Phosphorylation of MAP kinase-like proteins mediate the response of the halotolerant alga Dunaliella viridis to hypertonic shock

The microalga Dunaliella viridis has the ability to adapt to a variety of environmental stresses including osmotic and thermal shocks, UV irradiation and nitrogen starvation. Lacking a rigid cell wall, Dunaliella provides an excellent model to study stress signaling in eukaryotic unicellular organisms. When exposed to hyperosmotic stress, UV irradiation or high temperature, a 57-kDa protein is recognized by antibodies specific to mammalian p38, to its yeast homologue Hog1, and to the phospho-p38 MAP kinase motif. This 57-kDa protein appears to be both up-regulated and phosphorylated. Three other proteins (50, 45, 43 kDa) were transiently phosphorylated under stress conditions as detected with an antibody specific to the mammalian phospho c-Jun N-terminal kinase (JNK) motif. Treatment with specific inhibitors of p38 MAP kinase (SB203580) and JNK (SP600125) activities markedly impaired the adaptation of Dunaliella to osmotic stress. From an evolutionary standpoint, these data strongly suggest that MAP kinase signaling pathways, other than ERK, were already operating in the common ancestor of plant and animal kingdoms, probably as early as 1400 million years ago.     

Costimulation via CD55 on human CD4+ T cells mediated by CD97

Decay-accelerating factor (CD55) is a complement regulatory protein, which is expressed by most cells to protect them from complement-mediated attack. CD55 also binds CD97, an EGF-TM7 receptor constitutively expressed on granulocytes and monocytes and rapidly up-regulated on T and B cells upon activation. Early results suggested that CD55 could further enhance T cell proliferation induced by phorbol ester treatment. The present study demonstrates that coengagement of CD55, using either cross-linking mAbs or its natural ligand CD97, and CD3 results in enhanced proliferation of human peripheral blood CD4(+) T cells, expression of the activation markers CD69 and CD25, and secretion of IL-10 and GM-CSF. Recently, an increase in T cell responsiveness in CD55(-/-) mice was shown to be mediated by a lack of complement regulation. In this study, we show that direct stimulation of CD55 on CD4(+) T cells with CD97 can modulate T cell activation but does not interfere with CD55-mediated complement regulation. Our results support a multifaceted role for CD55 in human T cell activation, constituting a further link between innate and adaptive immunity.     

Effects on apoptosis and reactive oxygen species formation by Jurkat cells exposed to 50 Hz electromagnetic fields

The effect of exposure to 50 Hz electromagnetic field on a human T-leukaemia cell line (Jurkat) was investigated by evaluating the reactive oxygen species (ROS) production and apoptosis, both spontaneous and induced by a specific anti Fas/CD95 monoclonal antibody (anti-Fas). Our results suggest that 1 h intermittent (5 min field on/10 min field off) exposure does not affect ROS formation, while a slight but statistically significant decrease of both spontaneous and anti-Fas-induced apoptosis was observed.     

Adiponectin oligomerization state and adiponectin receptors airway expression in chronic obstructive pulmonary disease

Adiponectin (Acrp30) shows several beneficial properties and circulates as different oligomers. The role of Acrp30 in lung is not fully clear, but a link with chronic obstructive pulmonary disease (COPD) has been highlighted. In this study, we analyzed the anthropometrical and biochemical features and evaluated total Acrp30 levels of a COPD cohort without metabolic complications compared to healthy controls. In addition, being the oligomerization state critical for its biological activities, we characterized the pattern of Acrp30 circulating oligomers focusing on the high molecular weight (HMW) oligomers to verify whether it correlates to COPD. Finally, we investigated AdipoR1 and AdipoR2 expression in lung from COPD. Interestingly, we found for the first time that the oligomerization state of Acrp30 is altered in COPD; particularly, we observed that the higher levels of Acrp30 are associated with a significant and specific increase of HMW. In addition, we demonstrated the presence of AdipoRs with a lower expression of AdipoR2 compared to AdipoR1. In conclusion, we demonstrated that in COPD, the higher levels of Acrp30 are associated with the significantly increase of HMW representing the most biologically active forms. The important role of Acrp30 in pathophysiological conditions of lung is supported also by the modulation of AdipoRs with the down regulation of AdipoR2. The low expression of AdipoR2 could suggest a specific role of this receptor, mainly implicated in Acrp30 effects on inflammation and oxidative stress. Thus, total Acrp30, HMW and its receptors could be considered critical targets to improve diagnostic and therapeutic strategies for lung diseases.     

Pendrin in the mouse kidney is primarily regulated by Cl- excretion but also by systemic metabolic acidosis

The Cl(-)/anion exchanger pendrin (SLC26A4) is expressed on the apical side of renal non-type A intercalated cells. The abundance of pendrin is reduced during metabolic acidosis induced by oral NH(4)Cl loading. More recently, it has been shown that pendrin expression is increased during conditions associated with decreased urinary Cl(-) excretion and decreased upon Cl(-) loading. Hence, it is unclear if pendrin regulation during NH(4)Cl-induced acidosis is primarily due the Cl(-) load or acidosis. Therefore, we treated mice to increase urinary acidification, induce metabolic acidosis, or provide an oral Cl(-) load and examined the systemic acid-base status, urinary acidification, urinary Cl(-) excretion, and pendrin abundance in the kidney. NaCl or NH(4)Cl increased urinary Cl(-) excretion, whereas (NH(4))(2)SO(4), Na(2)SO(4), and acetazolamide treatments decreased urinary Cl(-) excretion. NH(4)Cl, (NH(4))(2)SO(4), and acetazolamide caused metabolic acidosis and stimulated urinary net acid excretion. Pendrin expression was reduced under NaCl, NH(4)Cl, and (NH(4))(2)SO(4) loading and increased with the other treatments. (NH(4))(2)SO(4) and acetazolamide treatments reduced the relative number of pendrin-expressing cells in the collecting duct. In a second series, animals were kept for 1 and 2 wk on a low-protein (20%) diet or a high-protein (50%) diet. The high-protein diet slightly increased urinary Cl(-) excretion and strongly stimulated net acid excretion but did not alter pendrin expression. Thus, pendrin expression is primarily correlated with urinary Cl(-) excretion but not blood Cl(-). However, metabolic acidosis caused by acetazolamide or (NH(4))(2)SO(4) loading prevented the increase or even reduced pendrin expression despite low urinary Cl(-) excretion, suggesting an independent regulation by acid-base status.     

Phenol Hydroxylase and Toluene/o-Xylene Monooxygenase from Pseudomonas stutzeri OX1: Interplay between Two Enzymes

Degradation of aromatic hydrocarbons by aerobic bacteria is generally divided into an upper pathway, which produces dihydroxylated aromatic intermediates by the action of monooxygenases, and a lower pathway, which processes these intermediates down to molecules that enter the citric acid cycle. Bacterial multicomponent monooxygenases (BMMs) are a family of enzymes divided into six distinct groups. Most bacterial genomes code for only one BMM, but a few cases (3 out of 31) of genomes coding for more than a single monooxygenase have been found. One such case is the genome of Pseudomonas stutzeri OX1, in which two different monooxygenases have been found, phenol hydroxylase (PH) and toluene/o-xylene monooxygenase (ToMO). We have already demonstrated that ToMO is an oligomeric protein whose subunits transfer electrons from NADH to oxygen, which is eventually incorporated into the aromatic substrate. However, no molecular data are available on the structure and on the mechanism of action of PH. To understand the metabolic significance of the association of two similar enzymatic activities in the same microorganism, we expressed and characterized this novel phenol hydroxylase. Our data indicate that the PH P component of PH transfers electrons from NADH to a subcomplex endowed with hydroxylase activity. Moreover, a regulatory function can be suggested for subunit PH M. Data on the specificity and the kinetic constants of ToMO and PH strongly support the hypothesis that coupling between the two enzymatic systems optimizes the use of nonhydroxylated aromatic molecules by the draining effect of PH on the product(s) of oxidation catalyzed by ToMO, thus avoiding phenol accumulation.     

Flavonoids: old and new aspects of a class of natural therapeutic drugs.

Flavonoids are natural products widely distributed in the vegetable kingdom and currently consumed in large amounts in the daily diet. Flavonoids are capable of modulating the activity of enzymes and affect the behaviour of many cell systems, suggesting that the compounds may possess significant antihepatotoxic, antiallergic, anti-inflammatory, antiosteoporotic and even antitumor activities. This review summarizes available data on these beneficial effects of flavonoids.     

Possible Brucellosis in an Early Hominin Skeleton from Sterkfontein,South Africa

We report on the paleopathological analysis of the partial skeleton of the late Pliocene hominin species Australopithecus africanus Stw 431 from Sterkfontein, South Africa. A previous study noted the presence of lesions on vertebral bodies diagnosed as spondylosis deformans due to trauma. Instead, we suggest that these lesions are pathological changes due to the initial phases of an infectious disease, brucellosis. The macroscopic, microscopic and radiological appearance of the lytic lesions of the lumbar vertebrae is consistent with brucellosis. The hypothesis of brucellosis (most often associated with the consumption of animal proteins) in a 2.4 to 2.8 million year old hominid has a host of important implications for human evolution. The consumption of meat has been regarded an important factor in supporting, directing or altering human evolution. Perhaps the earliest (up to 2.5 million years ago) paleontological evidence for meat eating consists of cut marks on animal remains and stone tools that could have made these marks. Now with the hypothesis of brucellosis in A. africanus, we may have evidence of occasional meat eating directly linked to a fossil hominin.     

Activation of β- and γ-carbonic anhydrases from pathogenic bacteria with tripeptides

Six tripeptides incorporating acidic amino acid residues were prepared for investigation as activators of β- and γ-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic bacteria Vibrio cholerae, Mycobacterium tuberculosis, and Burkholderia pseudomallei. The primary amino acid residues that are involved in the catalytic mechanisms of these CA classes are poorly understood, although glutamic acid residues near the active site appear to be involved. The tripeptides that contain Glu or Asp residues can effectively activate VchCAβ and VchCAγ (enzymes from V. cholerae), Rv3273 CA (mtCA3, a β-CA from M. tuberculosis) and BpsCAγ (γ-CA from B. pseudomallei) at 0.21–18.1?µM levels. The position of the acidic residues in the peptide sequences can significantly affect bioactivity. For three of the enzymes, tripeptides were identified that are more effective activators than both l-Glu and l-Asp. The tripeptides are also relatively selective because they do not activate prototypical α-CAs (human carbonic anhydrases I and II). Because the role of CA activators in the pathogenicity and life cycles of these infectious bacteria are poorly understood, this study provides new molecular probes to explore such processes.