLUSIONS

Netrin-1 allied with MSCs derived from peripheral blood significantly promoted angiogenesis in aged rats with chronic limb ischemia. It may be a promising method of treating peripheral arterial disease in the future.