[Investigation of the occurrence of musculoskeletal disorders at shoulder, neck and elbow of digestive endoscopy operators].

Objective: To investigate the effect of endoscopic operation volume on musculoskeletal disorders (MSDs) of shoulder, neck and elbow. Methods: From December 2019 to March 2020, random sampling was used to select 200 gastroenterologists from hospitals at or above the municipal level in Sichuan Province as the research object. Gastroenterologists were divided into 108 eadoscop in the low operation group (The operation volume is less than 5 000 cases) and 92 eadoscop in the high operation group (The operation volume is more than 5 000 cases) according to the operation volume. MSDS was investigated by UCLA shoulder scoring system, Tanaka Jingjiu cervical spondylosis scale and improved An and Morrey elbow scoring system, and the chi-square test was used to compare the basic conditions of different body parts in the two groups. The basic condition of each part of the two groups was tested and compared. Results: Compared with the low operation group, the age and working years of the high operation group were longer, and the difference was statistically significant (P<0.001). The most painful part between the two groups was the shoulder, accounting for 25.9% (28/108) and 37.0% (34/92), respectively. Occasional shoulder pain was the most (41.9%, 26/62) and normal function was the most (32.3%, 20/62) ; The forward flexion angle exceeds 150° at most (40.3%, 25/62). Slight pain often occurred in the neck, accounting for 57.7% (15/26), the occasional impact of pain on the upper limbs accounted for 61.5% (16/26), and the impact on the fingers accounted for 53.8% (14/26) ; 65.0% (15/26) had mild disturbance to the sense of signs; Normal tendon reflex accounted for 88.5% (23/26) ; The influence of opponents was weakness, discomfort and no dysfunction, accounting for 53.8% (14/26) ; Endoscopists with normal muscle strength (2 points) and mild decline accounted for 50.0% (13/26) respectively, and there was no significant difference among the groups (P=0.234、1.000、1.000、0.050、0.680、0.539、0.431、0.239). The elbow score scale showed that mild loss accounted for 55.0% (11/20), mild instability accounted for 65% (13/20), and mild pain accounted for 55.0% (11/20) . Conclusion: MSDs is a health problem faced by endoscopists, and targeted preventive measures should be taken for its possible causes.

[Idiopathic pleuroparenehymal fibroelastosis: five case reports and review of literature].

Objective: To raise the awareness of idiopathic pleuroparenehymal fibroelastosis (iPPFE) through investigating the clinical, radiographic and pathological features. Methods: Five cases of iPPFE proved by pathology. The clinical data were studied respectively, and the relevant literature was reviewed. Results: All the cases of iPPFE were manifested by cough and dyspnea. The patients including 3 males and 2 females, aged from 30 to 70 years Chest CT scan showed pleural thickening, subpleural consolidation in both upper lungs complicated with tractive bronchiectasis.Computed tomography-guided percutaneous lung biopsy or surgical lung were performed and the same pathological showed pleura and subpleural dense elastic and collagen fibers. The elastic fibers stain was also positive,which was consistent with PPFE. One patient received low-dose corticosteroid, two received pirfenidone therapy, the others received no treatment. Three patients were stable during the follow-up. Conclusions: iPPFE has characteristic pathological features. However, the number of clinically reported cases is low due to missed diagnosis or misdiagnosed. Improving the understanding of features of iPPFE is helpful for the dianosis, therapy, and prognosis of this disease.

Quercetin and Isoquercitrin Inhibiting Hepatic Gluconeogenesis Through LKB1-AMPKα Pathway.

OBJECTIVE: To observe the impact of quercetin and isoquercitrin on gluconeogenesis in hepatocytes. METHODS: Mouse primary hepatocytes were cultured with lactic acid and pyruvic acid. After treatment with quercetin and isoquercitrin for 24 hours, the glucose concentration in the culture supernatant was determined. RT-PCR was used to detect the mRNAs of PEPCK, G6Pase, LKB1, and AMPKα. Protein levels of LKB1, AMPKα, and Thr172 phosphorylation were evaluated by Western blot. RESULTS: The glucose concentration in the gluconeogenesis group (GN) was significantly higher than in the control group (C), but the glucose concentrations in the high level quercetin(group 80Q) and high level isoquercitrin (group 80I) were significantly lower than in the group GN, P<0.01. In the group 80Q, and group 80I, the mRNA levels of PEPCK and LKB1were significantly lower than in the group GN (P<0.01), and the G6Pase mRNA were significantly lower than in the group GN (P<0.05). The protein levels of LKB1 and the phosphorylation of AMPKα Thr172 in the group 80Q, group 40I, and group 80I were higher than in the group GN. The effects of quercetin and isoquercitrin on LKB1 and AMPKα were similar to those of metformin. CONCLUSIONS: Quercetin and isoquercitrin inhibit gluconeogenesis in hepatocytes, which may be related to the LKB1 upregulation and phosphorylation of AMPKα.

[Epidemiological analysis on a family cluster of COVID-19].

Objective: To understand the possible transmission route of a family cluster of COVID-19 in Zhengzhou and the potential infectivity of COVID-19 in incubation period, and provide scientific evidence for the timely control of infectious source and curb the spread of the epidemic. Methods: Epidemiological investigation was conducted for a family cluster of COVID-19 (8 cases) with descriptive epidemiological method, and respiratory tract samples of the cases were collected for the nucleic acid detection of virus by RT-PCR. Results: Two primary cases, which occurred on 31 January and 1 February, 2020, respectively, had a common exposure history in Wuhan. The other six family members had onsets on 30 January, 31 January, 1 February (three cases) and 3 February, 2020. Conclusions: In this family cluster of COVID-19, six family members were infected through common family exposure to the 2 primary cases. Five secondary cases had onsets earlier than or on the same day as the primary cases, indicating that COVID-19 is contagious in incubation period, and the home isolation in the early phase of the epidemic might lead to the risk of family cluster of COVID-19.

[Application of meticulous anatomy skills with straight bipolar electric coagulation forceps in thyroid surgery].

Objective: To compare the efficacies of the two techniques of "micro-hemostasis and micro-cutting" with straight bipolar electrocoagulation forceps and traditional clamp-ligation for hemostasia in thyroid surgery. Methods: A total of 228 patients who underwent surgical treatment for thyroid neoplasms in our hospital between January 2015 and December 2018 were retrospectively analyzed, including 50 males and 178 females, aged 23-68 years old. Of those, 150 cases as electric knife group received traditional thyroid surgery between January 2015 and December 2018 and 78 cases as bipolar electrocoagulation group received thyroid surgery by using the technique of bipolar electrocoagulation with meticulous anatomy between January 2018 and December 2018. The total operation time, single operation time, intraoperative hemorrhage, postoperative drainage volume on the first day, postoperative hoarseness and hypocalcemia were compared between the two groups. SPSS 16.0 was used to analyze the data. Results: The total operation time and intraoperative hemorrhage in the bipolar electrocoagulation group were significantly lower than those in the electric knife group ((59.33±18.29)min vs (77.21±25.39)min, (14.83±9.22)ml vs (36.86±11.80)ml, all P<0.01). The single operation time of the bipolar electrocoagulation group was shorter than that of the electric knife group((10.25±6.16) min vs (20.34±7.24)min, (16.25±7.15)min vs (35.68±8.25)min, (12.12±5.25)min vs (20.68±7.26)min, t value was 3.948,16.262,8.238, all P<0.01).There was no significant difference between the two groups in postoperative drainage volume on the first day (P>0.05) and the incidence of postoperative hoarseness (P>0.05), while the incidence of hypocalcemia in the bipolar electrocoagulation group(10.26%) was lower than that in the electric knife group(21.33%,χ(2)=4.353, P<0.05). Conclusions: The fine dissection for thyroid operation can be achieved by using straight bipolar electrocoagulation tweezers. The use of "micro-hemostasis" and "micro-cutting" technique with bipolar electrocoagulation tweezers can greatly reduce intraoperative bleeding, operation time and postoperative complication.

Comparative analyses of the complete mitochondrial genomes of Cyathostomum pateratum and Cyathostomum catinatum provide new molecular data for the evolution of Cyathostominae nematodes.

The parasite Cyathostomum pateratum, which occurs in the large intestine of equines, is a common species of the subfamily Cyathostominae. Cyathostominae nematodes are a complex nematode group for which only limited genetic information has been reported. To re-examine the phylogenetic relationships among Cyathostominae nematodes, we sequenced the complete mitochondrial (mt) genome of Cy. pateratum and compared it with the mt genome of the congeneric species Cyathostomum catinatum. The complete mtDNA sequence of Cy. pateratum was 13,822 bp in length, 16 bp shorter than that of Cy. catinatum. The mtDNA sequences of both species contained 12 protein-coding genes, two rRNA genes and 22 tRNA genes, and all 36 genes were transcribed in the same direction and in the same strand. Pairwise comparisons of the 12 predicted amino acid sequences between Cy. catinatum and Cy. pateratum revealed differences of 0.4-3.1%; the least conserved sequence was that of cytochrome c oxidase subunit 3 (cox3). Phylogenetic analysis of the concatenated amino acid sequences using Bayesian inference and maximum likelihood methods showed that Cy. catinatum and Cy. pateratum clustered together with very high nodal support, and Cylicostephanus goldi was closer to the Cyathostomum nematodes than to other Cyathostominae nematodes. The mtDNA sequence of Cy. pateratum is reported here for the first time. The study will shed some light on the genetic evolution among parasitic nematodes in Cyathostomum.

Molecular mechanism of Wnt signal pathway in multiple myeloma cell line H929 cell autophagy.

OBJECTIVE: Pathogenic mechanism of multiple myeloma is still unclear yet. Abnormality in cell autophagy is closely correlated with various orthopedic diseases especially multiple myeloma. Therefore, this study investigated the mechanism of cell autophagy abnormality in multiple myeloma occurrence and clinical implications. MATERIALS AND METHODS: Using multiple myeloma cell line H929 as the model, cells were treated with UV irradiation. Western blot was used to measure the autophagy of H929 cell, expression level of autophagy molecules and activation of autophagy signal pathway such as Wnt. Using autophagy activator, H929 cell autophagy was potentiated, followed by quantification of autophagy molecular expression and signal pathway such as Wnt activation. Agonist or antagonist of Wnt signal pathway was used to treat H929 cells followed by measuring autophagy molecules and Wnt pathway activation. The correlation between Wnt signal pathway or cell autophagy and occurrence of multiple myeloma was analyzed. RESULTS: UV irradiation treatment on multiple myeloma cell line H929 induced autophagy and Wnt signal pathway activation. The inhibitor of Wnt signal pathway suppressed UV-induced H929 cell autophagy. However, over-expression of Wnt signal pathway enhanced UV-mediated autophagy of H929 cells. The condition of Wnt activation and autophagy level were positively correlated. CONCLUSIONS: UV irradiation can induce autophagy of multiple myeloma cells, suggesting that management of cell autophagy might be one possible treatment for multiple myeloma.

Hypoxia-induced apoptosis and mitochondrial dysfunction in chondrocytes arising from CREB phosphorylation reduction.

Chondrocytes, which are embedded within the growth-plate or the intervertebral disc, are sensitive to environmental stresses, such as inflammation and hypoxia. However, little is known about the molecular signaling pathways underlying hypoxia-induced mitochondrial dysfunction and apoptosis in chondrocytes. We first examined the apoptosis, caspase-3 activity, and apoptosis-associated markers in human chondrocyte cell line C28/I2 under normoxia or hypoxia. We then investigated mitochondrial dysfunction and the activation of cyclic adenosine monophosphate response element-binding protein (CREB) signaling in the same human chondrocyte cell line. Our results indicated that hypoxia induced apoptosis and reduced CREB phosphorylation in chondrocytes. Upregulated mitochondrial superoxide and reactive oxygen species levels, and reduced mitochondrial membrane potential and complex IV activity were observed in hypoxia-treated C28/I2 cells. In conclusion, the present study confirmed reduced CREB phosphorylation, apoptosis induction, and mitochondrial dysfunction in the hypoxia-treated chondrocyte cells. This implies the key role played by CREB signaling in hypoxia-induced mitochondrial dysfunction and apoptosis in chondrocytes.

The identification of the biological characteristics of human ovarian cancer stem cells.

OBJECTIVE: Identifying the biological characteristics of previously screened ovarian cancer cell line HO8910-derived stem cells. MATERIALS AND METHODS: The pre-screening of ovarian cancer cell line HO8910-derived stem cells were subcultured (HO8910 cells were used as a control group) in serum-free medium. Firstly, the capacities of forming spheroids and self-renewal were observed. Then ovarian cancer stem cells (CSCs) were seeded in medium containing serum and cultured to observe the changes in their ability to differentiate. The stem cell-specific markers were also tested. Secondly, we tested the sensitivity of stem cells to cisplatin, doxorubicin, and mitoxantrone using drug susceptibility test. Finally, we inoculated the ovarian CSCs after passaging from culturing in serum-free media to NOD/SCID (non-obese diabetic/severe combined immunodeficient mice) mice in order to observe the tumorigenicity in vivo. RESULTS: Ovarian CSCs cultured in serum-free medium are capable of forming stable passaged cells spheres and have strong ability of self-renewal and differentiation. Under the condition of serum-free medium culture, the expression levels of CDl33+, CD117+, ABCG2, Nanog, Oct4, and BCRP in ovarian cancer stem cell are significantly higher than the counterparts in HO8910 cells. With the increase of the ability of differentiation, the stem cell marker expression levels reduced. While the differentiation, potential marker-E-cadherin expression levels were significantly lower than the control group. With the increase of the ability to differentiate, E-cadherin expression level was increased. Ovarian CSCs have significant resistance to cisplatin, doxorubicin, and mitoxantrone. NOD/SCID nude mice experiments showed that ovarian cancer stem cell tumorigenicity was significantly higher than control cells and has a continuous tumorigenicity. CONCLUSIONS: Comparing ovarian CSCs derived from HO8910 to HO8910 cells, the stem cells have significantly enhanced abilities of self-renewal, differentiation, in vivo tumorigenicity, highly expressed stem cell genes, and multidrug resistance.

Impact of basiliximab on the proportion of regulatory T cells and their subsets early after renal transplantation: a preliminary report.

OBJECT: This study aims to investigate the impact of anti-CD25 monoclonal antibody (basiliximab) on peripheral blood regulatory T cells (Treg) and their subsets in recipients early after renal transplantation. METHODS: Ten renal transplant recipients from November 2009 to February 2011 were divided into an induction therapy and a no-induction therapy group, mainly based on their will to accept basiliximab induction. Peripheral blood samples were collected at 2 hours before as well as 1 and 2 weeks after transplantation. Flow cytometry was used to analyze the proportion of regulatory T cells and their subsets. RESULTS: Compared with the no-induction therapy group, the proportions of both CD25(high) T cell and CD25(high) Foxp3(+) double marked T cells were significantly decreased among in the basiliximab induction group remaining at low at 2 weeks. The subsets of activated Treg and cytokine-secreting Treg were also temporarily downregulated at 1 week after transplantation using basiliximab induction. However, the inhibitory transcriptional factor Foxp3 was not significantly affected by the induction therapy. CONCLUSIONS: Anti-CD25 monoclonal antibody downregulated the proportion of regulatory T cell and its activated subsets in peripheral blood in the early stage after renal transplantation while the inhibitory function may still be spared.

Regulation of the renal Na-HCO(3) cotransporter. XI. Signal transduction underlying CO(2) stimulation.

We have previously shown that CO(2) stimulation of the renal Na-HCO(3) cotransporter (NBC) activity is abrogated by general inhibitors of protein tyrosine kinases. The more selective inhibitor herbimycin also blocked this effect at concentrations known to preferentially inhibit Src family kinases (SFKs). We therefore examined a role for SFKs in CO(2)-stimulated NBC activity. To this end, we engineered OK cells to express the COOH-terminal Src kinase (Csk), a negative regulator of SFKs. CO(2) stimulated NBC activity normally in beta-galactosidase-expressing and untransfected control cells. In contrast, Csk-expressing cells had normal baseline NBC activity that was not stimulated by CO(2). CO(2) stimulation increased both total SFK activity and specific tyrosine phosphorylation of Src. The specific MEK1/2 inhibitor PD-98059 completely inhibited the CO(2) stimulation of NBC activity as well as the accompanying phosphorylation and activation of ERK1/2. Our data suggest the involvement of both SFKs, probably Src, and the "classic" MAPK pathway in mediating CO(2)-stimulated NBC activity in renal epithelial cells.

Regulation of the renal Na-HCO(3) cotransporter X. Role of nitric oxide and intracellular calcium.

Cholinergic agents increase the activity of the renal Na-HCO(3) cotransporter and have been shown to stimulate the production of nitric oxide (NO) in other cells. To study the role of NO in mediating the effect of carbachol on Na-HCO(3) cotransporter, we measured the activity of the cotransporter in rabbit proximal tubule cells treated with carbachol (10(-4 )M) or the NO inhibitor, L-NAME (10(-3) M), or carbachol+L-NAME. The activity of NaHCO(3) cotransporter was measured by recovery of intracellular pH (pH(i)) in cells loaded with pH-sensitive dye, BCECF. In control cells, carbachol significantly increased Na-HCO(3) cotransporter activity while L-NAME did not affect the activity of the cotransporter but completely blocked the enhancement induced by carbachol. Carbachol increased NO production by proximal tubule cells. We also studied the effect of the NO donor, SNAP (10(-3) M), on the cotransporter incubated for 1 h in cultured proximal tubule cells. SNAP caused a similar enhancement in the activity of the cotransporter suggesting that a different NO donor is capable of enhancing the activity of the cotransporter to the same extent as that observed with carbachol. Because the effect of NO is thought to involve cGMP, we examined the effect of 8-Br-cGMP (10(-3 )M) on the cotransporter. 8-Br-cGMP caused stimulation of the Na-HCO(3) cotransporter activity although to a lesser degree than carbachol. We have previously shown that carbachol increases cytosolic calcium but the role of intracellular calcium (Ca(i)) per se on the cotransporter has not been studied. We therefore studied the role of Ca(i) on the activity of Na-HCO(3) cotransporter in rabbit proximal tubule cells by utilizing the calcium ionophore, ionomycin, the microsomal Ca-ATPase inhibitor, thapsigargin, and the calcium chelator, BAPTA. Ionomycin, 5 microM, caused a significant stimulation of Na-HCO(3) cotransporter which was prevented by BAPTA. The microsomal Ca-ATPase inhibitor, thapsigargin, also increased the cotransporter activity. As expected both ionomycin and thapsigargin caused a significant increase in Ca(i). Calyculin A, an inhibitor of protein phosphatase 2A prevented the stimulation of the cotransporter by calcium (in pH units/min: control 1.8+/-0.13; Ca 2.22+/-0.07; p<0.05; Ca+calyculin A 1.9+/-0.09, p<0.025) suggesting that calcium acting through kinases/phosphatases, plays a role in the phosphorylation of the cotransporter. These results demonstrate that NO and Ca(i) modulate the activity of the cotransporter.

Regulation of the renal Na-HCO3 cotransporter: IX. Modulation by insulin, epidermal growth factor and carbachol.

To examine the role of tyrosine kinase (TK) on basolateral membrane (BLM) transport, we looked for the presence of TK activity in these membranes and showed that the synthetic substrate for TK, poly [Glu80 Na, Tyr20] caused a three-fold increase in tyrosine phosphorylation. This effect was completely blocked by the TK inhibitors, 2-hydroxy-5(2,5-dihydroxybenzyl) aminobenzoic acid (HAC), 1 microM, and methyl 2,5-dihydroxycinnamate (DHC), 5 microM. We then examined the effect of agents that cause TK stimulation on tyrosine kinase immunocontent and on the Na-HCO3 cotransporter activity in BLM and in primary cultures of the proximal tubule. We utilized the cholinergic agent, carbachol (10(-4) M), epidermal growth factor (EGF 10(-8) M), and insulin (10(-8) M), well known activators of TK. Carbachol, insulin, and EGF caused a significant increase in TK immunoreactive protein content which was blocked by HAC and DHC. In BLM, carbachol significantly stimulated HCO3-dependent 22Na uptake and this effect was totally prevented by the monoclonal antibody against TK. In cultured proximal tubule cells, carbachol, EGF and insulin at physiologic concentration caused a significant stimulation of the cotransporter activity and this effect was completely blocked by the TK inhibitor, HAC. Increasing the dose of insulin 100-fold did not cause further stimulation of the cotransporter indicating that insulin plays a permissive role on the cotransporter. These results demonstrate the presence of TK in renal proximal tubule cells and show that activation of this kinase by dissimilar agents enhance the activity of the Na-HCO3 cotransporter.

Regulation of renal Na-HCO3 cotransporter: VIII. Mechanism Of stimulatory effect of respiratory acidosis.

We examined the effect of respiratory acidosis on the Na-HCO3 cotransporter activity in primary cultures of the proximal tubule of the rabbit exposed to 10% CO2 for 5 min, 2, 4, 24 and 48 hr. Cells exposed to 10% CO2 showed a significant increase in Na-HCO3 cotransporter activity (expressed as % of control levels, 5 min: 142 +/- 6, 2 hr: 144 +/- 13, 4 hr: 145 +/- 11, 24 hr: 150 +/- 15, 48 hr: 162 +/- 24). The increase in activity was reversible after 48 hr. The role of protein kinase C (PKC) on the stimulatory effect of respiratory acidosis on the cotransporter was examined in presence of PKC inhibitor calphostin C or in presence of PKC depletion. Both calphostin C and PKC depletion prevented the effect of 10% CO2 for 5 min or 4 hr to increase the activity of the cotransporter. 10% CO2 for 5 min or 4 hr increased total and particulate fraction PKC activity. To examine the role of phosphotyrosine kinase (PTK) on the increase in cotransporter activity we studied the effect of two different inhibitors, 2-hydroxy-5-(2,5-dihydroxylbenzyl) aminobenzoic acid (HAC) and methyl 2,5-dihydroxycinnamate (DHC) which inhibit phosphotyrosine kinase in basolateral membranes. Cells were pretreated either with vehicle or HAC or DHC and then exposed to 10% CO2 for 5 min or 4 hr. In cells treated with vehicle, 10% CO2 significantly increased cotransporter activity as compared to control cells exposed to 5% CO2. This stimulation by 10% CO2 was completely prevented by HAC or DHC at 5 min (5% CO2: 1.8 +/- 0.2, 10% CO2: 2.6 +/- 0.2, 10% CO2 + HAC: 1.6 +/- 0.2, 10% CO2: +DHC: 2.0 +/- 0.3 pH unit/min) and also at 4 hr. The protein synthesis inhibitors actinomycin D and cycloheximide appear to prevent the effect of 10% CO2 for 4 hr on the cotransporter. Our results show that early respiratory acidosis stimulates the Na-HCO3 cotransporter through PKC and PTK-dependent mechanisms and the late effect appears to be mediated through protein synthesis.

Regulation of the renal Na-HCO3 cotransporter: VII. Mechanism of the cholinergic stimulation.

Cholinergic agents regulate proximal tubule acidification but the mechanism responsible for this effect is unclear. We examined the effect of the cholinergic agent carbachol on the activity of the Na-HCO3 cotransporter in primary cultures of the proximal tubule of the rabbit. The activity of the cotransporter was assayed either as HCO3-dependent 22Na uptake or as the recovery of intracellular pH in cells perfused continuously with Cl-free physiologic solution containing amiloride to block the Na-H antiporter. Carbachol caused a dose-dependent stimulation of the cotransporter activity with a maximum increase of 90% above control values at 10(-5) M and half maximal stimulation at 10(-7) M. The stimulation was blocked by atropine and pirenzepine indicating an effect through the M1 muscarinic receptor. Carbachol increased intracellular calcium fourfold and the rise in cytosolic calcium was prevented by the intracellular calcium chelator, BAPTA. BAPTA also blocked the effect of carbachol on the cotransporter. Because carbachol activates phospholipase C and protein kinase C, we examined the effect of carbachol in the presence of the phospholipase C inhibitor, U73122, or the PKC inhibitor, calphostin C, or PKC depletion. The phospholipase C inhibitor prevented both the effect of carbachol on the cotransporter and on the intracellular Ca. Calphostin C and PKC depletion also prevented the stimulation of the cotransporter. Carbachol increased PKC activity and caused translocation of the PKC to the particulate fraction. We also examined the effect of the phosphatase inhibitor, calyculin A or the calmodulin kinase inhibitor, W-13 on carbachol stimulation. Calyculin A and W13 likewise prevented the carbachol-induced stimulation of the cotransporter. These results demonstrate that cholinergic stimulation modulated the activity of the cotransporter through multiple pathways including phospholipase C/PKC and phosphatase systems.

Inhibition of phosphatidylinositol-3'-kinase prevents induction of endotoxin tolerance in vitro.

Previous studies have shown an increase in the expression of phosphatidylinositol-3'-kinase (PI-3'-K) in macrophages from endotoxin tolerant (ET) rats. This implicates PI-3'-K cell signaling in attenuated macrophage responsiveness to lipopolysaccharide (LPS). These experiments examined the effects of selective pharmacologic inhibition of PI-3'-K in an in vitro model of ET. To induce ET, RAW 264.7 macrophages cultured in RPMI 1640 with 10% fetal calf serum were initially exposed to 10 ng/ml LPS (E. coli 0111:B4) for 19 hr. Non-tolerant cells received an equal volume of phosphate buffered saline. Some cultures were also incubated with the specific PI-3'-K inhibitor wortmannin (10 nM) during this tolerizing period. Cells were then washed and re-challenged with 100 ng/ml LPS for 24 hr. Next, macrophage tumor necrosis factor-alpha (TNF-alpha) and nitrite production were measured as indicators of ET induction. Macrophage TNF-alpha production decreased significantly while nitrite production increased significantly following ET induction. Specific inhibition of PI-3'-K prevented this decrease in TNF-alpha and increase in nitrite production in ET macrophages. Production of each mediator returned to levels not different than in non-tolerant macrophages. In this in vitro model of macrophage ET, pharmacologic inhibition of the PI-3'-K signaling pathway prevented the induction of LPS tolerance as measured by the production of two inflammatory mediators.

Regulation of the renal Na-HCO3 cotransporter: VI. Mechanism of the stimulatory effect of protein kinase C.

We have previously shown that the activity of the Na-HCO3 cotransporter is stimulated by protein kinase C (PKC) activation, but the mechanism responsible for this effect is not clear. We have shown that cultured proximal tubule cells of the rabbit have DIDS-sensitive Na-HCO3 cotransporter activity as assessed by HCO3-dependent 22Na uptake or by measurement of intracellular pH. In cells loaded with BCECF and treated with the amiloride analogue, ethylisopropyl amiloride, removal of extracellular Na was associated with a rapid decrease in pH which returned to normal with re-addition of Na. This pH recovery was inhibited by DIDS and was used to quantify the activity of the Na-HCO3 cotransporter. In the present study, we utilized primary cultures of the proximal tubule of the rabbit to examine the effect of PKC activation on the activity of the Na-HCO3 cotransporter. Short term incubation (5 min) with the active phorbol ester, phorbol 12-myristate, 13-acetate (PMA), 10(-7) M, caused a significant stimulation of the Na-HCO3 cotransporter activity as compared to controls. Incubation for two hours also caused a significant stimulation of the Na-HCO3 cotransporter activity. The inactive analogue of PMA, 4-alpha phorbol, failed to alter the cotransporter. Similar results were observed when we examined the effect of PMA on HCO3-dependent 22Na uptake. The effect of PMA to stimulate the cotransporter was mediated by PKC activation since it could be prevented by the PKC inhibitors, calphostin C or sphingosine, or by prior PKC depletion. The long term but not the short term effect of PMA to stimulate the Na-HCO3 cotransporter activity was prevented by the protein synthesis inhibitors, actinomycin D or cycloheximide. The early effect of PKC to stimulate the cotransporter appeared to be associated with increased phosphorylation of a 56 kD protein band, while the late effect appeared to be associated with an increase in immunoreactive content of a 56 kD protein which is thought to be an active component of the cotransporter. Thus PKC stimulation activates the Na-HCO3 cotransporter by two distinct mechanisms: a long term effect which is protein synthesis-dependent and a short term effect which is protein synthesis-independent and is likely mediated by phosphorylation.

Regulation of the renal Na-HCO3 cotransporter: V. mechanism of the inhibitory effect of parathyroid hormone.

PTH administration decreases proximal HCO3 reabsorption and inhibits the brush border Na-H antiporter. We studied the effect of PTH on the renal Na-HCO3 cotransporter and examined whether this effect is mediated through the adenylate cyclase/cyclic AMP system or through the phospholipase A pathway. We studied the effect of PTH [1-34] on the Na-HCO3 cotransporter activity in rabbit renal basolateral membranes incubated with 50 microM ATP by measuring the 22Na uptake in the presence of HCO3 and gluconate. Na-HCO3 cotransporter activity (expressed in nmol/mg protein/3 seconds) was taken as the difference in 22Na uptake in the presence of HCO3 and gluconate. PTH (10(-10) M) completely inhibited Na-HCO3 cotransporter activity from 1.23 +/- 0.14 to -0.58 +/- 0.23, P < 0.001. This effect of PTH to inhibit the Na-HCO3 cotransporter was prevented by the polyclonal antibody against G alpha s indicating that PTH acts through G alpha s protein. Because G alpha s stimulates adenylate cyclase/cyclic AMP system, we examined the effect of PTH in the presence and in the absence of the adenylate cyclase inhibitor, dideoxyadenosine (DDA). DDA alone (10(-4) M) stimulated the Na-HCO3 cotransporter activity. In the presence of DDA, the net inhibitory effect of PTH was the same magnitude as that of control, suggesting the existence of other pathways for the effect of PTH on the cotransporter. Calmodulin inhibition also partially prevented the effect of PTH. To determine whether the inhibitory effect of PTH is mediated at least in part, through phospholipase A, we first examined the effect of PTH on arachidonic acid release and then measured the Na-HCO3 cotransporter activity in presence and in absence of arachidonic acid or eicosatetraynoic acid (ETA), an inhibitor of arachidonic acid metabolism. PTH significantly increased the release of arachidonic acid by isolated proximal tubule cells and arachidonic acid inhibited the Na-HCO3 cotransporter in basolateral membranes. ETA (3 microM) partially prevented the inhibitory effect of PTH. In cultured proximal tubule cells, PTH inhibited the HCO3-dependent 22Na uptake and ethoxyresorufin, an inhibitor of cytochrome P-450, blocked the inhibitory effect of PTH on the cotransporter. These results demonstrate that PTH inhibits the renal Na-HCO3 cotransporter through multiple mechanisms, that are mediated through G proteins, G alpha s and GP, and CaM-KII.

The renal cortical Na-HCO3 cotransporter: V. expression in Xenopus oocytes.

The Na-HCO3 cotransporter is the main system responsible for HCO3 transport from proximal tubule cells into the blood. the expression of the renal cortical basolateral Na-HCO3 cotransporter was studied in Xenopus laevis oocytes. Injection of mRNA prepared from renal cortex into oocytes enhanced HCO3-dependent 22Na uptake on average 6-fold, (range:2-44) compared with vehicle-injected oocytes, without altering 22Na uptake in presence of gluconate. These findings indicate that mRNA selectively expresses Na-HCO3 cotransporter activity without altering diffusive 22Na uptake. The expressed Na-HCO3 cotransporter activity had a Km for Na of 20 mM, was electrogenic and sensitive to disulfonic stilbenes. In presence of HCO3, the expressed Na-HCO3 cotransporter activity was like the native cotransporter, enhanced by carbonate or sulfite, a finding compatible with the existence of distinct sites for HCO3 and carbonate on the transport system. After fractionation by a sucrose density gradient, the mRNA fraction responsible for the Na-HCO3 cotransporter was found to be between 1.50 and 3.48 kb classes.

Regulation of the renal Na-HCO3 cotransporter: IV. Mechanisms of the stimulatory effect of angiotensin II.

Angiotensin II stimulates proximal tubule acidification by activating both the Na-H antiporter and the Na-HCO3 cotransporter. The mechanism whereby angiotensin II stimulates the Na-HCO3 cotransporter was investigated in renal cortical basolateral membrane vesicles of the rabbit by measuring 22Na uptake in the presence of HCO3 and gluconate. Na-HCO3 cotransporter activity (expressed in nanomoles per milligram of protein per 3 s) was taken as the difference in 22Na uptake in the presence of HCO3 and gluconate. Angiotensin II stimulated Na-HCO3 cotransporter activity significantly (control, 1.5 +/- 0.4; angiotensin II, 3.3 +/- 0.6; P < 0.05), and this stimulation was prevented by the angiotensin II receptor antagonist DuP 753. Angiotensin II has been shown to stimulate both pertussis toxin-sensitive Gi protein and pertussis toxin-insensitive Gq protein. In the presence of pertussis toxin, angiotensin II (10(-11) M) failed to stimulate the Na-HCO3 cotransporter, suggesting a role of Gi protein in mediating this effect. In the presence of a polyclonal antibody against Gi protein, angiotensin II failed to stimulate the Na-HCO3 cotransporter (control, 1.6 +/- 0.4; angiotensin II, 3.9 +/- 0.9; angiotensin II + Gi, 1.2 +/- 0.7). Angiotensin II stimulated inositol triphosphate release, and this effect could be blocked by the phospholipase C inhibitor U73122, suggesting a role of phospholipase C or A2 in this effect of angiotensin II. In the presence of the protein kinase C inhibitor calphostin C (50 nM), angiotensin II also failed to stimulate the Na-HCO3 cotransporter. These results demonstrate that angiotensin II stimulates the renal Na-HCO3 cotransporter by interacting with a specific angiotensin II receptor and that this stimulation is mediated by the activation of Gi and Gq proteins.