The recovery of some components of the renin angiotensin system in the rat pancreas after chronic exposure to hypoxic condition

Previous studies have shown that the expression of the major components from a local pancreatic renin-angiotensin system (RAS) was upregulated after chronic exposure to oxygen deprivation (10% oxygen). In the present study, the reversibility of expression for the pancreatic RAS affected by chronic hypoxia was investigated in the pancreas. Rats were first subject to hypoxia for one Month and they were then returned to normoxic conditions for a varying period of time (1, 2, 3 and 4 weeks). The degree of recovery in the expression of RAS components was analyzed with standard curve-quantitative competitive-reverse transcription-polymerase chain reaction (SC-QC-RT-PCR), Western blot analysis and a specific assay for angiotensin-converting enzyme (ACE) activity. Results from SC-QC-RT-PCR showed that the upregulated expression of angiotensin II type 1 (AT(1)) receptor mRNA following chronic hypoxia could be completely restored to the control level after the rats were returned to the normoxic condition for 3 weeks. The reversibility of mRNA expression for angiotensin II type 2 (AT(2)) receptor and angiotensinogen was observed after the return to normoxic conditions for 2 and 3 weeks respectively when compared with that of their respective controls. Results from Western blot analysis further confirmed that the expression of AT(1) receptor protein was also reversible after return to normoxic conditions for 4 weeks. In addition, the activation of ACE activity returned to its normal level in a time-dependent manner. These data indicate that the upregulation of a local pancreatic RAS affected by chronic hypoxia could be recoverable. The significance of its reversibility and adaptability following chronic hypoxia may be of physiological relevance to the pancreas.

The renin-angiotensin system and male reproduction: new functions for old hormones

The blood-borne renin-angiotensin system (RAS) is known best for its role in the maintenance of blood pressure and electrolyte and fluid homeostasis. However, numerous tIssues show intrinsic angiotensin-generating systems that cater for specific local needs through actions that add to, or differ from, the circulating RAS. The male reproductive system has several sites of intrinsic RAS activity. Recent focus on the epididymis, by our laboratories and by others, has contributed important details about the local RAS in this tIssue. The RAS components have been localized morphologically and topographically; they have been shown to be responsive to androgens and to hypoxia; and angiotensin has been shown to influence tubular, and consequently, fluid secretion. Components of the RAS have also been found in the testis, vas deferens, prostate and semen. Angiotensin II receptors, type 1 and, to a lesser extent, type 2 are widespread, and angiotensin IV receptors have been localized in the prostate. The roles of the RAS in local processes at these sites are still uncertain and have yet to be fully elucidated, although there is evidence for involvement in tubular contractility, spermatogenesis, sperm maturation, capacitation, acrosomal exocytosis and fertilization. Notwithstanding this evidence for the involvement of the RAS in various important aspects of male reproduction, there has so far been a lack of clinical evidence, demonstrable by changes in fertility, for a crucial role of the RAS in male reproduction. However, it is clear that there are several potential targets for manipulating the activity of the male reproductive system by interfering with the locally generated angiotensin systems.

Expression, immunolocalization, and functional activity of Na+/H+ exchanger isoforms in mouse endometrial epithelium

The luminal fluid microenvironment of the uterus is important for sperm capacitation and embryo development. In an attempt to understand the possible role of Na(+)/H(+) exchangers (NHEs) in uterine function, the mRNAs of different NHE isoforms as well as their subcellular localization (apical versus basolateral) and functional activity were investigated in mouse endometrial epithelial cells using reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry, and intracellular pH (pH(i)) measurement techniques. The presence of NHE1, NHE2, and NHE4, but not NHE3 mRNAs were revealed by RT-PCR. Immunostaining showed that NHE1, NHE2, and NHE4 were present in both apical and basolateral membranes. The pH(i) recovery from intracellular acidification was Na(+)-dependent; however, the rate of pH(i) recovery depending on basolateral Na(+) was 12.4 times faster than that depending on apical Na(+). The Na(+)-dependent rate of pH(i) recovery was also inhibited by amiloride, indicating H(+) extrusion through NHEs; however, the amiloride sensitivity of the apical membrane was less than that of the basolateral membrane, suggesting the involvement of different types of NHEs in the two membranes. The results indicate that the basolaterally located NHE1, NHE2, and NHE4, in addition to participating in the homeostatic control of intracellular pH, may play a role in H(+) extrusion in order to achieve transepithelial HCO(3)(-) secretion. The apically located NHEs may be involved in mediating Na(+) absorption as alternatives of or complementary to epithelial Na(+) channels.

Effect of chronic hypoxia on glutathione status and membrane integrity in the pancreas

BACKGROUND

Our recent study has shown that chronic hypoxia could upregulate significantly a local renin-angiotensin system in the pancreas. The activation of such a local renin-angiotensin system may provide an alternate mechanism that leads to the generation of reactive radical species in the pancreas during chronically hypoxic exposure. The present study aims at elucidating the antioxidant status in the pancreas during varying degrees of chronic hypoxia.

METHODS

Sprague-Dawley rats were exposed to an isobaric hypoxic (10% oxygen) chamber for a period up to 28 days. The glutathione status and membrane integrity of the pancreas were studied with a time course of chronic hypoxia (3, 7, 14, 21 and 28 days). The effect of chronic hypoxia on changes of oxidative states in the pancreas was assessed based on the measurements of glutathione, malondialdehyde, alpha-amylase and DNA fragmentation using biochemical assays.

RESULTS

Pancreatic glutathione was decreased drastically after 3-day hypoxia and its level was almost completely recovered after 7-day hypoxia. Malondialdehyde was not affected while DNA fragmentation was increased significantly in a time-dependent manner during the course of chronic hypoxia. Membrane integrity of the pancreatic cells was improved, as evidenced by the decrease of plasma alpha-amylase during the time-course study of chronic hypoxia.

CONCLUSION

Pancreatic glutathione was depleted only in the early period of chronic hypoxia followed by a rapid recovery, suggesting that adaptive response of the pancreas may occur during chronic hypoxia. The enhancement of glutathione-dependent antioxidant capacity during chronic hypoxia prevented oxidative damage to the membrane of the pancreatic cells.

Intrinsic angiotensin-generating system: its tissue specific functions and clinical implications

The classical hormone angiotensin II is derived from the circulating renin-angiotensin system (RAS), which has a crucial role in the regulation of cardiovascular function, electrolyte as well as water homeostasis. In addition, numerous tissues/organs possess their own intrinsic, angiotensin-generating systems that meet the needs specific for individual tissues/organs. The machinery could be operated through the actions that add to, and/or differ from, the circulating RAS. Of particular interest in this context is the existence of an intrinsic RAS in such tissues as the pancreas, epididymis and carotid body. There has been a steady stream of evidence to suggest that these intrinsic RAS may have potential roles in the maintenance of their tissue/organ specific functions. More intriguingly, alterations of such an intrinsic RAS could be associated with the physiological and pathophysiological aspects of the respective tissue/organ functions. Future targets for the intervention of the intrinsic RAS, such as at the levels of pancreas, epididymis and carotid body should have clinical implications for the management of their respective functions.

Renin-angiotensin system expression and secretory function in cultured human ciliary body non-pigmented epithelium

BACKGROUND

Renin-angiotensin system (RAS) components have been identified in human ciliary body and aqueous humour, pointing to a role for the RAS in the regulation of aqueous humour dynamics. Here, the authors examine the functional expression of a RAS and the effects of angiotensin II (AII) on a signal transduction pathway and ion secretion mechanism in cultured human ciliary body non-pigmented epithelium (HNPE).

METHODS

RAS expression was examined in cultured HNPE cells using polymerase chain reaction (PCR) analysis. Secretory function was determined using spectrofluorescence imaging microscopy to measure cell calcium (Ca(2+)(I)) and volume responses. Single channel patch clamp techniques were employed to investigate ion channel activity.

RESULTS

PCR analysis demonstrated the expression of angiotensinogen and the AT(1b) receptor in HNPE cells. A large conductance potassium (BK) channel (mean 190 (SEM 5.6) pS, n = 22 cells), was observed in plasma membrane patches. This channel was calcium sensitive with channel open probability (Po) increasing with increasing Ca(2+)(I) (K(0.5) 10.79 (0.44) microM Ca(2+), Hill coefficient of 1.04 (0.04)). AII (100 nM) increased the number (N) of active BK channels in HNPE cells and also the probability of channel opening (Po). N.P(o) increased from 0.008 (0.002) to 1.38 (0.4) following the addition of AII (p=0.0064). AII also induced a rapid rise in Ca(2+)(I) from resting values of 112 (14) nM to a peak of 992 (106) nM (p<10(-4)). A simultaneous cell volume reduction of 24.70% (3.34%) (p<10(-4)) occurred during this calcium signal. Losartan (1 microM) significantly blocked the AII induced BK channel activation (p=0.0131), the Ca(2+)(I) response (p<10(-4)), and the AII induced volume effect (p=0.0046).

CONCLUSION

It was demonstrated that AII activates a Ca(2+)(I) signalling system which subsequently increases potassium ion channel activity. These effects are accompanied simultaneously by cell volume loss, indicating that AII acts as receptor operated secretagogue in HNPE cells. The ability of an AT(1) receptor antagonist to inhibit these processes may thus offer a new family of pharmaceutical agents to the current armamentarium in the treatment of glaucoma.

Androgen dependent expression of AT1 receptor and its regulation of anion secretion in rat epididymis

Our previous studies have provided solid evidence for the presence of an intrinsic angiotensin-generating system in the rat epididymis, which plays an important role in the regulation of the anion and thus fluid secretion by the epididymal epithelium. In the present study, the effect of androgen on the expression of AT(1)receptor and its subsequent regulation of anion secretion by the epididymis were investigated using Western blotting, semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and in vitro electrophysiological approaches. Results from Western blotting analysis showed that the expression of AT(1)receptor protein was almost abolished by castration whereas its expression was completely restored to the control level when the castrated rats were hormonally replaced with testosterone. Efferent duct ligation, however, appeared not to affect the expression of AT(1)receptor protein by the epididymis. Results from RT-PCR showed that mRNA expression of AT(1)receptor was consistent with that observed in protein expression. Results from short-circuit current (I(SC)) showed that castration almost abolished the angiotensin II-induced I(SC). However, efferent duct ligation did not affect the angiotensin II-induced I(SC), which was completely blocked in the presence of losartan, a specific antagonist of the AT(1)receptor. These data indicate that the expression of epididymal AT(1)receptor is predominantly influenced by testicular androgens but not by testicular factors. This androgen-dependent expression of AT(1)receptor could have a role in the control of AT(1)receptor-mediated anion secretion and thus fluid secretion by the rat epididymis.

Postnatal hypoxemia increases angiotensin II sensitivity and up-regulates AT1a angiotensin receptors in rat carotid body chemoreceptors

In the present study, the effects of postnatal hypoxemia on the AT1 angiotensin receptor-mediated activities in the rat carotid body were studied. Angiotensin II (Ang II) concentration-dependently increased the chemoreceptor afferent activity in the isolated carotid body. Single- or pauci-fiber recording of the sinus nerve revealed that the afferent response to Ang II was enhanced in the postnatally hypoxic carotid body. To determine whether the increased sensitivity to Ang II is mediated by changes in the functional expression of Ang II receptors in the carotid body chemoreceptors, cytosolic calcium ([Ca2+]i) was measured by spectrofluorimetry in fura-2 acetoxymethyl ester-loaded type I cells dissociated from carotid bodies. Ang II (25-100 nM) concentration-dependently increased [Ca2+]i in the type I cells. The proportion of clusters of type I cells responsive to Ang II was higher in the postnatally hypoxic group than in the normoxic control (89 vs 66%). In addition, the peak [Ca2+]i response to Ang II was enhanced 2- to 3-fold in the postnatally hypoxic group. The [Ca2+]i response to Ang II was abolished by pretreatment with losartan (1 microM), an AT1 receptor antagonist, but not by PD-123177 (1 microM), an AT(2) antagonist. Double-labeling immunohistochemistry confirmed that an enhanced immunoreactivity for AT1 receptor was co-localized to the lobules of type I cells in the hypoxic group. In addition, RT-PCR analysis of subtypes of AT1 receptors showed an up-regulation of AT1a but a down-regulation of AT1b receptors, indicating a differential regulation of the expression of AT1 receptor subtypes by postnatal hypoxia in the carotid body. These data suggest that postnatal hypoxemia is associated with an increased sensitivity of peripheral chemoreceptors in response to Ang II and an up-regulation of AT1a receptor-mediated [Ca2+]i activity of the chemoreceptors. This modulation may be important for adaptation of carotid body functions in the hypoxic ventilatory response and in electrolyte and water homeostasis during perinatal and postnatal hypoxia.

The upregulation of angiotensin II receptor AT(1) in human preeclamptic placenta

The human placenta has been considered to possess a locally generated renin-angiotensin system (RAS), which may play a physiological role in the regulation of uteroplacental blood circulation. The changes in the expression of such a placental RAS during pregnancy could be important for the physiological and pathophysiological aspects of some clinical disorders, such as pregnancy-induced hypertension, preeclampsia. In the present study, the alterations of expression and localization of placental angiotensin II receptor subtypes, namely AT(1) in patients with preeclampsia (elective caesarean delivery) were investigated and compared with controls (vaginal delivery and elective caesarian delivery) using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), Western blot and immunohistochemistry respectively. Results from RT-PCR analysis revealed an upregulated expression of placental mRNA for AT(1) receptor subtype in patients with preeclampsia when compared with those in controls. In addition, there was also a significant activation of placental expression of angiotensinogen mRNA in patients with preeclampsia. Results from Western blot showed that the expression of AT(1) receptor was also upregulated. Immunohistochemical results further demonstrated that increased immunoreactivity for placental AT(1) receptor was predominantly localized to the thin layers of syncytiotrophoblasts and, to a less extent, the capillaries of the term placental villi. These data indicate that upregulation of placental RAS components, notably AT(1) receptor in the syncytiotrophoblasts, could play a pathophysiological role in patients with preeclampsia.

Immunoglobulin gene usage and immunohistochemical characteristics of human monoclonal antibodies to the mitochondrial autoantigens of primary biliary cirrhosis induced in the XenoMouse

The immunodominant antimitochondrial antibody (AMA) response in primary biliary cirrhosis (PBC) is directed against the E2 component of pyruvate dehydrogenase (PDC-E2). The nature of the clonal selection process is unclear, and to address this issue, we took advantage of a transgenic technology, XenoMouse, that contains 80% of the human immunoglobulin (Ig) variable gene repertoire and can produce high-affinity human antibodies to virtually any immunogen without evidence of clonal bias. We immunized mice with PDC-E2 to obtain 13 HmAbs, including 4 IgG(2) and 9 IgM isotypes. Immunoglobulin gene analysis was unique and demonstrated a clonal bias; the immunoglobulin gene usage was considerably different from other antibody responses analyzed in XenoMouse systems. Four of the 13 mAbs recognized the inner lipoyl domain of PDC-E2, 2 of 13 recognized the entire PDC-E2 molecule, 4 of 13 recognized PDC-E2 and OGDC-E2, 1 of 13 recognized OGDC only, 1 recognized BCOADC-E2 only, and 1 recognized an unidentified 100-kd mitochondrial protein. Immunohistochemical staining using these HmAbs produced mitochondrial staining of septal bile ducts in both PBC and control livers. Ig gene analysis showed that 7 of 13 HmAbs used the V(H)3 and 4 of 13 used VH4 gene repertoire, respectively. Three of 7 V(H)3 antibodies used the same Ig VH3-21 gene family found in human AMA from patients with PBC. The CDRs of these autoantibodies were slightly mutated when compared with the sequences present within the Ig germline genes. In conclusion, the XenoMouse not only recapitulates the unique specificity and restriction of PBC patients, but indicates that the autoantibodies are derived from a restricted clonal selection process. Such data suggest that the original immunogen leads to somatic mutation without subsequent development of determinant spreading.

Secretin facilitates GABA transmission in the cerebellum

Secretin was the first hormone discovered in human history, and yet, its function as a neuropeptide has been overlooked in the past. The recent discovery of the potential use of secretin in treating autistic patients, together with the conflicting reports on its effectiveness, urges an in-depth investigation of this issue. We show here that in the rat cerebellar cortex, mRNAs encoding secretin are localized in the Purkinje cells, whereas those of its receptor are found in both Purkinje cells and GABAergic interneurons. Immunoreactivity for secretin is localized in the soma and dendrites of Purkinje cells. In addition, secretin facilitates evoked, spontaneous, and miniature IPSCs recorded from Purkinje cells. We propose that secretin is released from the somatodendritic region of Purkinje cells and serves as a retrograde messenger modulating GABAergic afferent activity.

Expression of bacterial beta-glucuronidase in human bile: an in vitro study

BACKGROUND

Bacterial beta-glucuronidase causes deconjugation of bilirubin diglucuronide resulting in the precipitation of calcium bilirubinate, which contributes to biliary sludge and stone formation. This process is attributed to enzyme activity produced by the aerobic enterobacteriaceae such as Escherichia coli and Klebsiella sp. The presence of Clostridium sp. was detected in 48 of 56 intrahepatic stones by using polymerase chain reaction techniques and cultured Clostridium perfringens from 14 of 18 unblocked biliary stents. Such bacteria are reported to produce beta-glucuronidase activity. The aim of this study was to determine the proportion of biliary bacteria isolated from pigment stones and stents that produce beta-glucuronidase and to compare the enzyme activity expressed by the different bacteria in human bile.

METHODS

A total of 202 bacteria were isolated from blocked and unblocked biliary stents and pigment ductal stones recovered from patients. Of these, 61 bacteria expressed beta-glucuronidase activity in brain heart infusion broth. These 61 bacteria were subsequently grown in human bile under aerobic or anaerobic conditions to the early stationary phase and assayed for beta-glucuronidase activity by using rho-nitrophenyl beta-D glucuronide as substrate. Results were normalized and reported as units of enzyme activity per milligram protein of the bacteria.

RESULTS

C. perfringens produced beta-glucuronidase enzyme activity that was 34-fold higher than that for E coli, Staphylococcus, Corynebacterium sp., Bacillus sp., Enterococcus sp., Acinetobacter sp., Streptococcus sp., and Klebsiella sp.

CONCLUSION

C. perfringens with its higher enzyme activity is more important in the deconjugation of bilirubin diglucuronide than E coli and Klebsiella sp.

Genomic analysis of differentially expressed genes in liver and biliary epithelial cells of patients with primary biliary cirrhosis

The characterization of differentially expressed genes provides a powerful tool for identifying molecules that may be involved in the pathogenesis of disease. We have used two independent techniques to identify overexpressed transcripts in bile duct cells and in liver from patients with primary biliary cirrhosis (PBC). In the first method, we used suppressive subtractive hybridization to compare mRNA from isolated PBC bile duct epithelial cells (BECs) to normal BECs and identified 71 clones as transcribed at higher levels in PBC-BECs. Amongst these clones, 62/71 had matches in a non-redundant nucleotide database and 9/71 had matches in an EST database. Of the 62 clones, 51/62 include a complexity of genes involved in cell proliferation, signal transduction, transcription regulation, RNA processing, carbohydrate metabolism and hypothetical/unknown proteins; 4/62 were identified as interstitial collagenase and collagenase precursors, 4/62 as ribosomal proteins, 3/62 as mitochondrial DNA. The mitochondrial cDNA sequences included cytochrome c oxidase, Wnt-13, and the pHL gene, a c-myc oncogene containing coxIII sequence. In the second method, we constructed cDNA libraries from three different PBC livers and sequenced a total of 12,324 independent clones. These 12,324 clones underwent virtual subtraction with 2,814,148 independent clones from Incyte LifeSeq libraries. Twenty one sequences were identified as unique to PBC liver. Collectively, these approaches identified a number of genes involved in signalling, RNA processing, mitochondrial function, inflammation, and fibrosis. Interestingly, both Wnt-13 and Notch transcripts are overexpressed in PBC liver. Further studies are needed to focus on the significance of these genes during the natural history of disease.

cDNA cloning and molecular identification of the major oyster allergen from the Pacific oyster Crassostrea gigas

BACKGROUND

Shellfish is one of the most common food allergens. Despite the recent cloning and molecular identification of the major heat stable crustacean allergens in shrimp, lobster and crab, there have been no similar studies on molluscs to which a significant portion of populations allergic to shellfish are also hypersensitive. Recent biochemical evidence suggests that tropomyosin is also an allergen in molluscs, but data on the molecular cloning, nucleotide sequencing, expression and IgE binding to mollusc tropomyosin are lacking.

OBJECTIVE

This study was undertaken to clone, identify and determine the primary structure of a major IgE-reactive mollusc allergen in oyster at the DNA and protein level.

METHODS

We constructed an expression cDNA library from the Pacific oyster Crassostrea gigas. This library was screened for IgE binding clones using sera from 15 subjects with a well-documented history of type I hypersensitivity reactions to oysters. An IgE reactive clone was selected and sub-cloned into plasmids for nucleotide sequence determination and expression in E. coli.

RESULTS

We identified a 1.3-kb cDNA designated as Cra g 1.03. Expression of Cra g 1.03 in plasmid vector pGEX produced a 59-kDa recombinant fusion protein reactive to the IgE antibodies from patients with oyster allergies but not non-allergic controls. Cra g 1.03 has an open reading frame of 233 amino acids and demonstrates marked similarity in amino acid composition and peptide sequence with mollusc and crustacean tropomyosins. Absorption of oyster allergic sera with Cra g 1.03 totally removed IgE reactivity to oyster extract. Moreover, absorption of allergic sera with recombinant shrimp tropomyosin (Met e 1), lobster tropomyosin (Pan s 1) and crab tropomyosin (Cha f 1) removed most of the IgE reactivity to Cra g 1.03.

CONCLUSION

Cra g 1.03 is the first oyster allergen identified at the molecular level. Nucleotide and amino acid comparison shows that this protein is the oyster tropomyosin.

Fragment of Japanese encephalitis virus envelope protein produced in Escherichia coli protects mice from virus challenge

A fragment from the N-terminal part (E(A)) and a fragment from the C-terminal part (E(B)) of the envelope (E) protein of Japanese encephalitis virus (JEV) was synthesized in Escherichia coli. These two fragments were overlapping with each other by nine amino acids, however, they were not cross-reacting with each other at the antisera level. Both E(A)and E(B)are antigenic by themselves when injected into mice, but when tested against sera from mice, rabbit, swine and human that had been immunized or naturally infected with JEV, E(B)acted as a better antigen than E(A)by ELISA assays. E(B)also proved to be a better immunogen in protection against lethal JEV infection than E(A). The protection appears to be correlated with the neutralizing titres of the anti-JEV sera. The response elicited by E(B)is a Th1 response and the antibody produced contained higher neutralizing titre than E(A)fragment. The major difference between E(A)and E(B)fragments is the solubility during expression in E. coli, while E(B)fragment is soluble, E(A)was isolated from the insoluble inclusion bodies. Therefore the antigenicity and immunogenicity expressed by the E(B)fragment may probably be due to its proper folding to assume a correctly assembled form during expression in E. coli, a quality that is important for a protein to qualify as a good vaccine candidate.

Tissue renin-angiotensin system: its expression, localization, regulation and potential role in the pancreas

The classical concept of the renin-angiotensin system (RAS) is that of a blood-borne cascade, whose final and bioactive product, angiotensin II, plays an important endocrine role in the maintenance of blood pressure and electrolyte as well as fluid balance. In addition to this circulating RAS, there are an increasing number of studies to suggest the existence of a local angiotensin-generating system in several tissues. The so-called tissue RAS can act locally as a paracrine and/or autocrine factor in meeting specific needs for individual tissues and it can operate, in whole or in part, independently of the circulating counterpart. Recent studies on the expression and localization of key RAS components, particularly angiotensinogen and renin, have provided solid evidence for the existence of an intrinsic, angiotensin-generating system in the pancreas. The tissue RAS has a potential role in finely regulating exocrine and endocrine functions of the pancreas such as ductal anion secretion and islet hormonal secretion. Some of these effects may be exerted via the markedly vasoconstrictive effects of RAS. Of particular interest in this context are the recent epidemiological data showing that administration of angiotensin-converting enzyme inhibitors appears to be protective against the development of diabetes in hypertensive patients. Moreover, the upregulation of pancreatic RAS has been shown to occur during chronic hypoxia. The significance of changes in pancreatic RAS could have a potential role in acute pancreatitis, islet transplantation and in different shock states, by causing a further decrease of blood perfusion in the pancreas.

Local regulation of anion secretion by pituitary adenylate cyclase-activating polypeptide in human colonic T84 cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a novel hypothalamic peptide, which has been shown to exert various functions in a number of tissues, including exocrine and endocrine tissues. The present study investigated the role of local PACAP in the control of anion secretion by the human colonic T84 cell. Both bioactive forms of PACAP-27 and PACAP-38 gave rise to a dose-dependent increase in the short-circuit current (I(SC)). However, there was a reversal in the order of potency observed at different concentration ranges for the two bioactive forms. PACAP-27 was greater than PACAP-38 when the peptide concentrations were below 10 n m; PACAP-38 was greater than PACAP-27 in the range of 10-80 n m. The effects of both PACAP forms were restricted to the apical aspect of the T84 cell. The I(SC)responses to both PACAP-27 and PACAP-38 were suppressed respectively by the non-selective Cl(-)channel blocker, diphenylamine-dicarboxylic acid (DPC), by the Ca(2+)dependent Cl(-)channel blocker, diisothiocyanatostilbene-disulfonic acid (DIDS) and by the Ca(2+)chelator, BAPTA-AM, indicating the involvement of Ca(2+). The expression of PACAP was demonstrated and localized specifically to the perinuclear cytoplasm of the T84 cell using immunocytochemistry, indicating its epithelial origin. Thus, the present data suggest that, in addition to the well-known cAMP-dependent pathway, PACAP may play a role in regulating colonic Cl(-)secretion via a Ca(2+)-dependent pathway, perhaps through two distinct PACAP receptor subtypes. Moreover, the regulation of anion secretion by T84 cells may be mediated by locally formed PACAP in an autocrine or paracrine fashion.

Chronic hypoxia induced down-regulation of angiotensinogen expression in rat epididymis

The presence of an intrinsic renin-angiotensin system (RAS) in the rat epididymis has been previously established by showing the expression of several key RAS components, and in particular angiotensinogen, the indispensable element for the intracellular generation of angiotensin II. In this study, the possible involvement of this local epididymal RAS in the testicular effects of chronic hypoxia was investigated. Semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR), Western blotting and by in situ hybridization histochemistry of the rat epididymis were used to show changes in localization and expression of angiotensinogen. Results from RT-PCR analysis demonstrated that chronic hypoxia caused a marked decrease (60%) in the expression of angiotensinogen mRNA, when compared with that in the normoxic epididymis. Western blot analysis demonstrated a less decrease (35%) in the expression of angiotensinogen protein. In situ hybridization histochemistry showed that the reduced angiotensinogen mRNA in chronic hypoxia was specifically localized to the epididymal epithelium from the cauda, corpus and caput regions of the epididymis; a distribution similar to that of normoxic rats. It was concluded that chronic hypoxia decreases the transcriptional and translational expression of angiotensinogen, and thus local formation of angiotensin II, in the rat epididymis.

Association of free radicals and the tissue renin-angiotensin system: prospective effects of Rhodiola, a genus of Chinese herb, on hypoxia-induced pancreatic injury

The renin-angiotensin system has long been recognized as crucial factor in the regulation of the systemic blood pressure and renal electrolyte homeostasis. Numerous studies have demonstrated the presence of a local renin-angiotensin system in a variety of organs. A recent study of the pancreatic renin-angiotensin system showed that chronic hypoxia significantly increased the mRNA expression for angiotensinogen II receptor subtypes AT1b and AT2. The activation of the renin-angiotensin system may play an important role in cellular pathophysiological processes. Angiotensin II enhances the formation of reactive oxygen species via the activation of xanthine oxidase or NAD(P)H oxidase. The reactive oxygen species can cause oxidative damage in the pancreas and other tissues either directly or indirectly via the formation of other radicals such as reactive nitrogen species. Rhodiola therapy may protect hypoxia-induced pancreatic injury in two ways. It prevents hypoxia-induced biological changes by increasing intracellular oxygen diffusion and efficiency of oxygen utilization. Alternatively, it reduces hypoxia-induced oxidative damage by its antioxidant activities. Additional experimental data are required to fully elucidate the mode of action of this herbal drug.

Functional expression of angiotensin II receptors in type-I cells of the rat carotid body

Angiotensin II increases afferent discharge from the carotid body in vitro. We hypothesized that angiotensin II receptors (AT receptors) are expressed functionally in the type-I cell of the carotid body. Cytosolic free [Ca2+] ([Ca2+]i) in type-I cells freshly dissociated from rat carotid bodies was measured spectrofluorimetrically. Angiotensin II (10-100 nM) concentration-dependently increased [Ca2+]i in type-I cells. The [Ca2+]i response was blocked by pretreatment with losartan (1 microM), an AT1 receptor antagonist, but not by blockade of AT2 receptors with PD- 123319 (1 microM). Moreover, the gene expression of AT1 receptors was assessed by the reverse transcriptase polymerase chain reaction and gene transcripts of both AT1a and AT1b receptors were detected in the carotid body. In addition, immunohistochemical study revealed that AT1 immunoreactivity was localized in lobules of type-I cells in the carotid body. Taken together, these results suggest that type-I cells in the rat carotid body express functional angiotensin II receptors. The binding of angiotensin II to the AT1 receptors increases [Ca2+]i, a key step of the intracellular signalling cascade following the activation of the receptors. It is concluded that angiotensin II modulates carotid body chemoreceptor function directly via AT1 receptors in the type-I cell.

Local renin-angiotensin system in the pancreas: the significance of changes by chronic hypoxia and acute pancreatitis

The circulating renin-angiotensin system (RAS) plays an important role in the maintenance of blood pressure and fluid homeostasis. Recently, there has been a shift of emphasis from the circulating RAS to the local RAS in the regulation of individual tissue functions via a paracrine and/or autocrine mechanism. In fact, a local RAS has been proposed to be present in an array of tissues including the brain, heart, kidney and gonads. Our previous studies have provided solid evidence that several key elements of the RAS, notably angiotensinogen and renin, are present in the rat pancreas. The data support the existence of an intrinsic RAS in the pancreas and this local RAS may be important for the exocrine/endocrine functions of the pancreas. Interestingly, such a pancreatic RAS has been demonstrated to be markedly activated by experimental rat models of chronic hypoxia and acute pancreatitis. The activation of the pancreatic RAS by chronic hypoxia and experimental pancreatitis could play a role in the physiology and pathophysiology of the pancreas. The significant changes of pancreatic RAS may have clinical relevance to acute pancreatitis and hypoxia-induced injury in the pancreas.

Primary biliary cirrhosis and autoimmunity: evaluating the genetic risk

The genetic basis of autoimmunity is receiving increased attention. Organ-specific diseases, such as primary biliary cirrhosis, may be considered model diseases to use for development of databases and extrapolation to other autoimmune diseases. PBC is an enigmatic autoimmune disease that predominantly affects females and leads to destruction of intrahepatic bile ducts. The serologic hallmark of this disease is anti-mitochondrial antibodies that specifically react with the E2 components of 2-oxodehydrogenase enzymes, including PDC-E2. There are no clear major histocompatibility complex associations with the development of PBC, despite the observation that first-degree relatives of index patients with PBC have a 4-6% prevalence of development of PBC. This risk factor is comparable or higher than any other human autoimmune disease and suggests that a genome-wide approach towards dissection of genetic associations would lead to valuable new insights. In this review we place these concepts in perspective and highlight in particular the genetic associations in primary biliary cirrhosis.

Chronic hypoxia upregulates the expression and function of AT(1) receptor in rat carotid body

In the present study, the effects of chronic hypoxia on the expression and localization of angiotensin II (Ang II) receptors are investigated by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and by immunohistochemistry. The effect of chronic hypoxia on the carotid body chemoreceptor activity was also examined by in vitro electrophysiology. Results from RT-PCR revealed that chronic hypoxia exhibited differential effects on the gene expression of Ang II receptors, namely AT(1) and AT(2), in the carotid body. The mRNA expression for subtypes of the AT(1) receptor, AT(1a) and AT(1b), was significantly increased in the carotid body with chronic hypoxia. To further investigate the localization of the AT(1) receptor, an immunohistochemical study was performed. The results showed that AT(1) receptor immunoreactivity was found in lobules of glomus cells in the carotid body and the immunoreactivity was more intense in chronic hypoxia than in normoxic controls. In vitro electrophysiological studies consistently demonstrated that chronic hypoxia enhanced the AT(1) receptor-mediated excitation of carotid body chemoreceptor activity. These data suggest that chronic hypoxia upregulates the transcriptional and post-transcriptional expression of AT(1) receptors in the rat carotid body. The upregulation of the expression also enhances AT(1) receptor-mediated excitation of the carotid body afferent activity. This might be important in the modulation of cardiorespiratory functions as well as fluid and electrolyte homeostasis during chronic hypoxia.

Mucosal immunity and primary biliary cirrhosis: presence of antimitochondrial antibodies in urine

We have shown that IgA-class antimitochondrial autoantibodies (AMA) can be detected in the bile and saliva of patients with PBC, suggesting that AMA are secreted into the luminal fluid across bile ducts and salivary glands. These data prompted us to determine whether AMA of the IgA isotype may be transported across other epithelial mucosa. Therefore, we tested for the presence of AMA in the urine specimens of 83 patients with PBC and 58 non-PBC controls including healthy individuals and patients with other liver diseases. Patients enrolled in this study had no history of renal disease, and we confirmed there was less than 50 microgram/mL of protein in each of the urine specimens. Interestingly, we found that AMA were present in the urine of 71/83 (86%) of all patients with PBC and in 71/78 (91%) of patients with PBC that were serum AMA positive. In contrast, AMA were not detected in any of the 58 control urine specimens. Of particular interest, AMA of the IgA isotype was present in 57/83 (69%) of patients with PBC, and in 52 of these 57, we found secretory-type IgA. In a nested random subgroup of urine samples, the prevalence of the IgA2 AMA was 6/18 (33%), significantly lower than in matched serum samples, 13/16 (81%, P =.007). These data show that AMA of the IgA isotype is secreted into urine from the uroepithelium of patients with PBC, and support the thesis that PBC originated from either a mucosal challenge or a loss of mucosal tolerance.

Androgen control of cyclooxygenase expression in the rat epididymis

Bradykinin and a number of peptide hormones such as angiotensin, endothelin, and vasopressin stimulate anion secretion in rat epididymis via local formation of PGE(2). These effects are mediated by cyclooxygenase (COX)-1 isozyme. The present study was undertaken to assess the androgen control of COX expression in the epididymis. Adult male Sprague-Dawley rats were bilaterally castrated through a scrotal route. Reverse transcription-polymerase chain reaction was used to measure COX-1 and COX-2 mRNAs in the epididymis in normal and castrated rats. Anion secretion in epithelia grown from the epididymides of these rats was studied by the short-circuit current technique. In normal rats, COX-1 and COX-2 mRNAs were detected in the intact epididymis. Elimination of spermatozoa by the technique of efferent duct ligation or flushing out spermatozoa did not affect the expression of either enzyme in the epididymis, indicating that the epithelium, but not spermatozoa, expressed the enzymes. Castration caused a time-dependent decrease in expression of COX-1 and COX-2 mRNAs, which were partially restored upon testosterone replacement. In epithelia cultured from castrated rats, there was a complete loss of bradykinin-induced anion secretion. This effect was reversible upon testosterone replacement. Although epithelia from castrated rats did not respond to bradykinin, they could respond to cAMP, forskolin, and PGE(2) with only 20% loss of response magnitude when compared with epithelia from normal rats. These results suggest that the expression of COX-1 and COX-2 are dependent on androgen. The loss of COX-1 expression after castration correlates with the specific loss of anion secretion induced by bradykinin and possibly other hormones.

Tropomyosin Is the Major Mollusk Allergen: Reverse Transcriptase Polymerase Chain Reaction, Expression and IgE Reactivity

The complementary DNAs encoding tropomyosins of the abalone Haliotis diversicolor, the scallop Chlamys nobilis, and the mussel Perna viridis were amplified by reverse transcriptase polymerase chain reaction and thereafter cloned in plasmid vectors for expression. Immunoblot analysis showed that recombinant proteins of abalone, scallop, and mussel tropomyosin were reactive to serum IgE antibodies from subjects allergic to shellfish but not to nonallergic controls. Nucleotide and amino acid sequences of abalone, scallop, and mussel tropomyosins are highly similar (mostly > 55%) to those of crustacean allergens identified as tropomyosins. Absorption experiments showed that recombinant tropomyosins from the 3 mollusks were able to remove serum IgE reactivity against the 38-kDa tropomyosin of the organisms. These results demonstrate that tropomyosin is the major allergen among various common edible mollusks. Yet a comparison between the amino acid sequences of putative epitopes in crustaceans and mollusks suggests that the epitopes in the two groups may be distinct. Parsimony analysis of the nucleotide sequences of tropomyosin from different mollusks suggests that the tropomyosin gene sequence is a useful tool for phylogenetic analysis of this group of animals.

Regulated expression of pancreatic renin-angiotensin system in experimental pancreatitis

Our previous studies have provided evidence for the existence of an intrinsic renin-angiotensin system (RAS) in the rat pancreas, which may play a role in the regulation of pancreatic microcirculation and ductal secretion. Such a pancreatic RAS has recently shown to be activated by chronic hypoxia. The activation of a local RAS in the pancreas by chronic hypoxia and its significance of changes may be important for the physiological and pathophysiological aspects of the pancreas. In the present study, the regulation of experimentally induced acute pancreatitis on the expression of local RAS in the pancreas was investigated using Western blot, semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical approaches. Results from Western blot demonstrated that experimentally induced pancreatitis caused significantly increased expression of the pancreatic RAS component proteins. In keeping with the protein level, RT-PCR analysis also revealed the enhanced expression of pancreatic RAS genes, notably the angiotensinogen in experimental pancreatitis. Immunohistochemical results further demonstrated that increased immunoreactivity for RAS in experimental pancreatitis was predominantly localized to the endothelia and epithelia of pancreatic vasculature and ductal system respectively. The data indicate that experimental pancreatitis may elicit activation of a local RAS in the pancreas. Such an activation of pancreatic RAS and its significance of differential changes in individual RAS components could play a role in the pathophysiology of acute pancreatitis

Comparative immunoreactivity of anti-trifluoroacetyl (TFA) antibody and anti-lipoic acid antibody in primary biliary cirrhosis: searching for a mimic

Previous studies documenting the existence of cross-reactivity between the lipoated (but not unlipoated) forms of the inner lipoyl domain (E2L2) of PDC-E2 [the major autoantigen in Primary biliary cirrhosis (PBC)] and trifluoroacetylated (TFA) proteins, led us to hypothesize that PBC may be due to an initial insult with an environmental agent that cross-reacts with TFA. Therefore, we performed a comparative study of the reactivity of rabbit anti-TFA antibody and anti-lipoic acid (LA) antibody against the mitochondrial autoantigens of human PBC and various TFA and LA conjugated proteins. Whereas both anti-TFA and anti-LA reacted with PDC-E2, the wild-type lipoated form of E2L2, OGDC-E2, E3-BP and LA-KLH, neither reacted with BCOADC-E2 or the non-lipoated form of E2L2. Of interest was that while anti-TFA reacted with PDC-E2, TFA-RSA and LA-KLH, it failed to inhibit PDC-E2 enzyme function. In contrast, anti-LA demonstrated cytoplasmic and mitochondrial staining, and inhibited PDC enzyme activity. Hence, although considerable cross reactivity exists between anti-TFA and anti-LA, the molecular nature of the interaction is clearly different. One of 14 PBC sera reacted weakly with TFA-albumin, whereas four of 14 PBC sera reacted with LA-KLH. Immunohistochemically, both anti-TFA and anti-LA antibodies reacted focally with periportal hepatocytes and bile ducts in both PBC and controls. However, anti-LA produced much stronger focalized staining of the bile ducts of diseased liver. This study suggests that while anti-TFA antibody recognizes lipoic acid-linked enzymes and proteins, the epitope recognized differs from that of anti-LA antibody and PBC autoantibodies. It is unlikely that a response to TFA is the triggering event in PBC. Anti-LA antibodies share a higher degree of similarity to PBC sera providing suggestive evidence that anti-LA antibodies or anti-LA like antibodies (mimotopes) may help define the initiator of the autoimmune response.

Agonist-like activity of antibodies to angiotensin II receptor subtype 1 (AT1) from rats immunized with AT1 receptor peptide

In the present study, rats were immunized with angiotensin II receptor subtype 1 (AT1) receptor peptides for 3 months to see if the immunization produced specific anti-AT1 receptor antibodies and if continuous stimulation for 3 months affected blood pressure or induced morphological changes in the organs containing AT1 receptors. Our results showed that there were constant high levels of circulating antibodies throughout the study period in all rats of the immunized group, but not in the control rats, and that there were almost no significant cross-reactions of antisera with AT2 receptor peptide and alpha1 adrenoceptor peptide, except in four rats, which showed low cross-reactions with alpha1 adrenoceptor and AT2 receptor peptides. When an affinity-purified anti-AT1 receptor antibody was used, it specifically displayed the AT1-stimulatory positive chronotropic effect and also localized AT1 receptors. However, in the immunized group, saturation binding of AT1 in homogenates from kidneys showed no difference either in maximal binding sites (Bmax) or in antagonist affinity (Kd). No difference in mRNA of AT1a was found in either kidney or heart, and no morphological changes in the organs were observed, as compared with the control group. Furthermore, immunization did not cause hypertension. In conclusion, the synthetic peptide corresponding to the second extra-cellular loop of the human AT1 receptor was able to produce highly specific and functionally active anti-AT1 receptor antibodies, but unable to induce pathological structural changes or hypertension.

Testicular hormonal regulation of the renin-angiotensin system in the rat epididymis

Evidence for the existence of an intrinsic angiotensin system based on locally formed angiotensinogen as a precursor for angiotensin production has been demonstrated in the rat epididymis. The data strongly support the presence of an epididymal renin-angiotensin system (RAS) which may be important for epididymal and sperm functions. In the present study, the effects of castration and testicular hormonal replacement on the expression of RAS components from the rat epididymis are investigated at the gene and protein levels. Results from northern blot and western blot analyses consistently showed that the expression of angiotensinogen mRNA and protein was apparently abolished by castration whereas their expression was completely restored to control levels when the castrated rats were hormonally replaced with either testosterone alone or with combined testosterone and estradiol. Northern blot did not detect any signal for angiotensinogen mRNA while western blot could detect a weak signal for angiotensinogen protein when the castrated rats were replaced with estradiol alone. Renin could be detected neither in control, castrated nor hormonally replaced rats. Moreover, the expression of angiotensin II receptor, type I (AT1) was almost abolished by castration as demonstrated by northern blot and reverse transcription-polymerase chain reaction. These data indicate that the expression of RAS by the rat epididymis at the levels of its precursor angiotensinogen and its receptor AT1, is subject to the regulation of testicular hormones and its expression appears to be predominantly testosterone-dependent.

Activation of local renin-angiotensin system by chronic hypoxia in rat pancreas

Previous studies have provided evidence that several key elements of renin-angiotensin system (RAS) are present in the rat pancreas, notably angiotensinogen, which is mandatory for intracellular generation of physiologically active angiotensin II. The data support the existence of an intrinsic RAS, which may be important for pancreatic blood flow and ductal anion secretion. In the present study, the effect of chronic hypoxia on the expression of RAS components, particularly at the levels of its precursor angiotensinogen and its receptor subtypes AT(1) and AT(2), were investigated in the rat pancreas. Results from western blot and semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) analyses unequivocally showed that chronic hypoxia caused a marked increase in angiotensinogen both at the protein and gene levels when compared with that in the normoxic pancreas. However, results from RT-PCR showed that there was a differential effect of chronic hypoxia on the expression of AT(1) and AT(2) receptor subtypes, which exhibited subtype-specific changes in gene expression. For AT(1), chronic hypoxia did not cause a significant change in mRNA expression for AT(1a) but a significant increase in mRNA expression for AT(1b). For AT(2), chronic hypoxia caused a marked increase in its mRNA expression. The increased expression of RAS component genes by chronic hypoxia and its significance of changes may be important for physiological and pathophysiological aspects of the pancreas.

The role of local angiotensins and prostaglandins in the control of anion secretion by the rat epididymis

Secretion of electrolytes and water by the epididymal epithelium is important in the formation of an optimal fluid environment for sperm maturation and storage. Recently, evidence has been obtained that anion/fluid secretion by the epididymis is subject to control by local humoral factors, among which the angiotensins play a significant role. This assertion is based on the morphological localization of various components of a local renin-angiotensin system (RAS) in the rat epididymis and the functional studies of angiotensins and their antagonists on anion secretion in cultured rat epididymal epithelia. More recent study has indicated that the effects of angiotensin II and other vasoactive peptides on anion secretion are mediated through an increase in prostaglandin formation. The pathway of synthesis involves the PLA2-coupled receptor mediated breakdown of membrane phospholipids to arachidonic acid followed by conversion of arachidonic acid into the prostanoids by cyclooxygenases and other enzymes. The newly formed PGE2 then diffuses out of the cells and acts on the EP2/4 receptors on the same or adjacent cells to increase intracellular cAMP. Accordingly, the pathways of activation by the paracrine factors all converge on the cystic fibrosis transmembrane conductance regulator (CFTR) as the final common effector in secretion. Studies on the biochemical pathways of paracrine control of fluid secretion may provide insight into the causes of epididymal irregularities in some forms of male infertility.

Evidence for a locally driven mucosal response and the presence of mitochondrial antigens in saliva in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is often considered to be a dry gland disease caused by frequent involvement of salivary and lacrimal glands. Although high titers of antimitochondrial autoantibodies (AMA) have long been recognized in PBC, little is known about the presence of mitochondrial autoantigens in mucosal compartments such as saliva. We investigated saliva and sera in PBC patients and controls for the presence of AMA and mitochondrial antigens. In PBC saliva, AMA were detected in 45 of 49 (92%), with specificity directed against pyruvate dehydrogenase complex (PDC-E2) alone in 22 of 49 (45%), against PDC-E2 and branched-chain 2-oxo-acid dehydrogenase complex E2 (BCOADC-E2) in 4 of 49 (8%), to PDC-E2 and 2-oxoglutarate dehydrogenase complex E2 (OGDC-E2) in 9 of 49 (18%), and to the 3 antigens together in 10 of 49 (20%). Isotyping of the saliva AMA showed that 80% of the patients had immunoglobulin A (IgA) against PDC-E2, 18% had IgM-specific PDC-E2, and 35% had IgG specific PDC-E2. Similar to serum and bile anti-PDC-E2 IgA antibodies, the saliva autoantibodies localized their reactivity to the inner lipoyl domain of PDC-E2. Furthermore, saliva from patients with PBC but not controls inhibited pyruvate dehydrogenase enzyme activity in vitro. In addition, and of particular interest, we detected a molecule with a molecular weight corresponding to PDC-E2 (74 kd) in PBC but not control saliva. These findings make several important points: first, there appears to be localized mucosal immunity in the secretory system of PBC; second, AMA are readily detected in PBC saliva; and third, PDC-E2 may be present in the saliva of PBC.

Angiotensinogen expression by rat epididymis: evidence for an intrinsic, angiotensin-generating system

Previous studies have suggested the presence of an intrinsic renin-angiotensin system (RAS) in the rat epididymis with functions in epididymal activity and sperm maturation. In the present study, the localization and expression of angiotensinogen, the component of the RAS which is indispensable for intracellular angiotensin generation, were investigated by immunochemistry, hybridization histochemistry and by reverse-transcriptase polymerase chain reaction (RT-PCR). Western blot analysis of protein from the epididymis confirmed the presence of angiotensinogen with the expected molecular mass of about 60 kDa, in agreement with results from other tissues. Immunocytochemistry showed the regional localization of immunoreactivity for angiotensinogen in the rat epididymis. In situ hybridization histochemistry further demonstrated the expression of angiotensinogen mRNA by the epididymal epithelium in a region-specific manner along the length of the rat epididymis. RT-PCR confirmed that the rat epididymis expresses angiotensinogen mRNA. On the other hand, mRNA of renin was not detected in the rat epididymis using Northern blot and RT-PCR analyses. The present study strongly supports the existence of an intrinsic, angiotensin-generating system based on locally formed angiotensinogen as a precursor for angiotensin production. This epididymal RAS may have paracrine or autocrine roles in mediating the epididymal and sperm functions.

Seafood allergy: tropomyosins and beyond

Hypersensitive reactions to seafood is one of the most common food allergies. Despite years of intensive studies, the reasons why some people are allergic to seafood is still unclear. The growing demand for seafood and the subsequent increasing risk of seafood allergy in the population at large make it important to elucidate the molecular basis of seafood allergy and identify the seafood allergens at the molecular level. Here, we discuss the clinical symptoms, physiological mechanisms, current findings of the immunological and molecular basis of shellfish allergy as well as future directions for the prevention of shellfish allergy. Interestingly, identified seafood allergens belong to a group of muscle proteins, namely the parvalbumins in codfish and tropomyosin in crustaceans. In addition, there is strong immunological evidence that tropomyosin is a cross-reactive allergen among crustaceans and mollusks. The molecular cloning, expression and biochemical characterization of seafood allergens will continue to provide valuable tools in the further understanding of the mechanisms of seafood allergy as well as the future development of immunomodulation regimen.

Autoepitope mapping and reactivity of autoantibodies to the dihydrolipoamide dehydrogenase-binding protein (E3BP) and the glycine cleavage proteins in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by the presence of antimitochondrial antibodies (AMA) directed primarily against the E2 subunits of the pyruvate dehydrogenase complex, the branched chain 2-oxo-acid dehydrogenase complex, the 2-oxoglutarate dehydrogenase complex, as well as the dihydrolipoamide dehydrogenase-binding protein (E3BP) of pyruvate dehydrogenase complex. The autoantibody response to each E2 subunit is directed to the lipoic acid binding domain. However, hitherto, the epitope recognized by autoantibodies to E3BP has not been mapped. In this study, we have taken advantage of the recently available full-length human E3BP complementary DNA (cDNA) to map this epitope. In addition, another lipoic binding protein, the H-protein of the glycine cleavage complex, was also studied as a potential autoantigen recognized by AMA. Firstly, the sequence corresponding to the lipoic domain of E3BP (E3BP-LD) was amplified by polymerase chain reaction and recombinant protein and then purified. Immunoreactivity of 45 PBC sera (and 52 control sera) against the purified recombinant E3BP-LD was analyzed by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Secondly, reactivity of PBC sera was similarly analyzed by immunoblotting against H-protein. It is interesting that preabsorption of patient sera with the lipoic acid binding domain of E3BP completely removed all reactivity with the entire protein by immunoblotting analysis, suggesting that autoantibodies to E3BP are directed solely to its lipoic acid binding domain. Fifty-three percent of PBC sera reacted with E3BP-LD, with the majority of the response being of the immunoglobulin G (IgG) isotype (95%). Surprisingly, there was little IgM response to the E3BP-LD suggesting that the immune response was secondary because of determinant spreading. In contrast, H-protein does not appear to possess (or expose) autoepitopes recognized by PBC sera. This observation is consistent with structural data on this moiety.

Localization and distribution of pituitary adenylate cyclase-activating polypeptide in the rat epididymis

Previous investigation has provided evidence for the control of electrogenic chloride secretion by pituitary adenylate cyclase-activating polypeptide (PACAP) across the rat epididymal epithelium using electrophysiological measurement of transepithelial transport in cultured epididymal system. Hence, it suggests that epididymal and sperm functions are subject to control by a local PACAP system in the rat epididymis. In the present study, localization and distribution of PACAP in the rat epididymal duct was studied by an indirect immunofluorescence technique in conjunction with confocal laser scanning microscopy. Immunoreactivity for PACAP was found in all regions of the epididymal duct. However, the intensity of immunoreactivity for PACAP was stronger in the caput and corpus regions when compared to that of the cauda epididymidis. Much weaker immunostaining for PACAP, as compared to those found in other regions, was observed in the cauda epididymal tubules which are in close proximity to the vas deferens. No immunoreactivity for PACAP was found in epididymal spermatozoa. Together with the previous finding, the present results suggest that PACAP may exhibit a regional difference in its expression along the epididymal duct and it may act in a paracrine or autocrine fashion in the regulation of epididymal chloride secretion and hence fluid secretion, thus regulating epididymal and sperm functions along the epididymal duct.

Activation of an adenosine 3',5'-cyclic monophosphate-dependent Cl- conductance in response to neurohormonal stimuli in mouse endometrial epithelial cells: the role of cystic fibrosis transmembrane conductance regulator

Previous studies have demonstrated that Cl- secretion by the mouse endometrial epithelium is under neurohormonal influence. The present study characterized the Cl- conductance activated by a number of agonists in the mouse endometrial epithelial cells using the whole-cell voltage-clamp technique. Adrenaline (1 microM), prostaglandin (PG) E2 (5-10 microM), and PGF2alpha (100 microM) activated a whole-cell current that exhibited a linear I-V relationship as well as time- and voltage-independent characteristics. However, the current magnitude varied with different agonists. The agonist-activated current could be mimicked by an adenylate cyclase activator, forskolin (10 microM), and suppressed by an adenylate cyclase inhibitor, MDL12330A, suggesting the involvement of cAMP. Current characteristics remained the same after cation replacement, leaving Cl- as the major permeant ion species in the solutions. The reversal potential of the agonist-induced current was close to the equilibrium potential of Cl- in the presence of a Cl- gradient, indicating the activation of Cl- conductance. The agonist-induced current was inhibited by the Cl- channel blocker diphenylamine 2,2'-dicarboxylic acid (DPC), but not by the Cl- channel blocker 4,4'-diisothiocyanatostibene-2, 2'-disulfonic acid (DIDS). The anion selectivity sequence of the current was NO3->Br->Cl->I-. The observed electrophysiological properties of the agonist-induced Cl- conductance were consistent with those reported for the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated Cl- channel expressed in many epithelia. The expression of CFTR in the mouse endometrial cells was also demonstrated by Western blot analysis. It appears that neurohormonal regulation of the uterine fluid in the mouse endometrium converges on the cAMP-activated Cl- channel, presumably CFTR.

Regulation of anion secretion by cyclo-oxygenase and prostanoids in cultured epididymal epithelia from the rat

1. The role of cyclo-oxygenase (COX) in the regulation of anion secretion (measured as short- circuit current, Isc) in cultured epididymal epithelia from immature rats was investigated. 2. COX inhibitors attenuated the increase of anion secretion caused by bradykinin (LBK) but had no effect on that caused by PGE2, suggesting that prostaglandin synthesis mediates the secretory response of the tissues to LBK. 3. The apparent IC50 values for indomethacin, piroxicam and L-745,337 in inhibiting the LBK-induced Isc were 0.14, 1.34 and 15.7 microM, respectively. This order of potency: indomethacin > piroxicam > L-745,337 >> DFU suggests the involvement of the COX-1 isozyme in the mediation of the secretory response to LBK. 4. Among the COX products (prostaglandins, thromboxane and prostacyclins) tested, only PGE2 and, to a much lesser extent, PGF2alpha stimulated anion secretion by cultured rat epididymal epithelia. 5. The effect of PGE2 was mimicked by 11-deoxyl PGE1, a specific prostaglandin E (EP)2/4 receptor agonist, but not by sulprostone, a specific EP1/3 receptor agonist, indicating that cyclic AMP-coupled EP2/4 receptors are involved in the LBK-stimulated anion secretion. 6. A reverse transcriptase-polymerase chain reaction study detected the expression of COX-1 and COX-2 mRNA in intact rat epididymis and in cultured epididymal epithelia. The expression of COX-1 mRNA was reduced by LBK by 44 %. 7. Immunohistochemical studies demonstrated the presence of COX-1 immunoreactivity in the basal cells of the intact rat epididymis. By comparison, COX-2 immunoreactivity was detected in the apical pole of the principal cells. 8. The role of COX in the formation of the epididymal microenvironment and the implication of long term administration of non-steroidal anti-inflammatory drugs (NSAIDs) on male fertility are discussed.

Rod-type cyclic nucleotide-gated cation channel is expressed in vascular endothelium and vascular smooth muscle cells

OBJECTIVES

Ca(++)-permeable nonselective cation channels mediate the entry of extracellular Ca++ in vascular endothelium. They are also partly responsible for Ca++ entry in vascular smooth muscle cells (SMCs). The molecular identities of these channels have not been identified. The aim of this study is to examine whether rod-type nucleotide-gated nonselective cation (CNG1) channel, a channel which has been molecularly cloned, is related to the nonselective channels in vascular cells.

METHODS

We used RT-PCR, molecular cloning, northern Blot and in situ hybridization to examine the expression of CNG1 mRNA in a variety of guinea pig and rat blood vessels with different diameters and in cultured vascular endothelial cells and vascular smooth muscle cells.

RESULTS

We have cloned a 402-bp partial cDNA of CNG1 channel from guinea pig mesenteric arteries. RT-PCR and southern blot results indicate that the CNG1 mRNA is expressed in both cultured vascular endothelial and cultured vascular SMCs. Northern blot revealed the transcripts of approximately 3.2 kb, approximately 5.0 kb, and approximately 1.8 kb in cultured endothelial cells. In situ hybridization yielded strong labeling in endothelium layer of aorta, medium-sized mesenteric arteries, and small mesenteric arteries.

CONCLUSION

Our findings suggest a potential role of CNG protein for Ca++ entry in vascular endothelium and vascular smooth muscles. The high expression of CNG1 mRNA in the endothelium of medium-sized arteries and small-sized arteries implicates a possible involvement of CNG1 protein in the regulation of blood supply to different regions and in the regulation of arterial blood pressure.

Expression and localization of the renin-angiotensin system in the rat pancreas

The possibility of an intrinsic renin-angiotensin system (RAS) in the pancreas has been raised by previous studies in which immunohistochemical examination showed the presence of angiotensin II and its receptor subtypes, type 1 (AT1) and type 2 (AT2). In the present study, gene expression of several key RAS components was investigated by reverse-transcription PCR. mRNA expression for angiotensinogen, renin and angiotensin II receptor subtypes, AT1a, AT1b and AT2 was shown. The presence of angiotensinogen protein, the mandatory component for an intrinsic RAS, was demonstrated by Western blotting and localized by immunohistochemistry to the epithelia and endothelia of pancreatic ducts and blood vessels respectively. Immunoblot analysis detected a predominant protein band of about 60 kDa in the pancreas. This was consistent with the predicted value for angiotensinogen as reported in other tissues. Together with previous findings, the present study shows that the rat pancreas expresses the major RAS component genes, notably angiotensinogen and renin, required for intracellular formation of angiotensin II. The data support the notion of an intrinsic RAS in the rat pancreas which may play a role in the regulation of pancreatic functions.

Functional expression of sperm angiotensin II type I receptor in Xenopus oocyte: modulation of a sperm Ca2+-activated K+ channel

In addition to Ca2+ and K+ fluxes, angiotensin II (Ang II) has been shown to influence sperm motility. The present study investigated the involvement of angiotensin II type 1 receptor (AT1) in mediating the modulatory effect of Ang II on a sperm Ca2+-activated K+ channel expressed in Xenopus oocytes injected with RNAs of spermatogenic cells. Ang II at a concentration of 1 microM was found to potentiate the ionomycin-induced current, previously demonstrated to be mediated by a 'Maxi' Ca2+-activated K+ channel. However, at higher concentration, 20 microM, Ang II was found to suppress the ionomycin-induced current. Both potentiating and inhibitory effects of Ang II were blocked by losartan, a specific antagonist of AT1 receptors. Immunohistochemical studies further confirmed the presence of AT1 receptors in spermatogenic cells while expression of AT1 receptor mRNA was demonstrated by RT-PCR. These results suggest that Ang II may influence sperm motility as well as other sperm function by acting on AT1 receptors, and exerting potentiating and inhibitory effects on the Ca2+-activated K+ channels.

Monoclonal antibodies to mitochondrial E2 components define autoepitopes in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by the presence of antimitochondrial Abs (AMA). The autoantigens recognized by AMA are the E2 components of the pyruvate dehydrogenase complex (PDC-E2), the branched chain 2-oxoacid dehydrogenase complex E (BCOADC-E2), and the 2-oxoglutarate dehydrogenase complex E (OGDC-E2). Previous studies using murine monoclonal and human combinatorial Abs to PDC-E2 have demonstrated an intense linear staining pattern in the apical region of biliary epithelial cells (BEC) in PBC but not control liver. We therefore examined whether mAbs to the other mitochondrial autoantigens BCOADC-E2 and OGDC-E2 demonstrated disease-specific patterns of reactivity. Using an expressed recombinant "trihybrid" protein containing the lipoyl domains of PDC-E2, OGDC-E2, and BCOADC-E2, we immunized BALB/c mice to produce 35 mAbs specific for one or more of the above mitochondrial autoantigens. Seven of these mAbs uniquely stained the apical region of BEC in PBC. Of these seven, one was reactive to PDC-E2, two recognized BCOADC-E2, three were reactive to OGDC-E2, and one recognized all three Ags. Our current data demonstrate that, similar to our previous studies regarding PDC-E2, mAbs to BCOADC-E2 and OGDC-E2, or a molecule that cross-reacts with the inner lipoyl domain of all three enzymes, also show a uniquely intense staining pattern in the apical region of BEC in patients with PBC when compared with diseased controls. The abundance of such disease-specific determinants in the target cells of PBC raises interesting possibilities regarding the role of these autoantigens in the pathogenesis of this disease.

Expression of sperm Ca2+-activated K+ channels in Xenopus oocytes and their modulation by extracellular ATP

Ionic fluxes across the sperm membrane have been shown to be important in the initiating process of sperm activation and gamete interaction; however, electrophysiological investigation of the ion channels involved has been precluded by the small size of the sperm, especially in mammalian species. In the present study sperm ion channels were expressed in Xenopus oocytes by injection of RNAs of spermatogenic cells isolated from the rat testes. The RNA-injected oocytes responded to ATP, a factor known to regulate sperm activation, with the activation of an outwardly rectifying whole-cell current which was dependent on K+ concentrations and inhibitable by K+ channel blockers, charybdotoxin (CTX) and tetraethylammonium (TEA). The ATP-induced current could be mimicked by a Ca2+ ionophore but suppressed by a Ca2+ chelator applied intracellularly, indicating a Ca2+ dependence of the current. Single-channel measurements on RNA-injected oocytes revealed channels of large conductance which could be blocked by CTX and TEA. Co-injection of germ cell RNAs with the antisense RNA for a mouse gene encoding slowpoke 'Maxi' Ca2+-activated K+ channels resulted in significant reduction of the ATP- and ionomycin-induced current. The expression of the 'Maxi' Ca2+-activated K+ channels in sperm collected from the rat epididymis was also confirmed by Western blot analysis. These results suggest that sperm possess Ca2+-activated K+ channels which may be involved in the process of sperm activation.

Identification and molecular characterization of Charybdis feriatus tropomyosin, the major crab allergen

BACKGROUND

Crab sensitivity is one of the most common seafood allergies. However, to date, there has been no report on the molecular characterization of crab allergens and no comparative analysis with other seafood allergens.

OBJECTIVE

This study was undertaken to clone, identify, and determine the primary structure of a major IgE-reactive molecule in crab.

METHODS

We constructed an expression cDNA library from a common crab, Charybdis feriatus. This library was then screened with the use of sera from subjects with a well-documented history of type I hypersensitivity reactions upon ingestion of crab. An IgE-reactive clone was chosen and subcloned into plasmids for nucleotide sequence determination and expression in Escherichia coli.

RESULTS

We identified a 1-kb cDNA designated as Cha f 1. Expression of Cha f 1 produces a 34-kd recombinant protein reactive to the IgE antibodies from patients with crab allergies but not from control subjects. Cha f 1 has an opening reading frame of 264 amino acids and demonstrates marked homology to the shrimp tropomyosin Met e 1. Absorption of allergic sera with Cha f I removes IgE reactivity to crab extract. Moreover, absorption of allergic sera with recombinant shrimp Met e 1 tropomyosin removes IgE reactivity to Cha f 1.

CONCLUSIONS

This 34-kd protein, designated as Cha f 1, is the first identified major allergen of crab. Nucleotide and amino acid comparison shows that this protein is the crab tropomyosin. The molecular basis of shrimp and crab allergy is readily demonstrated at the nucleotide and amino acid level.

Induction and persistence of immune-mediated cholangiohepatitis in neonatally thymectomized mice

The availability of recombinant autoantigens allows the experimental study of the relationships between primary biliary cirrhosis (PBC) and mitochondrial antigens. We took advantage of these recombinant autoantigens and attempted to induce autoimmune cholangitis by immunizing neonatally thymectomized (NTx) lipopolysaccharide (LPS)-treated A/J mice, known to be prone to organ-specific autoimmune diseases. We employed a recombinant protein containing a dual-headed molecule that coexpresses the immunodominant epitope of the E2 subunits of the pyruvate dehydrogenase complex and the branched-chain keto-acid dehydrogenase complex. We report herein that an immune-mediated cholangiohepatitis was induced by such immunization and the concurrent injection of LPS into NTx mice. The incidence of cholangitis was 79% in the NTx, immunized, LPS group compared to 14% in the NTx, nonimmunized, LPS group. The histopathology ranged from mild to severe and included bile duct damage, focal hepatic necrosis, and endotheliitis, but no granulomas. Moreover, almost all such lesions persisted for 12 weeks after the discontinuation of immunization and LPS injections in the NTx mice. Interestingly, we were successful (89%) in transferring the cholangiohepatitis by injection of liver infiltrating mononuclear cells from the NTx, immunized, LPS mice into congenic nonimmunized NTx mice; such lesions could not be transferred with spleen cells. Although the pathology is not typical of PBC, this model offers a unique venue for the study of immune-mediated hepatobiliary injury.

Penetration and co-localization in MDCK cell mitochondria of IgA derived from patients with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic autoimmune liver disease of unknown etiology characterized by high-titer anti-mitochondrial antibodies. The major autoantigen has been identified as the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2). The fact that PDC-E2 is present in all nucleated cells, but autoimmune damage is confined to biliary epithelial cells, prompted us to investigate the possibility that mucosally-derived IgA may be pathogenic for biliary epithelial cells. Serum IgA was purified from six patients with PBC and its localization and ability to penetrate cells was studied using Madine-Darby canine kidney (MDCK) cells transfected with the human IgA receptor (MDCK-pIgR). The potential of IgA to be transported through the cells was studied by a combination of immunohistochemistry and dual color fluorescent microscopy. Interestingly, IgA from all PBC patients co-localized with PDC-E2 (the major autoantigen of PBC) inside the cells; this was demonstrated by dual staining with anti-human IgA and a mouse monoclonal antibody directed to PDC-E2. In contrast, no co-localization was observed for IgA controls. Furthermore, dual staining of liver sections from PBC patients demonstrated co-localization of IgA and PDC-E2, both cytoplasmically and at the apical surface. We postulate that there may be a direct effect of these autoantibodies on the mitochondrial function of biliary epithelial cells.

Concurrent and independent HCO3- and Cl- secretion in a human pancreatic duct cell line (CAPAN-1)

The present study investigated both HCO-3 and Cl- secretions in a human pancreatic duct cell line, CAPAN-1, using the short-circuit current (Isc) technique. In Cl-/HCO-3-containing solution, secretin (1 microM) or forskolin (10 microM) stimulated a biphasic rise in the Isc which initially reached a peak level at about 3 min and then decayed to a plateau level after 7 min. Removal of external Cl- abolished the initial transient phase in the forskolin-induced Isc while the plateau remained. In HCO-3/CO2-free solution, on the contrary, only the initial transient increase in Isc was prominent. Summation of the current magnitudes observed in Cl--free and HCO-3-free solutions over a time course of 10 min gave rise to a curve which was similar, both in magnitude and kinetics, to the current observed in Cl-/HCO-3-containing solution. Removal of external Na+ greatly reduced the initial transient rise in the forskolin-induced Isc response, and the plateau level observed under this condition was similar to that obtained in Cl--free solution, suggesting that Cl--dependent Isc was also Na+-dependent. Bumetanide (50 microM), an inhibitor of the Na+-K+-2Cl- cotransporter, and Ba2+ (1 mm), a K+ channel blocker, could reduce the forskolin-induced Isc obtained in Cl-/HCO-3-containing or HCO-3-free solution. However, they were found to be ineffective when external Cl- was removed, indicating the involvement of these mechanisms in Cl- secretion. On the contrary, the HCO-3-dependent (in the absence of external Cl-) forskolin-induced Isc could be significantly reduced by carbonic anhydrase inhibitor, acetazolamide (45 microM). Basolateral application of amiloride (100 microM) inhibited the Isc; however, a specific Na+-H+ exchanger blocker, 5-N-methyl-N-isobutylamiloride (MIA, 5-10 microM) was found to be ineffective, excluding the involvement of the Na+-H+ exchanger. However, an inhibitor of H+-ATPase, N-ethylmaleimide did suppress the Isc (IC50 = 22 microM). Immunohistochemical studies also confirmed the presence of a vacuolar type of H+-ATPase in these cells. H2DIDS (100 microM), an inhibitor of Na+-HCO-3 cotransporter, was without effect. Apical addition of Cl- channel blocker, diphenylamine-2,2'-dicarboxylic acid (DPC, 1 mm), but not disulfonic acids, DIDS (100 microM) or SITS (100 microM), exerted an inhibitory effect on both Cl- and HCO-3-dependent forskolin-induced Isc responses. Histochemical studies showed discrete stainings of carbonic anhydrase in the monolayer of CAPAN-1 cells, suggesting that HCO-3 secretion may be specialized to a certain population of cells. The present results suggest that both HCO-3 and Cl- secretion by the human pancreatic duct cells may occur concurrently and independently.

Molecular and immunological characterization of shellfish allergens

Shellfish (crustaceans and mollusks) have long been known as a common cause of allergic reactions to food. Like other food allergies, the allergic reactions to shellfish involve IgE-mediated Type I hypersensitivity. Biochemical and molecular studies have documented the major shrimp allergen is the muscle protein tropomyosin. Subsequent molecular cloning studies on lobsters and crabs have characterized this protein as the common allergen in crustaceans. There has also been strong immunological evidence that tropomyosin is a cross-reactive allergen among crustaceans and mollusks. This is further confirmed by recent studies on the identification of allergens in squid and abalone. The advances in the characterization of shellfish allergens will not only enhance our understanding on the physiological basis of shellfish allergy but also lay the groundwork for the development of diagnostic and therapeutic design in food allergies.

Characterization of antimitochondrial antibodies in health adults

The detection of antimitochondrial antibodies (AMAs) is an important criterion for the diagnosis of primary biliary cirrhosis (PBC). During the last decade, the mitochondrial autoantigens have been cloned, sequenced, and identified as members of the 2-oxo-acid dehydrogenase pathway, including the E2 subunits of pyruvate dehydrogenase (PDC-E2), branched-chain 2-oxo-acid dehydrogenase (BCOADC-E2), and 2-oxo-glutarate dehydrogenase (OGDC-E2). We have developed a rapid and sensitive diagnostic test for use in PBC based on a triple hybrid recombinant molecule (r-MIT3) that contains the autoepitopes of PDC-E2, BCOADC-E2, and OGDC-E2. To help understand the frequency and antigen specificity of AMAs in an asymptomatic population and to identify patients with early disease, we investigated the prevalence of AMA, by enzyme-linked immunosorbent assay (ELISA), in a cohort of 1,530 people from northern Italy. Positive sera were further analyzed for immunoglobulin (Ig) isotypes, subclasses, and epitopes of AMA by a combination of ELISA and immunoblotting. In this cohort of 1,530 people, 9 (0.5%) reacted to r-MIT3 by ELISA. Of the 9 reactive sera, 2 recognized PDC-E2, 2 of 9 recognized BCOADC-E2, 1 of 9 recognized OGDC-E2, 2 of 9 recognized both PDC-E2 and BCOADC-E2, and 1 of 9 recognized PDC-E2 and OGDC-E2. AMA reactivity was primarily IgM and IgA. Epitope mapping revealed an AMA pattern of reactivity to PDC-E2 that differed from that found in patients with histologically proven PBC in most of the sera. However, 1 sera of a 72-year-old female with a normal alkaline phosphatase had an AMA profile identical to typical PBC. After a variable follow-up period (8-14 months), sera from 8 of 9 of these people were re-obtained for AMA and relative epitope mapping. Interestingly, the reactivity had a wider AMA pattern than before.