Possible causes of the physiological decline in soybean nitrogen fixation in the presence of nitrate

Nodulated soybean plants (Glycine max (L.) Merr. cv. Clarke)were supplied with 10 mol m^-3 nitrate at the vegetative stage.This treatment caused a rapid decline in nitrogen fixation (acetylenereduction) activity and a consequent decline in ureides in thexylem sap. However, there was virtually no effect on the nitrogenasecomplex, according to Western blots against components 1 and2. The effect on nitrogen fixation was matched by a decreasein nitrogenase-linked respiration and increases in nodule oxygendiffusion resistance and the carbon cost of nitrogen fixation.The addition of nitrate had little effect on protein contentfrom either nodule plant or bacteroid fractions. Activitiesof nitrate reductase (NR) and nitrite reductase (NiR) from eitherthe plant fraction or the bacteroids were affected in differentways during 8 d of supply. Nodule plant NR and bacteroid NiR were not affected. However,nodule plant NiR increased 5-fold within 2 d of supplying Bacteroid NR only increased after6 d. These results could be interpreted in terms of a restrictednitrate access into the infected region of nodules. However,denitrification was detected within 2 d of nitrate supply insoybean nodules. The results are discussed in relation to possiblecauses of the nitrate-induced decline in nitrogenase activity. Key words: Glycine max, nitrate, nitrogen fixation, nodules     

New insights of P2X7 receptor signaling pathway in alveolar functions

Purinergic P2X7 receptor (P2X7R), an ATP-gated cation channel, is unique among all other family members because of its ability to respond to various stimuli and to modulate pro-inflammatory signaling. The activation of P2X7R in immune cells is absolutely required for mature interleukin -1beta (IL-1beta) and IL-18 production and release. Lung alveoli are lined by the structural alveolar epithelial type I (AEC I) and alveolar epithelial type II cells (AEC II). AEC I plays important roles in alveolar barrier protection and fluid homeostasis whereas AEC II synthesizes and secrete surfactant and prevents alveoli from collapse. Earlier studies indicated that purinergic P2X7 receptors were specifically expressed in AEC I. However, their implication in alveolar functions has not been explored. This paper reviews two important signaling pathways of P2X7 receptors in surfactant homeostatsis and Acute Lung Injury (ALI). Thus, P2X7R resides at the critical nexus of alveolar pathophysiology.     

PDZK1 Is a Novel Factor in Breast Cancer That Is Indirectly Regulated by Estrogen through IGF-1R and Promotes Estrogen-Mediated Growth

Although a relationship between PDZK1 expression and estrogen receptor (ER)-α stimulation has been suggested, the nature of such a connection and the function of PDZK1 in breast cancer remain unknown. Human tissue microarrays (cancer tissue: 262 cores; normal tissue: 87 cores) and breast cancer cell lines were used to conduct the study. We show that PDZK1 protein expression is tightly correlated with human breast malignancy, is negatively correlated with age and had no significant correlation with ER-α expression levels. PDZK1 exhibited an exclusive epithelial expression with mostly cytosolic subcellular localization. Additionally, 17β-estradiol induced PDZK1 expression above its basal level more than 24 h after treatment in MCF-7 cells. PDZK1 expression was indirectly regulated by ER-α stimulation, requiring insulinlike growth factor 1 receptor (IGF-1R) expression and function. The molecular link between PDZK1 and IGF-1R was supported by a significant correlation between protein and mRNA levels (r = 0.591, p < 0.001, and r = 0.537, p < 0.001, respectively) of the two factors in two different cohorts of human breast cancer tissues. Interestingly, PDZK1 knockdown in MCF-7 cells blocked ER-dependent growth and reduced c-Myc expression, whereas ectopic expression of PDZK1 enhanced cell proliferation in the presence or absence of 17β-estradiol potentially through an increase in c-Myc expression, suggesting that PDZK1 has oncogenic activity. PDKZ1 also appeared to interact with the Src/ER-α/epidermal growth factor receptor (EGFR) complex, but not with IGF-1R and enhanced EGFR-stimulated MEK/ERK1/2 signaling. Collectively, our results clarify the relationship between ER-α and PDZK1, propose a direct relationship between PDZK1 and IGF-1R, and identify a novel oncogenic activity for PDZK1 in breast cancer.     

Aging bone marrow mesenchymal stromal cells have altered membrane glycerophospholipid composition and functionality

Human mesenchymal stem/stromal cells (hMSC) are increasingly used in advanced cellular therapies. The clinical use of hMSCs demands sequential cell expansions. As it is well established that membrane glycerophospholipids (GPL) provide precursors for signaling lipids that modulate cellular functions, we studied the effect of the donor''s age and cell doublings on the GPL profile of human bone marrow MSC (hBMSC). The hBMSCs, which were harvested from five young and five old adults, showed clear compositional changes during expansion seen at the level of lipid classes, lipid species, and acyl chains. The ratio of phosphatidylinositol to phosphatidylserine increased toward the late-passage samples. Furthermore, 20:4n-6-containing species of phosphatidylcholine and phosphatidylethanolamine accumulated while the species containing monounsaturated fatty acids (FA) decreased during passaging. Additionally, in the total FA pool of the cells, 20:4n-6 increased, which happened at the expense of n-3 polyunsaturated FAs, especially 22:6n-3. The GPL and FA correlated with the decreased immunosuppressive capacity of hBMSCs during expansion. Our observations were further supported by alterations in the gene expression levels of several enzymes involved in lipid metabolism and immunomodulation. The results show that extensive expansion of hBMSCs harmfully modulates membrane GPLs, affecting lipid signaling and eventually impairing functionality.     

Aldose Reductase Inhibition Prevents Allergic Airway Remodeling through PI3K/AKT/GSK3β Pathway in Mice

Background

Long-term and unresolved airway inflammation and airway remodeling, characteristic features of chronic asthma, if not treated could lead to permanent structural changes in the airways. Aldose reductase (AR), an aldo-sugar and lipid aldehyde metabolizing enzyme, mediates allergen-induced airway inflammation in mice, but its role in the airway remodeling is not known. In the present study, we have examined the role of AR on airway remodeling using ovalbumin (OVA)-induced chronic asthma mouse model and cultured human primary airway epithelial cells (SAECs) and mouse lung fibroblasts (mLFs).

Methods

Airway remodeling in chronic asthma model was established in mice sensitized and challenged twice a week with OVA for 6 weeks. AR inhibitor, fidarestat, was administered orally in drinking water after first challenge. Inflammatory cells infiltration in the lungs and goblet cell metaplasia, airway thickening, collagen deposition and airway hyper-responsiveness (AHR) in response to increasing doses of methacholine were assessed. The TGFβ1-induced epithelial-mesenchymal transition (EMT) in SAECs and changes in mLFs were examined to investigate AR-mediated molecular mechanism(s) of airway remodeling.

Results

In the OVA-exposed mice for 6 wks inflammatory cells infiltration, levels of inflammatory cytokines and chemokines, goblet cell metaplasia, collagen deposition and AHR were significantly decreased by treatment with AR inhibitor, fidarestat. Further, inhibition of AR prevented TGFβ1-induced altered expression of E-cadherin, Vimentin, Occludin, and MMP-2 in SAECs, and alpha-smooth muscle actin and fibronectin in mLFs. Further, in SAECs, AR inhibition prevented TGFβ1- induced activation of PI3K/AKT/GSK3β pathway but not the phosphorylation of Smad2/3.

Conclusion

Our results demonstrate that allergen-induced airway remodeling is mediated by AR and its inhibition blocks the progression of remodeling via inhibiting TGFβ1-induced Smad-independent and PI3K/AKT/GSK3β-dependent pathway.     

Modulation of NSAID-induced antinociceptive and anti-inflammatory effects by alpha2-adrenoceptor agonists with gastroprotective effects

Tizanidine, an alpha2-adrenergic receptor agonist with myospasmolytic action, is indicated for the treatment of back pain either as monotherapy or in combination with nonsteridal anti-inflammatory drugs (NSAIDs). Tizanidine (0.25-1.0 mg/kg) significantly produced analgesic and anti-inflammatory effect in acetic acid induced writhing in mice and carrageenan-induced paw edema in rats, respectively. The effects were comparable with clonidine (0.25 and 0.50 mg/kg), another alpha2-agonist. Yohimbine (1 mg/kg), alpha2-adrenergic antagonist reversed the effect of tizanidine. Tizanidine (0.25 mg/kg) and clonidine (0.25 mg/kg) significantly potentiated the antinociceptive and anti-inflammatory effect of NSAIDs (nimesulide, meloxicam and naproxen). Tizanidine (1 mg/kg) did not alter basal pH, acidity (free and total) of gastric content and did not produce any mucosal injury in fasted rats. Tizanidine (1 mg/kg) significantly reduced meloxicam (UD50 3.21 mg/kg), nimesulide (UD50 24.52 mg/kg) and naproxen (UD50 14.10 mg/kg)-induced ulcerogenic effect (ulcer index, pH and free/total acidity). It is expected that tizanidine exerted gastrotprotection through stimulation of gastric and central alpha2-adrenergic receptors. Present investigation suggested that tizanidine not only enhance the analgesic and anti-inflammatory effect of NSAIDs but also improved gatstrointestinal tolerability of NSAIDs through modulation of central alpha-2-receptors. From this study, it can be speculated that tizanidine and NSAID combination therapy would prove to be a novel approach to treat nociceptive/inflammatory conditions with improved gastric tolerability of NSAIDs.     

Host plant nodule parameters associated with nitrogen fixation efficiency in French bean (Phaseolus vulgaris L) cultivars

Two cultivars of French bean (Phaseolus vulgaris L.) viz. contender and arka komal were planted in polythene bags containing sand and grown under glasshouse conditions. The nodulation status, shoot/root biomass, activities of several nodule enzymes, total soluble protein and leghaemoglobin contents were monitored over the entire growth period. Allantoinase activity in leaves was measured to monitor the ureide degrading capacity. Significant genotype difference was observed in both the cultivars. All the parameters showed a decline after flowering except uricase, which declined before flowering. Malate dehydrogenase and isocitrate dehydrogenase showed a constant decline throughout the growth period. Degree of decline varied with the genotype for all the parameters. Leghaemoglobin content, PEP carboxylase activity and ureide degrading capacity of leaves did not show an appreciable decline in contender and were significantly higher than in arka komal. These factors can be used to increase nitrogen fixation in French bean.