A halocin acting on Na+/H+ exchanger of Haloarchaea as a new type of inhibitor in NHE of mammals

The capability of halocin H6 (a bacteriocin-like protein produced by haloarchaeaHaloferax gibbonsii) to inhibit Na+/H+ exchange (NHE) in mammalian cells and its cardio-protective efficacy on the ischemic and reperfused myocardium were evaluated in the present study. H6 inhibits NHE activity (measured by a flow cytometry method) in a dose-dependent form of cell lines of mammalian origin (HEK293, NIH3T3, Jurkat and HL-1) as well as in primary cell culture from human skeletal muscle (myocytes and fibroblasts).In vivo, an ischemia-reperfusion model in dogs by coronary arterial occlusion was used (two hours of regional ischemia and three hours of reperfusion). In animals treated with halocin H6 there was a significant reduction of premature ventricular ectopic beats and infarct size, whereas blood pressure and heart rate remained unchanged. Up to date, halocin H6 is the only described biological molecule that exerts a, specific inhibitory activity in NHE of eukaryotic cells (AU)

En el presente trabajo se evalúa la capacidad de la halocina H6 (una proteína tipo bacteriocina producida por la haloarchaeaHaloferax gibbonsii) para inhibir el intercambiador Na+/H+ (NHE) de céludas de mamífero y su posible eficacia cardioprotectora frente a los daños causados por isquemia-reperfusión del miocardio. En experimentosin vitro H6 inhibe la actividad de NHE (determinada por citometría de flujo) de forma dosis-dependiente tanto en líneas celulares de mamíferos (HEK293, NIH3T3, Jurkat y HL-1) como en cultivos primarios de miocitos y fibroblastos aislados de músculo esquelético humano. En experimentosin vivo se utilizó un modelo de isquemia-reperfusión en perros por oclusión de la arteria coronaria (dos horas de isquemia y tres de reperfusión). En animales tratados con halocina H6 se produjo una disminución significativa a nivel estadístico, tanto del número de latidos ectópicos ventriculares como del tamaño del infarto, mientras que no se produjeron cambios tanto en la presión sanguínea como en el ritmo cardíaco. Hasta la fecha la halocina H6 es la única molécula biológica descrita que ejerce una actividad inhibidora específica sobre el NHE de células eucariotas (AU)

A halocin acting on Na+/H+ exchanger of haloarchaea as a new type of inhibitor in NHE of mammals.

The capability of halocin H6 (a bacteriocin-like protein produced by haloarchaea Haloferax gibbonsii) to inhibit Na+/H+ exchanger (NHE) in mammalian cells and its cardio-protective efficacy on the ischemic and reperfused myocardium were evaluated in the present study. H6 inhibits NHE activity (measured by a flow cytometry method) in a dose-dependent form of cell lines of mammalian origin (HEK293, NIH3T3, Jurkat and HL-1) as well as in primary cell culture from human skeletal muscle (myocytes and fibroblasts). In vivo, an ischemia-reperfusion model in dogs by coronary arterial occlusion was used (two hours of regional ischemia and three hours of reperfusion). In animals treated with halocin H6 there was a significant reduction of premature ventricular ectopic beats and infarct size, whereas blood pressure and heart rate remained unchanged. Up to date, halocin H6 is the only described biological molecule that exerts a specific inhibitory activity in NHE of eukaryotic cells.

Isolation of the fibrocrystalline body, a structure present in haloarchaeal species, from Halobacterium salinarum.

An organized structure, the fibrocrystalline body (FB), has been isolated from the archaeon Halobacterium salinarum. The structure is also present in, and can be isolated from, other extreme halophilic archaea. FB is present in the cytoplasm during the exponential growth and early stationary phases. This structure is affected by vincristine, an antitumoral drug, which targets tubulin. The drug causes fragmentation of the FB, changes in the cell shape, and growth inhibition. Taken together, these results point toward an important role in the life of the cell for this highly organized structure.

Chemical, biochemical and cellular responses in the digestive gland of the mussel Mytilus galloprovincialis from the Spanish Mediterranean coast.

Mussels (Mytilus galloprovincialis) were sampled in March 1996 from five stations along the Western Mediterranean coast (Barcelona, Ebro Delta, Alboraya, Cullera, Denia) corresponding to urban, industrial and agricultural areas. Different biochemical and cellular markers were determined in the mussels in order to assess the effects and/or exposure to pollutants. The cytochrome P450 system, acetylcholinesterase and metallothioneins were among the biochemical markers selected for the study. Histochemical analysis of ß-glucuronidase and catalase activity were performed as marker enzymes for lysosomes and peroxisomes. Chemical analyses indicated that mussels from Barcelona and Denia as highly exposed to polycyclic aromatic hydrocarbons (PAHs)(1.8-2.7 µg g(-1) w.w. against 0.02-0.10 µg g(-1) w.w.), and polychlorinated biphenyls (PCBs)(132-260 ng g(-1) w.w. against 8-24 ng g(-1) w.w.). This was in agreement with changes in lysosome structure and higher number of peroxisomes in those organisms. High levels of metals (particularly Cr and Cu) were recorded in the digestive gland of Alboraya mussels, which also had elevated metallothionein content (28 nmol g(-1) w.w.) in comparison with the other stations (15-20 nmol g(-1) w.w.). Benzo(a)pyrene hydroxylase (BPH) activity indicated Cullera and Barcelona as possibly polluted sites. The results support the usefulness of the biomarker approach to assess and diagnose environmental pollution. The use of a battery of biomarkers at different levels of biological organization coupled with chemical analysis is highlighted.

Specific inhibition of the halobacterial Na+/H+ antiporter by halocin H6.

Halocins H6 and H4 are bacteriocin-like substances capable of killing sensitive halobacterial cells by affecting the bioenergetic steady state across the membrane. The effect of either halocin on living cells is similar, but the primary target of each is different. Halocin H6 inhibited light-induced Na+ out-flow in membrane vesicles of Halobacterium halobium. H4 did not, but instead slowed the H+ return-flow in the dark after illumination. Halocin H6 adsorbs firmly to both whole cells and membrane vesicles. The conclusion is that the primary target of halocin H6 is the Na+/H+ antiporter. This is important not only insofar as it outlines the mechanism by which a halocin works, but also for the fact that it is the first specific physiological inhibitor of the halobacterial Na+/H+ antiporter to be described.