Can hypoosmotic shock and calcium influx lead to translocation of aquaporin-1 in shrimp muscle cells?

The physiological variations during the crustacean molting cycle have intrigued researchers for many years. Maintaining osmotic homeostasis in the face of hemolymph dilution and dealing with dynamic intracellular and extracellular calcium fluctuations are challenges these animals continuously confront. It has recently been shown that water channels present in the cell membrane (aquaporins) are essential for water uptake during premolt and postmolt. This study aims to investigate whether hypoosmotic shock and intracellular and extracellular calcium variations can lead to translocation of Aquaporin 1 (AQP-1) from the intracellular region to the plasma membrane during premolt and postmolt, thus allowing increased water flow in these stages. For this, we investigate in vitro the rapid change of AQP-1 positions in the abdominal muscle cells in the freshwater shrimp, Palaemon argentinus. Using cell volume analysis and immunohistochemistry, we show that hypoosmotic conditions and an elevation of the intracellular and extracellular calcium concentrations are concurrent with the translocation of AQP-1 to the plasma membrane. These results indicate that calcium flux and hypoosmotic shock may be regulators of AQP 1 in the translocation process.

PIP aquaporin pH-sensing is regulated by the length and charge of the C-terminal region.

Plant PIP aquaporins play a central role in controlling plant water status. The current structural model for PIP pH-gating states that the main pH sensor is located in loopD and that all the mobile cytosolic elements participate in a complex interaction network that ensures the closed structure. However, the precise participation of the last part of the C-terminal domain (CT) in PIP pH gating remains unknown. This last part has not been resolved in PIP crystal structures and is a key difference between PIP1 and PIP2 paralogues. Here, by a combined experimental and computational approach, we provide data about the role of CT in pH gating of Beta vulgaris PIP. We demonstrate that the length of CT and the positive charge located among its last residues modulate the pH at which the open/closed transition occurs. We also postulate a molecular-based mechanism for the differential pH sensing in PIP homo- or heterotetramers by performing atomistic molecular dynamics simulations (MDS) on complete models of PIP tetramers. Our findings show that the last part of CT can affect the environment of loopD pH sensors in the closed state. Results presented herein contribute to the understanding of how the characteristics of CT in PIP channels play a crucial role in determining the pH at which water transport through these channels is blocked, highlighting the relevance of the differentially conserved very last residues in PIP1 and PIP2 paralogues.

Mechanochemical Synthesis and Structure of the Tetrahydrate and Mesoporous Anhydrous Metforminium(2+)-N,N'-1,4-Phenylenedioxalamic Acid (1:2) Salt: The Role of Hydrogen Bonding and n→π * Charge Assisted Interactions.

A new organic salt of metformin, an antidiabetic drug, and N,N'-(1,4-phenylene)dioxalamic acid, was mechanochemically synthesized, purified by crystallization from solution and characterized by single X-ray crystallography. The structure revealed a salt-type crystal hydrate composed of one dicationic metformin unit, two monoanionic units of the acid and four water molecules, namely H2Mf(HpOXA)2∙4H2O. X-ray powder, IR, 13C-CPMAS, thermal and BET adsorption-desorption analyses were performed to elucidate the structure of the molecular and supramolecular structure of the anhydrous microcrystalline mesoporous solid H2Mf(HpOXA)2. The results suggest that their structures, conformation and hydrogen bonding schemes are very similar. To the best of our knowledge, the selective formation of the monoanion HpOXA-, as well as its structure in the solid, is herein reported for the first time. Regular O(δ-)∙∙∙C(δ), O(δ-)∙∙∙N+ and bifacial O(δ-)∙∙∙C(δ)∙∙∙O(δ-) of n→π * charge-assisted interactions are herein described in H2MfA organic salts which could be responsible of the interactions of metformin in biologic systems. The results support the participation of n→π * charge-assisted interactions independently, and not just as a short contact imposed by the geometric constraint due to the hydrogen bonding patterns.

Treatment with Mesenchymal Stem Cells Improves Renovascular Hypertension and Preserves the Ability of the Contralateral Kidney to Excrete Sodium.

BACKGROUND: Mesenchymal stem cells (MSC) improve renal function and renovascular hypertension in the 2-kidney 1-clip model (2K-1C). While MSC play an immunomodulatory role, induce neoangiogenesis, and reduce fibrosis, they do not correct sodium loss by the contra-lateral kidney. OBJECTIVES: We investigated the tubular function of both stenotic and contralateral kidneys and the effect of MSC treatment by evaluating diuresis, natriuresis, and the expression of the main water and sodium transporters. METHOD: Adult Wistar rats were allocated into four groups: control (CT), CT+MSC, 2K-1C, and 2K-1C+MSC. MSC (2 × 105) were infused through the tail vein 3 and 5 weeks after clipping. Systolic blood pressure (SBP) was monitored weekly by plethysmography. Six weeks after clipping, 24-hour urine and blood samples were collected for biochemical analysis. Gene expression of the Na/H exchanger-3, epithelial sodium channel, Na/K-ATPase, Na/K/2Cl cotransporter, and aquaporins 1 and 2 (AQP1 and AQP2) were analyzed by RT-PCR. Intrarenal distribution of AQP1 and AQP2 was analyzed by immunohistochemistry. RESULTS: In hypertensive 2K-1C animals, MSC prevented additional increases in BP. AQP1, but not AQP2, was suppressed in the contralateral kidney, resulting in significant increase in urinary flow rate and sodium excretion. Gene expressions of sodium transporters were similar in both kidneys, suggesting that the high perfusing pressure in the contralateral kidney was responsible for increased natriuresis. Contralateral hypertensive kidney showed signs of renal deterioration with lower GFR in spite of normal RPF levels. CONCLUSIONS: MSC treatment improved renal function and enhanced the ability of the contralateral kidney to excrete sodium through a tubular independent mechanism contributing to reduce SBP.

Effect of low radiation dose on the expression and location of aquaporins in rat submandibular gland.

Head and neck cancers are common in several regions of the world and the treatment usually includes radiotherapy. This treatment can generate adverse effects to the salivary flow, with a relationship between the dose and the damage caused. Salivary gland cells are highly permeable to water and therefore, they express aquaporins (AQPs). This study analyzed changes in the expression and location of these proteins and identified morphological changes induced by low radiation in rat submandibular gland. Female rats were divided into control and irradiated groups. Immunohistochemistry analysis allowed confirming the presence of AQP1 in the blood vessel endothelium. Intense and steady labelling granules were also observed in the cytoplasm of submandibular gland ductal cells. In addition, there was AQP5 positive labelling in ductal cells delimiting the lumen of intercalated duct, in the cytoplasm and membrane of acinar cells. Finally, the decrease of AQP labelling in irradiated animal glands validated their radiosensitivity. Thus, the decrease in AQP1 protein levels in the endothelium and AQP5 in gland ductal cells of irradiated animals may have hindered the removal of water from the lumen of ductal cells, inducing a delay in water absorption and triggering a slight lumen increase.

Influencia de las acuaporinas en la génesis de múltiples enfermedades / Aquaporins Influence in the Genesis of Multiple Diseases

Las acuaporinas son una familia de proteínas que forman los canales de agua de la membrana. Están involucradas en una gran variedad de funciones fisiológicas y enfermedades humanas como el glaucoma, cáncer, epilepsia, obesidad entre otras. El descubrimiento de las acuaporinas cambia el panorama con respecto a la comprensión del transporte de agua en las membranas biológicas y a la naturaleza de las proteínas transportadoras en general, porque su estudio demuestra que existen canales en las membranas no sólo permeables a iones y que los movimientos de agua a través de las membranas son regulados por la célula en forma muy diferente a como se pensaba hace una década, esto implica comprender mejor los mecanismos fisiopatológicos que lleven al desarrollo de nuevas medidas terapéuticas y más eficaces para el tratamiento de las enfermedades.

Aquaporins are a family of membrane water channels. They are involved in a great variety of physiological functions and human diseases including, glaucoma, cancer, epilepsy, obesity among others. The discovery of the aquaporins have changed the view regarding the understanding of the transportation of water in the biological membranes and to the nature of the transporting proteins in general, because its study has showed that there are canals not only in permeable membranes to ions and the fact that the movements of water through the membranes are regulated by the cell in very different way, comparing to the considerations that existed a decade ago, this allows the understanding of physiopathologic mechanisms that lead to the development of therapeutic new measures better and more effective for the diseases treatment.

Neuromielitis óptica con alta expresión de acuaporina-4 y anticuerpos anti-acuaporina-4 positivos en suero / Neuromyelitis optica with high aquaporin-4 expression and positive serum aquaporin-4 autoantibodies

La presencia de anticuerpos IgG en suero, con blanco en los canales de acuaporina-4, es específica de la neuromielitis óptica (NMO). El 60% de los pacientes con NMO presentan lesiones cerebrales en la resonancia magnética (RM); en un 8% (mayoría niños) estas lesiones se consideraron "atípicas". Presentamos dos pacientes con NMO y lesiones en el SNC de alta expresión de acuaporina-4. Caso 1: varón de 50 años, que comenzó con pérdida de visión en ojo derecho (OD). Recibió tratamiento empírico con metilprednisolona 1 g/d x 3 días. Al mes presentó dolor generalizado y hemiparesia derecha; nuevamente recibió metilprednisolona 1 g/d x 5 días e IgG IV 400 mg/kg/d × 5 días. Recuperó la deambulación persistiendo el dolor y fenómenos paroxísticos en los 4 miembros. Potenciales evocados visuales: P100, ojo izquierdo (OI) 123 mseg. OD sin respuesta. La RM de cerebro (FLAIR) mostró hiperintensidad en nervio óptico derecho, hipotálamo y comisura blanca anterior. RM cervical: lesión medular extensa (5 cuerpos vertebrales). Caso 2: mujer de 53 años, con disminución de la agudeza visual en ambos ojos y parestesias en miembros inferiores que remitieron espontáneamente. Evolucionó al mes con cuadriparesia e incontinencia esfinteriana. Recibió metilprednisolona 1 g/d x 5 días, sin mejoría. Potenciales evocados visuales: P100 OI 124 mseg. OD 128 mseg. RM cerebro: (FLAIR) hiperintensidad hipotalámica y periacueductal. RM cervical: lesión medular extensa (7 cuerpos vertebrales). Anticuerpos anti-acuaporina-4 positivos en ambos pacientes (inmunofluorescencia indirecta). Las lesiones consideradas "atípicas", como aquí, en sitios con alta densidad de proteínas canales de agua AQP4 deberán considerarse para el diagnóstico diferencial.

Disease-specific aquaporin-4 antibodies (NMO-IgG) are the main effector of lesions in neuromyelitis optica (NMO) patients. Brain MRI lesions are detected in 60% of them, with 8% (almost infants) at sites of high aquaporin-4 expression. Patient 1: A fifty-year-old male with loss of vision in the right eye. Empiric treatment with metilprednisolone 1g/d for 3 days was indicated. After 30 days he complained of generalized pain, and a right hemiparesis was evident. The patient received bolus of metilprednisolone 1g/d for 5 days plus IgG 400 mg/kg/d IV for 5 days. He recovered ambulation but persisted with pain and paroxysmal phenomena (Lhermitte). Visual Evoked Potentials (VEP): P100 left eye 123 ms, right eye without response. Brain MRI (FLAIR) showed hyperintensity in the right optic nerve, hypothalamus and anterior white commissure. Cervical MRI showed extensive spinal cord lesion to an extension of 5 vertebral bodies. Patient 2: A fifty-three-year-old female who referred decreased visual acuity in both eyes and paresthesia in lower limbs which subsided spontaneously. One month later the patient evolved with cuadriparesis and sphincter incontinence. No improvement was observed with bolus of metilprednisolone 1g/d for 5 day. VEP: P100 left eye 124 ms, right eye 128 ms. Brain MRI (FLAIR) disclosed hypothalamic and periaqueductal hyperintensity. Cervical MRI showed extensive spinal cord lesion to an extension of 7 vertebral bodies. NMO-IgG antibodies were positive in both patients (indirect immunofluorescence assay). NMO brain lesions at sites of high aquaporin-4 expression, once considered "atypical" for their topography and infrequency in adults, should be borne in mind when considering differential diagnosis.

Neuromielitis óptica con alta expresión de acuaporina-4 y anticuerpos anti-acuaporina-4 positivos en suero / Neuromyelitis optica with high aquaporin-4 expression and positive serum aquaporin-4 autoantibodies

La presencia de anticuerpos IgG en suero, con blanco en los canales de acuaporina-4, es específica de la neuromielitis óptica (NMO). El 60% de los pacientes con NMO presentan lesiones cerebrales en la resonancia magnética (RM); en un 8% (mayoría niños) estas lesiones se consideraron "atípicas". Presentamos dos pacientes con NMO y lesiones en el SNC de alta expresión de acuaporina-4. Caso 1: varón de 50 años, que comenzó con pérdida de visión en ojo derecho (OD). Recibió tratamiento empírico con metilprednisolona 1 g/d x 3 días. Al mes presentó dolor generalizado y hemiparesia derecha; nuevamente recibió metilprednisolona 1 g/d x 5 días e IgG IV 400 mg/kg/d Î 5 días. Recuperó la deambulación persistiendo el dolor y fenómenos paroxísticos en los 4 miembros. Potenciales evocados visuales: P100, ojo izquierdo (OI) 123 mseg. OD sin respuesta. La RM de cerebro (FLAIR) mostró hiperintensidad en nervio óptico derecho, hipotálamo y comisura blanca anterior. RM cervical: lesión medular extensa (5 cuerpos vertebrales). Caso 2: mujer de 53 años, con disminución de la agudeza visual en ambos ojos y parestesias en miembros inferiores que remitieron espontáneamente. Evolucionó al mes con cuadriparesia e incontinencia esfinteriana. Recibió metilprednisolona 1 g/d x 5 días, sin mejoría. Potenciales evocados visuales: P100 OI 124 mseg. OD 128 mseg. RM cerebro: (FLAIR) hiperintensidad hipotalámica y periacueductal. RM cervical: lesión medular extensa (7 cuerpos vertebrales). Anticuerpos anti-acuaporina-4 positivos en ambos pacientes (inmunofluorescencia indirecta). Las lesiones consideradas "atípicas", como aquí, en sitios con alta densidad de proteínas canales de agua AQP4 deberán considerarse para el diagnóstico diferencial.(AU)

Disease-specific aquaporin-4 antibodies (NMO-IgG) are the main effector of lesions in neuromyelitis optica (NMO) patients. Brain MRI lesions are detected in 60% of them, with 8% (almost infants) at sites of high aquaporin-4 expression. Patient 1: A fifty-year-old male with loss of vision in the right eye. Empiric treatment with metilprednisolone 1g/d for 3 days was indicated. After 30 days he complained of generalized pain, and a right hemiparesis was evident. The patient received bolus of metilprednisolone 1g/d for 5 days plus IgG 400 mg/kg/d IV for 5 days. He recovered ambulation but persisted with pain and paroxysmal phenomena (Lhermitte). Visual Evoked Potentials (VEP): P100 left eye 123 ms, right eye without response. Brain MRI (FLAIR) showed hyperintensity in the right optic nerve, hypothalamus and anterior white commissure. Cervical MRI showed extensive spinal cord lesion to an extension of 5 vertebral bodies. Patient 2: A fifty-three-year-old female who referred decreased visual acuity in both eyes and paresthesia in lower limbs which subsided spontaneously. One month later the patient evolved with cuadriparesis and sphincter incontinence. No improvement was observed with bolus of metilprednisolone 1g/d for 5 day. VEP: P100 left eye 124 ms, right eye 128 ms. Brain MRI (FLAIR) disclosed hypothalamic and periaqueductal hyperintensity. Cervical MRI showed extensive spinal cord lesion to an extension of 7 vertebral bodies. NMO-IgG antibodies were positive in both patients (indirect immunofluorescence assay). NMO brain lesions at sites of high aquaporin-4 expression, once considered "atypical" for their topography and infrequency in adults, should be borne in mind when considering differential diagnosis.(AU)

Neuromielitis óptica con alta expresión de acuaporina-4 y anticuerpos anti-acuaporina-4 positivos en suero / Neuromyelitis optica with high aquaporin-4 expression and positive serum aquaporin-4 autoantibodies

La presencia de anticuerpos IgG en suero, con blanco en los canales de acuaporina-4, es específica de la neuromielitis óptica (NMO). El 60% de los pacientes con NMO presentan lesiones cerebrales en la resonancia magnética (RM); en un 8% (mayoría niños) estas lesiones se consideraron "atípicas". Presentamos dos pacientes con NMO y lesiones en el SNC de alta expresión de acuaporina-4. Caso 1: varón de 50 años, que comenzó con pérdida de visión en ojo derecho (OD). Recibió tratamiento empírico con metilprednisolona 1 g/d x 3 días. Al mes presentó dolor generalizado y hemiparesia derecha; nuevamente recibió metilprednisolona 1 g/d x 5 días e IgG IV 400 mg/kg/d × 5 días. Recuperó la deambulación persistiendo el dolor y fenómenos paroxísticos en los 4 miembros. Potenciales evocados visuales: P100, ojo izquierdo (OI) 123 mseg. OD sin respuesta. La RM de cerebro (FLAIR) mostró hiperintensidad en nervio óptico derecho, hipotálamo y comisura blanca anterior. RM cervical: lesión medular extensa (5 cuerpos vertebrales). Caso 2: mujer de 53 años, con disminución de la agudeza visual en ambos ojos y parestesias en miembros inferiores que remitieron espontáneamente. Evolucionó al mes con cuadriparesia e incontinencia esfinteriana. Recibió metilprednisolona 1 g/d x 5 días, sin mejoría. Potenciales evocados visuales: P100 OI 124 mseg. OD 128 mseg. RM cerebro: (FLAIR) hiperintensidad hipotalámica y periacueductal. RM cervical: lesión medular extensa (7 cuerpos vertebrales). Anticuerpos anti-acuaporina-4 positivos en ambos pacientes (inmunofluorescencia indirecta). Las lesiones consideradas "atípicas", como aquí, en sitios con alta densidad de proteínas canales de agua AQP4 deberán considerarse para el diagnóstico diferencial.(AU)

Disease-specific aquaporin-4 antibodies (NMO-IgG) are the main effector of lesions in neuromyelitis optica (NMO) patients. Brain MRI lesions are detected in 60% of them, with 8% (almost infants) at sites of high aquaporin-4 expression. Patient 1: A fifty-year-old male with loss of vision in the right eye. Empiric treatment with metilprednisolone 1g/d for 3 days was indicated. After 30 days he complained of generalized pain, and a right hemiparesis was evident. The patient received bolus of metilprednisolone 1g/d for 5 days plus IgG 400 mg/kg/d IV for 5 days. He recovered ambulation but persisted with pain and paroxysmal phenomena (Lhermitte). Visual Evoked Potentials (VEP): P100 left eye 123 ms, right eye without response. Brain MRI (FLAIR) showed hyperintensity in the right optic nerve, hypothalamus and anterior white commissure. Cervical MRI showed extensive spinal cord lesion to an extension of 5 vertebral bodies. Patient 2: A fifty-three-year-old female who referred decreased visual acuity in both eyes and paresthesia in lower limbs which subsided spontaneously. One month later the patient evolved with cuadriparesis and sphincter incontinence. No improvement was observed with bolus of metilprednisolone 1g/d for 5 day. VEP: P100 left eye 124 ms, right eye 128 ms. Brain MRI (FLAIR) disclosed hypothalamic and periaqueductal hyperintensity. Cervical MRI showed extensive spinal cord lesion to an extension of 7 vertebral bodies. NMO-IgG antibodies were positive in both patients (indirect immunofluorescence assay). NMO brain lesions at sites of high aquaporin-4 expression, once considered "atypical" for their topography and infrequency in adults, should be borne in mind when considering differential diagnosis.(AU)

I, 2. Physiology and pathophysiology of the gut in relation to viral diarrhea.

Many advances have been made in the understanding of intestinal electrolyte transport from the molecular to the whole-tissue level. This chapter discusses the molecular mechanisms of intestinal epithelial ion transport processes, as well as the intra- and extracellular factors involved in their regulation, as a framework for the understanding of virus-induced gastroenteritis. Based on the present knowledge of the effects of rotavirus (RV) infection on the physiology of the intestine at different levels of organization, a working model for the pathogenesis of RV diarrhea is presented in the chapter. The understanding of the pathogenic processes of viral diarrheas may serve as the basis for a rational approach in the design of novel therapeutic strategies and the search for new antiviral drugs.