Expression and Localization of Aquaporin 4 and Aquaporin 5 along the Large Intestine of Colostrum-Suckling Buffalo Calves

Colostrum Composition, Characteristics and Management for Buffalo Calves: A Review

In this review, the composition, characteristics, and management of dairy buffalo calves were examined and compared with bovines. The neonatal period is critical for buffalo calves and is characterized by a high mortality rate (more than 40%). The early intake of high-quality colostrum (IgG > 50 mg/mL) is the one way to improve the immune system of calves (serum IgG > 10 mg/mL after 12 h), thus increasing their chances of survival. Mainly in intensive farms, the availability of high-quality colostrum is necessary; thus, good quality colostrum is often stored to provide newborn calves which cannot be fed by their mothers. Also, the manipulation of the immunological status of animals through vaccination has been depicted since the quality of colostrum tended to be influenced by vaccination against pathogens. Buffalo breeding is constantly expanding in Italy, mainly thanks to the Mozzarella cheese production that represents the excellence of the "Made in Italy" and is exported worldwide. Indeed, high calf mortality rates directly affect the profitability of the business. For these reasons, the aim of this review was to examine specific research on buffalo colostrum that, compared with other species, are scarce. Improving the knowledge of buffalo colostrum, in terms of characteristics and management, is critical to guarantee buffalo newborns' health in order to reduce their mortality rate. Importantly, considering the knowledge on cattle valid also for buffalo is a widespread, and often erroneous, habit in several fields, including colostrum feeding. Therefore, the two species were compared in this review.

Aquaporins in the nervous structures supplying the digestive organs – a review

Aquaporins (AQPs) are a family of integral membrane proteins which form pores in cell membranes and take part in the transport of water, contributing to the maintenance of water and electrolyte balance and are widely distributed in various tissues and organs. The high expression of AQPs has been described in the digestive system, where large-scale absorption and secretion of fluids occurs. AQPs are also present in the nervous system, but the majority of studies have involved the central nervous system. This paper is a review of the literature concerning relatively little-known issues, i.e. the distribution and functions of AQPs in nervous structures supplying the digestive organs.

Aquaporin 1 (AQP1) Expression in Healthy Dog Tears

Simple Summary

The characterisation of tear proteins is very important for scientists and clinicians, as it enhances their understanding of ocular physiological phenomena that sometimes evolve into diseases. Recently, ophthalmic research has been focused on aquaporins (AQPs), a family of water channel proteins that are largely ubiquitous in body tissues and are known for their role in water and small solute transport across cell membranes. Based on AQPs’ presumable role in the eye, the aim of the present study was to investigate the expression of aquaporin-1 (AQP1) by Western blot analysis in canine eye tears. To this end, we collected tears from both eyes of 15 healthy dogs by employing two tear collection methods: Schirmer tear strips (STS) and ophthalmic sponges (OS). Moreover, ocular parameters such as Schirmer tear test 1 (STT 1), intraocular pressure (IOP), and tear film break up time (BUT) were measured, and fluorescein and lissamine green staining were performed to uncover possible correlations among the aforementioned parameters. Our results showed that the expression of AQP1 in tears collected by both methods and expressed as multiple bands (measured by densitometry) was higher for the tears collected by OS than for those collected by STS. This work forms the basis of future studies aiming to understand and establish the involvement of AQPs in the production and secretion of tears.

Abstract

Aquaporins (AQPs) are a family of thirteen membrane proteins that play an essential role in the transport of fluids across the cell plasma membrane. Recently, the expression of AQPs in different ocular tissues and their involvement in the pathophysiology of eye diseases, have garnered attention. Considering that literature on AQP expression in the lacrimal glands and their secretion is scarce, we aimed to characterise AQP1 expression in the tears of healthy dogs using two tear collection methods (Schirmer tear strips (STS) and ophthalmic sponges (OS)). Fifteen healthy dogs, free of ophthalmic diseases, were included in the study. Tear collection was performed by using STS in one eye and OS in the other. After the extraction of proteins from the tears, the expression of AQP1 was analysed by Western blotting. AQP1 was expressed as a band of 28 kDa. In addition, differences were observed in the expression of AQP1 and in the correlation between tear volume and protein concentration, in tears collected by the two different methods. Our results suggest that AQP1 has a specific role in tear secretion; further research is required to assess its particular role in the function of the ocular surface in eye physiology and pathology.

Urocortinergic system in the epididymis of the normal and cryptorchid dogs

Cryptorchidism is associated with changes in the gonads and the spermatic duct system, which may cause infertility problems. Urocortin (UCN) is a corticotrophin-releasing hormone (CRH)-related peptide, which affects several functions of male genital organs. The aim of the present study was to investigate the expression of UCN and its receptors CRHR1 and CRHR2 using immunohistochemistry, western blotting and real-time reverse transcription polymerase chain reaction in tissues collected from the epididymis of normal and cryptorchid dogs. The lumen of the cryptic epididymal duct was found to be relatively smaller than that of the normal one, and interstitial tissue was abundant in the cryptic epididymis. In addition, only a few spermatids were observed in the lumen of the epididymal duct. Results showed that UCN, CRHR2 and CRHR1 were expressed in tissues collected from normal and cryptic epididymal ducts. Urocortin- and CRHR2-immunoreactivities (IRs) were detected in the principal cells of the caput, corpus and cauda of the normal and cryptic epididymides. CRHR1-IR was detected in vascular smooth muscles and fibromuscular cells surrounding epididymal tubules of the normal and cryptorchid dogs. Expression levels of UCN and CRHR2 mRNA were higher in cryptic epididymal ducts than that in normal epididymal ducts. These results suggest that UCN and its receptors might play a role in regulating the maturation and storage of spermatozoa. These findings indicated that the expression of these proteins could be modulated by the cryptorchidism condition.

Distinct expression and clinical value of aquaporin 4 in children with hand, foot and mouth disease caused by enterovirus 71

Brain dysfunction is a prerequisite for critical complications in children with hand, foot, and mouth disease (HFMD). Aquaporin 4 (AQP-4) may be involved in the pathological process of cerebral oedema and injury in children with severe and critical HFMD. This study aimed to assess the association of AQP-4 with the severity of enterovirus 71 (EV71)-associated HFMD. Children with EV71-infected HFMD were divided into a common group (clinical stage 1), a severe group (clinical stage 2), and a critical group (clinical stage 3) according to Chinese guidelines. The levels of AQP-4, interleukin-6 (IL-6), norepinephrine (NE), and neuron-specific enolase (NSE) before and after treatment were tested. Serum AQP-4, IL-6, NE, and NSE levels showed significant differences among the critical, severe, and common groups before and after treatment (P<0.01). No significant differences in AQP-4 levels in cerebrospinal fluid (CSF) were observed between the critical and severe groups before and after treatment, but the CSF AQP-4 levels in these two groups were higher than those in the common group before treatment (P<0.01). Serum AQP-4 levels, but not CSF AQP-4 levels, closely correlated with serum IL-6, NE, and NSE levels. These results suggest that the level of AQP-4 in serum, but not in CSF, is a candidate biomarker for evaluating the severity and prognosis of EV71-associated HFMD.

Cellular distribution of aquaporins in testes of normal and cryptorchid dogs: A preliminary study on dynamic roles

Fluid regulation within the male gonad is an important process for promoting sperm differentiation and maturation. Aquaporins (AQPs) are a family of thirteen integral membrane proteins involved in these processes. The expression of several genes of AQPs occurs in the male reproductive tract of humans and other animal species, although there are few studies on domestic animals. In this study, the localization of AQP7, AQP8, and AQP9 as well as the abundances of protein and mRNA transcripts were examined in normal and cryptorchid dog testes. There was immunohistochemical localization of AQP7, AQP8, and AQP9 in both the tubular and interstitial compartments of the normal and retained testes and crytorchid dogs, albeit there was an obvious difference in cellular localization with the testes from the cryptorchid dogs. These results were supported by western blotting and real-time RT-PCR analyses, there was a lesser AQP7 and greater AQP9 abundance of protein and mRNA transcripts in the cryptorchid testis. These findings indicate combined testicular functions of AQPs in cell volume regulation. In addition, with the cryptorchid condition characterized there was a different cellular distribution of AQPs supporting the thought that early detection is important for controlling possible side effects of cyptorchidism, such as pre-neoplastic and carcinogenic outcomes.

Localization of orexin B and orexin-2 receptor in the rat epididymis

The peptides orexin A (OXA) and orexin B (OXB) derived from the proteolytic cleavage of a common precursor molecule, prepro-orexin, were originally described in the rat hypothalamus. Successively, they have been found in many other brain regions as well as in peripheral organs of mammals and other less evolved animals. The widespread localization of orexins accounts for the multiple activities that they exert in the body, including the regulation of energy homeostasis, feeding, metabolism, sleep and arousal, stress, addiction, and cardiovascular and endocrine functions. Both OXA and OXB peptides bind to two G-coupled receptors, orexin-1 (OX1R) and orexin-2 (OX2R) receptor, though with different binding affinity. Altered expression/activity of orexins and their receptors has been associated with a large number of human diseases. Though at present evidence highlighted a role for orexins and cognate receptors in mammalian reproduction, their central and/or local effects on gonadal functions remain poorly known. Here, we investigated the localization of OXB and OX2R in the rat epididymis. Immunohistochemical staining of sections from caput, corpus and cauda segments of the organ showed intense signals for both OXB and OX2R in the principal cells of the lining epithelium, while no staining was detected in the other cell types. Negative results were obtained from immunohistochemical analysis of hypothalamic and testicular tissues from OX2R knock-out mice (OX2R^-/-) and OX1R/OX2R double knock-out (OX1R^-/-; OX2R^-/-) mice, thus demonstrating the specificity of the rabbit polyclonal anti-OX2R antibody used in our study. On contrary, the same antibody clearly showed the presence of OX2R in sections from hypothalamus and testis of normal mice and rats which are well known to express the receptor. Thus, our results provide the first definite evidence for the immunohistochemical localization of OXB and OX2R in the principal cells of rat epididymis.

Effects of orexins on 17β-estradiol synthesis and P450 aromatase modulation in the testis of alpaca (Vicugna pacos)

The steroidogenic enzyme P450 aromatase (ARO) has a key role in the conversion of testosterone (T) into estrogens (E), expressed as 17β-estradiol. The presence and localization of this key enzyme have not been described before in the South American camelid alpaca (Vicugna pacos). In our previous studies of the expression and biological effects of orexin A (OxA) and OxB on the alpaca testis demonstrated that OxA, via its specific receptor 1 (OX1R), stimulated T synthesis. In order to extend these findings, we presently explored the presence and localization of ARO in the alpaca male gonad, and the possible correlation between ARO and the orexinergic complex. Western blotting and immunohistochemistry demonstrated the presence of ARO in tissue homogenates and its localization in the tubular and interstitial compartments of the alpaca testis, respectively. The addition of OxA to fresh testicular slices decreased the 17β-estradiol E levels. This effect was annulled by the sequential addition of the selective OX1R antagonist, SB-408124. OxB incubation did not have any effect on the biosynthesis of E. Furthermore, the OxA-mediated down-regulation of E secretion could be ascribed to ARO inhibition by exogenous OxA, as indicated by measurement of ARO activity in tissue slices incubated with OxA. Overall, our findings suggest that locally secreted OxA interacting with OX1R could indirectly inhibit ARO activity, disabling the conversion of T to E, and consequently lowering E biosynthesis and increasing the production of T in mammalian testis.

New Perspectives on the Potential Role of Aquaporins (AQPs) in the Physiology of Inflammation

Aquaporins (AQPs) are emerging, in the last few decades, as critical proteins regulating water fluid homeostasis in cells involved in inflammation. AQPs represent a family of ubiquitous membrane channels that regulate osmotically water flux in various tissues and sometimes the transport of small solutes, including glycerol. Extensive data indicate that AQPs, working as water channel proteins, regulate not only cell migration, but also common events essential for inflammatory response. The involvement of AQPs in several inflammatory processes, as demonstrated by their dysregulation both in human and animal diseases, identifies their new role in protection and response to different noxious stimuli, including bacterial infection. This contribution could represent a new key to clarify the dilemma of host-pathogen communications, and opens up new scenarios regarding the investigation of the modulation of specific AQPs, as target for new pharmacological therapies. This review provides updated information on the underlying mechanisms of AQPs in the regulation of inflammatory responses in mammals and discusses the broad spectrum of options that can be tailored for different diseases and their pharmacological treatment.

Computing osmotic permeabilities of aquaporins AQP4, AQP5, and GlpF from near-equilibrium simulations

Measuring or computing the single-channel permeability of aquaporins/aquaglyceroporins (AQPs) has long been a challenge. The measured values scatter over an order of magnitude but the corresponding Arrhenius activation energies converge in the current literature. Osmotic flux through an AQP was simulated as water current forced through the channel by kilobar hydraulic pressure or theoretically approximated as single-file diffusion. In this paper, we report large scale simulations of osmotic current under sub M gradient through three AQPs (water channels AQP4 and AQP5 and glycerol-water channel GlpF) using the mature particle mesh Ewald technique (PME) for which the established force fields have been optimized with known accuracy. These simulations were implemented with hybrid periodic boundary conditions devised to avoid the artifactitious mixing across the membrane in a regular PME simulation. The computed single-channel permeabilities at 5°C and 25°C are in agreement with recently refined experiments on GlpF. The Arrhenius activation energies extracted from our simulations for all the three AQPs agree with the in vitro measurements. The single-file diffusion approximations from our large-scale simulations are consistent with the current literature on smaller systems. From these unambiguous agreements among the in vitro and in silico studies, we observe the quantitative accuracy of the all-atom force fields of the current literature for water-channel biology. We also observe that AQP4, that is particularly rich in the central nervous system, is more efficient in water conduction and more temperature-sensitive than other water-only channels (excluding glycerol channels that also conduct water when not inhibited by glycerol).

Expression, Distribution and Role of Aquaporin Water Channels in Human and Animal Stomach and Intestines

Stomach and intestines are involved in the secretion of gastrointestinal fluids and the absorption of nutrients and fluids, which ensure normal gut functions. Aquaporin water channels (AQPs) represent a major transcellular route for water transport in the gastrointestinal tract. Until now, at least 11 AQPs (AQP1–11) have been found to be present in the stomach, small and large intestines. These AQPs are distributed in different cell types in the stomach and intestines, including gastric epithelial cells, gastric glands cells, absorptive epithelial cells (enterocytes), goblet cells and Paneth cells. AQP1 is abundantly distributed in the endothelial cells of the gastrointestinal tract. AQP3 and AQP4 are mainly distributed in the basolateral membrane of epithelial cells in the stomach and intestines. AQP7, AQP8, AQP10 and AQP11 are distributed in the apical of enterocytes in the small and large intestines. Although AQP-null mice displayed almost no phenotypes in gastrointestinal tracts, the alterations of the expression and localization of these AQPs have been shown to be associated with the pathology of gastrointestinal disorders, which suggests that AQPs play important roles serving as potential therapeutic targets. Therefore, this review provides an overview of the expression, localization and distribution of AQPs in the stomach, small and large intestine of human and animals. Furthermore, this review emphasizes the potential roles of AQPs in the physiology and pathophysiology of stomach and intestines.

Aquaporins in Health and Disease: An Overview Focusing on the Gut of Different Species

Aquaporins (AQPs) play a pivotal role in gut homeostasis since their distribution and function is modulated both in physiological and in pathophysiological conditions. The transport of water and solutes through gut epithelia is essential for osmoregulation and digestive and absorptive functions. This passage is regulated by different AQP isoforms and characterized by their peculiar distribution in the gastrointestinal tract. To date, AQP localization has been identified in the gut and associated organs of several mammalian species by different techniques (immunohistochemical, western blotting, and RT-PCR). The present review describes the modulation of AQP expression, distribution, and function in gut pathophysiology. At the same time, the comparative description of AQP in animal species sheds light on the full range of AQP functions and the screening of their activity as transport modulators, diagnostic biomarkers, and drug targets. Moreover, the phenotype of knockout mice for several AQPs and their compensatory role and the use of specific AQP inhibitors have been also reviewed. The reported data could be useful to design future research in both basic and clinical fields.