An experimental study of endovascular stenting with special reference to the effects on the aortic vasa vasorum

PURPOSE

To evaluate the effects of bare stents and covered stents on the aortic wall, especially the vasa vasorum.

METHODS

Eight bare stents and nine covered stents were placed in the infrarenal aorta of nine dogs. The dogs were euthanized at 4-45 weeks after stent placement. The vasa vasorum was evaluated by microstereoscopy with vascular casting, and the histopathology of the aortic wall was examined by light microscopy.

RESULTS

In the unstented normal aorta, vasa vasorum nourished the adventitia and the outer media, and the intima and inner media were avascular. In the stented segment, vascular dilatation and proliferation of vasa vasorum, medial atrophy, and intimal hyperplasia were observed, more prominent for covered stents than for bare stents.

CONCLUSION

Intravascular stent placement caused not only medial atrophy and intimal hyperplasia but also proliferation of the vasa vasorum, probably due to hypoxia in the aortic wall.

[The relationship of carcinoembryonic antigen and neutrophils to pulmonary function in healthy smokers]

We evaluated the relationship of carcinoembryonic antigen (CEA) and neutrophils to pulmonary function in healthy smokers. Smokers in whom levels of CEA were greater than 5.0 ng/ml (n = 70) and in whom CEA levels were 5.0 ng/ml or less (n = 693) had significantly higher mean concentrations of leukocytes and neutrophils than non-smokers (n = 651) (leukocytes: 6,883 +/- 1,889/mm3 or 5,581 +/- 1,457/mm3 vs. 4,507 +/- 1,111/mm3, p < 0.01; neutrophils: 4,389 +/- 1,542/mm3 or 3,343 +/- 1,164/mm3 vs. 2,700 +/- 884/mm3, p < 0.01). Differences in the ratio of vital capacity to the predicted vital capacity (%VC) were not significant. In addition, the ratio of forced expiratory volume in one second to forced vital capacity (FEV 1.0%) in smokers with CEA levels greater than 5.0 ng/ml was decreased compared with smokers with CEA levels of 5.0 ng/ml or less and in non-smokers (90.2 +/- 8.4% vs. 93.3 +/- 6.7% or 92.9 +/- 6.5%, p < 0.01). These results suggest that in healthy smokers high serum CEA levels are related to a decreased FEV 1.0%.

Nefiracetam modulates acetylcholine receptor currents via two different signal transduction pathways

Nootropic agents are proposed to serve as cognition enhancers. The underlying mechanism, however, is largely unknown. The present study was conducted to assess the intracellular signal transduction pathways mediated by the nootropic nefiracetam in the native and mutant Torpedo californica nicotinic acetylcholine (ACh) receptors expressed in Xenopus laevis oocytes. Nefiracetam induced a short-term depression of ACh-evoked currents at submicromolar concentrations (0.01-0.1 microM) and a long-term enhancement of the currents at micromolar concentrations (1-10 microM). The depression was caused by activation of pertussis toxin-sensitive, G protein-regulated, cAMP-dependent protein kinase (PKA) with subsequent phosphorylation of the ACh receptors; in contrast, the enhancement was caused by activation of Ca(2+)-dependent protein kinase C (PKC) and the ensuing PKC phosphorylation of the receptors. Therefore, nefiracetam interacts with PKA and PKC pathways, which may explain a cellular mechanism for the action of cognition-enhancing agents.

Identification of Dermatophagoides farinae-2-derived peptides and class II HLA molecules recognized by T cells from atopic individuals

Der f2, the group 2 allergen of Dermatophagoides farinae, is one of the major inhalation allergens in Japan. Using the mixture of a panel of overlapping synthetic peptides that spread over the entire Der f2 molecule, we found that polyclonal Der f2-specific short-term T cell lines prepared from peripheral blood mononuclear cells of 5 individuals allergic to Der f who carry most of the common HLA haplotypes seen in the Japanese population can respond mainly to 7 different peptides. Distribution of the T cell epitopes on Der f2 was not identical with that on Der p2. Five of 7 peptides stimulated T cells of more than 2 donors, regardless of HLA types. Inhibition patterns by anti-HLA class II mAbs were heterogenous in proliferative responses of each cell line, three were mainly inhibited by anti-HLA-DR mAb, and the others were inhibited by anti-HLA-DQ mAb. One of these T cell lines, SM, of which the proliferative response was partially inhibited by anti-HLA-DQ mAb, was cloned. Indeed, the T cell clone SM4.6 was restricted by DQ6 molecules encoded for by an HLA-DRB1*1502-DRB5*0102-DQA1*0103-DQB1*0601 haplotype. These results indicate that patients' T cells recognize Der f2 in association with a variety of HLA-DR or HLA-DQ as antigen-presenting molecules. Thus, although some peptides do have a more potent T cell stimulatory activity than others, the TCR ligands formed with the Der f2 molecule are highly heterogeneous, a factor also noted in Der f1-specific T cell lines in our previous study.

Early-onset facioscapulohumeral muscular dystrophy: two case reports

This report concerns two patients with facioscapulohumeral muscular dystrophy (FSHD) whose facial weakness began in infancy. In both patients, biopsied muscle histology showed mild myogenic changes accompanied by some regenerating and some small angular fibers, while endomysial inflammatory cellular infiltration was observed in Patient 1. The finding that our very young patients had muscle histopathological findings compatible with classical FSHD supports the previously expressed view that muscle histopathology is not related to either age or duration of the disease. Although Patient 2 was a sporadic case, both patients had the abnormal EcoRI DNA fragment detected by Southern blot analysis with probes p13E-11 and pFR-1, a finding compatible with FSHD. This indicates that gene analysis of sporadic cases must be as significant as that of familial cases. This report on patients with very early-onset and with common muscle histopathological and molecular genetic findings should contribute to widening the clinical spectrum of FSHD.

The voltage-dependent non-selective cation channel sensitive to the L-type calcium channel blocker efonidipine regulates Ca2+ influx in brain vascular smooth muscle cells

The present study investigated the ion channel responsible Ca2+ influx in cultured smooth muscle cells from bovine brain arteries by monitoring Ba2+ currents. Voltage pulses at a range between -100 and +100 mV from a holding potential of 0 mV induced currents and the current/voltage (I/V) relations were linear with a reversal potential of +/- 0 mV. The currents were increased by elevating extracellular Ba2+ concentrations, suggesting that the voltage-sensitive non-selective cation channel, which favors Ca2+ influx, is expressed in brain vascular smooth muscle cells. In contrast, when voltage pulses at a range between -50 to +50 mV from a holding potential of -80 mV were applied to carotid smooth muscle cells, inward currents were evoked by depolarization to > or = -10 mV and the I/V relations were bell-shaped, typical for the L-type calcium channels. The dihydropyridine derivatives, efonidipine and nicardipine, inhibited the L-type Ca2+ channel-operated currents in carotid smooth muscles, and further efonidipine had an inhibitory effect also on non-selective cation currents in brain vascular smooth muscle cells. These results suggest that the voltage-dependent non-selective cation channel expressed in brain vascular smooth muscle cells is sensitive to a kind of the dihydropyridine derivatives and regulates Ca2+ influx.

Determination of methemoglobin and carboxyhemoglobin in blood by rapid colorimetry

A sensitive and rapid colorimetry for determination of methemoglobin (MetHb) in hemolysate of the test blood was devised by measurement of absorbance at 563 nm, the isosbestic point of spectra of cyanomethemoglobin and oxyhemoglobin, at pH 6.8. MetHb was determined as the difference in absorption caused by cyanide in the absence of potassium ferricyanide divided by the difference in absorption caused by cyanide in the presence of the ferricyanide. Carboxyhemoglobin (COHb) in the blood was also estimated from the absorbance values of the hemolysates with or without potassium ferricyanide after the addition of cyanide. The method requires only 3 microliters of test blood and 10 min for determinations of MetHb and COHb in blood. Results obtained by the method were in satisfactory agreement with theoretical results for mixture of MetHb, COHb, and oxyhemoglobin. The method was compared with two other methods using 55 forensic blood samples containing various amounts of MetHb and COHb, and proved to be suitable for practical samples.

Blepharismin produced by a protozoan Blepharisma functions as an antibiotic effective against methicillin-resistant Staphylococcus aureus

A ciliated protozoan, Blepharisma japonicum, produces a photosensitive red pigment, blepharismin (BLR). This study showed that the pigment inhibits the growth of Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) resistant to arbekacin (ABK), which is the most effective aminoglycoside antibiotic against MRSA and used world wide. Although the minimum inhibitory concentration (MIC) of BLR to the ABK-resistant MRSA strain was 6.25 micrograms/ml in dark, it was decreased to 1.25 micrograms/ml by irradiation with white light of 65 W/m2 for 30 min, suggesting that the antibacterial activity of BLR is photoactivated. Our findings suggested that the antibacterial activity of BLR in dark is due to inhibition of protein synthesis. In addition, we found that BLR is bactericidal and enhances synergistically the antibacterial activity of ABK.

[Lymph node dissection during a video-assisted lobectomy is inferior to that in a standard lobectomy]

The indications for a video-assisted lobectomy are currently ill-defined. Clinicians recommend based on the extent of lymph node involvement. Fifty-nine patients with clinical stage I non-small cell lung cancer underwent lobectomies with systemic lymph node dissections through a standard thoracotomy (Group C), and 26 patients underwent lobectomies with lymph node dissections using the video-assisted procedure (Group V). The number of dissected lymph nodes at all node levels were compared between the two groups. There was no significant difference between groups in the total number of dissected lymph nodes in patients with right lung cancer. The number of dissected hilar and interlobar lymph nodes, however, was less in Group V than that in Group C (hilar: 1.2 +/- 0.4 vs. 2.8 +/- 0.6, interlobar: 1.1 +/- 0.4 vs. 2.1 +/- 0.4). The total number of dissected lymph nodes in patients with left lung cancer was significantly less in Group V than that in Group C (18.5 +/- 0.3 vs. 28.7 +/- 2.4). In addition, the number of dissected lymph nodes in pratracheal, pretracheal, tracheobronchial, subcarinal, hilar, and interlobar lymph nodes were significantly less in the group V than those in Group C. Although there was no significant difference in the actual survival rates between the groups in this preliminary study, a sufficiently small number of dissected lymph nodes in the video-assisted lobectomy may have resulted in inaccurate staging and poor prognosis in these patients.

Malignant solitary fibrous tumor arising in the right buttock associated with metastatic parietal pleural and intrapulmonary tumors in addition to pleural effusion

A malignant solitary fibrous tumor arising in the right buttock associated with metastatic parietal pleural and intrapulmonary tumors and pleural effusion was found in a 59-year-old man. A chest computed tomogram revealed three tumors attached to the parietal pleura with rib destruction, and a tumor in the left lower lung field. Histologically, the tumors of the buttock and parietal pleura were characterized by proliferation of bundles of spindle-shaped or oval cells separated by wavy hyalinized collagen tissue with no expression of cytokeratin, S-100 protein, muscle actin or epithelial membrane antigen, but these cells weakly expressed CD34 and strongly expressed vimentin.

A serum factor potentiates ACh and AMPA receptor currents via differential signal transduction pathways

A serum factor is recognized to interact with a protein kinase C (PKC) pathway. Indeed, treatment with fetal bovine serum enhanced ACh-evoked currents by PKC activation in the neuronal nicotinic ACh receptors (alpha7) and Torpedo ACh receptors expressed in Xenopus oocytes. In addition, potentiation of ACh-evoked currents induced by fetal bovine serum was observed also in the mutant Torpedo ACh receptors lacking potent PKC phosphorylation sites at Ser333 on the alpha subunit and Ser377 on the delta subunit; the potentiation was inhibited by the PKC inhibitor, PKC inhibitor peptide (PKCI), indicating that ACh receptor currents were enhanced by PKC activation but not by PKC phosphorylation of the receptors. On the other hand, fetal bovine serum enhanced kainate-evoked currents in oocytes expressing the alpha-amino3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, GluR1,3. The enhancement was not affected by the PKC inhibitors, PKCI or GF109203X, and instead, was inhibited by the Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor, KN-62. These results suggest that serum is not only involved in PKC activation but in CaMKII activation, and that thereby ACh receptor currents and AMPA receptor currents are each potentiated.

Analysis of 2,702 traumatized patients in the 1995 Hanshin-Awaji earthquake

BACKGROUND

This study was undertaken to define the factors that affected the final outcome of trauma patients in the Hanshin-Awaji earthquake.

METHODS

Medical records of patients admitted to 95 hospitals within or surrounding the affected area during the first 15 days after the quake were reviewed.

RESULTS

There were 2,702 traumatized patients. One-third of the patients were transported to hospitals in the surrounding area and had a mortality rate of 3%. The remainder, who were treated in the affected hospitals, showed a significantly higher mortality rate (8%; p < 0.05). Intensive care was provided for 513 patients, most of whom suffered from crush syndrome or from injuries to vital organs; these patients had a high mortality rate. Patients with other types of injuries had a lower mortality rate.

CONCLUSION

Crush syndrome and injuries to vital organs were potentially life-threatening. We believe that early transportation of such patients to undamaged hospitals with the ability to provide intensive care would have improved the survival rate.

Aberrant gastric venous drainage into the medial segment: demonstration by color Doppler sonography

BACKGROUND

Aberrant gastric venous drainage (AGVD) into the posterior edge of the medial segment of the liver (segment IV) is the main cause of pseudolesion on computed tomography (CT) during arterial portography. We estimated the prevalence of AGVD into the medial segment of the liver with color and power Doppler ultrasound (US).

METHODS

Screening gray-scale and color Doppler and power Doppler US were performed in 100 consecutive patients. AGVD was defined as a venous structure that ascended parallel to the main portal vein and drained independently into segment IV.

RESULTS

AGVDs were observed in eight of 100 patients (8%) with color and power Doppler US. Power Doppler US depicted these veins more clearly than did color Doppler US. Gray-scale US did not show any AGVDs. Two of eight patients with AGVDs detected by color Doppler US underwent celiac arteriography and CT during arterial portography (CTAP). In these two patients, celiac arteriography directly demonstrated AGVDs draining into segment IV, which revealed nontumorous perfusion defects (pseudolesions) on CTAP.

CONCLUSION

Color and power Doppler US are useful imaging methods for demonstrating AGVDs.

The GABAA receptor is expressed in human neurons derived from a teratocarcinoma cell line

NT2 cells, a human teratocarcinoma cell line, are shown to be differentiated in neuron-like cells (NT2-N cells) by treatment with retinoic acid. The present study identified the neurotransmitter receptors expressed in NT2-N cells using patch-clamp recording. Voltage-sensitive Na+ currents, which are specific for neurons, were observed in NT2-N cells but not in NT2 cells, suggesting that NT2-N cells actually function as neurons. Glutamate receptor agonists, N-methyl-D-aspartate (NMDA) and kainate, evoked whole-cell currents. In addition, gamma-aminobutyric acid (GABA) evoked currents and the currents were inhibited by the selective GABAA receptor antagonist, bicuculline. In outside-out patches, GABA elicited single channel currents with two classes of the slope conductance (26 and 50 pS). No current, however, was induced by ACh, serotonin, or dopamine NT2-N cells, thus, express at least two types of the major excitatory and inhibitory neurotransmitter receptor in the central nervous system, the glutamate and GAGAA receptors, suggesting that these receptors have a crucial role in neurotransmission from the earlier stage of the brain development.

Altered pain perception and inflammatory response in mice lacking prostacyclin receptor

Prostanoids are a group of bioactive lipids working as local mediators and include D, E, F and I types of prostaglandins (PGs) and thromboxanes. Prostacyclin (PGI2) acts on platelets and blood vessels to inhibit platelet aggregation and to cause vasodilatation, and is thought to be important for vascular homeostasis. Aspirin-like drugs, including indomethacin, which inhibit prostanoid biosynthesis, suppress fever, inflammatory swelling and pain, and interfere with female reproduction, suggesting that prostanoids are involved in these processes, although it is not clear which prostanoid is the endogenous mediator of a particular process. Prostanoids act on seven-transmembrane-domain receptors which are selective for each type. Here we disrupt the gene for the prostacyclin receptor in mice by using homologous recombination. The receptor-deficient mice are viable, reproductive and normotensive. However, their susceptibility to thrombosis is increased, and their inflammatory and pain responses are reduced to the levels observed in indomethacin-treated wild-type mice. Our results establish that prostacyclin is an antithrombotic agent in vivo and provide evidence for its role as a mediator of inflammation and pain.

Continuous infusion of 5-fluorouracil and low dose cisplatin infusion for the treatment of advanced and recurrent gastric adenocarcinoma

BACKGROUND

Several chemotherapy studies have suggested that continuous infusion of 5-fluorouracil (5-FU) is more effective than bolus 5-FU. In addition, 5-FU and cis-Diamminedichloroplatinum-II (cisplatin) in combination have been shown to have synergistic cytotoxicity against several human neoplasms. In this study, the authors evaluated the efficacy and toxicity of continuous infusion of 5-FU and low dose cisplatin infusion (FP therapy) in the treatment of advanced and recurrent gastric adenocarcinoma. The relationship between the response to FP therapy and several factors was also examined.

METHODS

A total of 26 patients fulfilling standard eligibility criteria were enrolled in the trial. FP therapy consisted of 5-FU (350 mg/m2/day every day by continuous infusion) and cisplatin (7.5 mg/m2/day in 100 mL of normal saline infused over 1 hour on Days 1-5 every week) for 4 weeks.

RESULTS

A complete response was observed in 2 cases and a partial response in 11 cases, for an overall response rate of 50%. Patients with good performance status (PS) (0-1) and differentiated histologic type showed higher response rates (50.0% and 63.6%, respectively) than patients with poor PS (2 or 3) and undifferentiated histologic type (28.6% and 35.3%, respectively), although there were no significant differences. Patients with low serum levels of immunosuppressive acidic protein (IAP) showed a significantly higher response rate (71.4%) than those with high IAP levels (0%). Toxic effects included leukopenia, thrombocytopenia, nausea, and vomiting; these were not life-threatening and did not require treatment interruption.

CONCLUSIONS

FP therapy is a promising regimen for patients with advanced and recurrent gastric adenocarcinoma. Serum levels of IAP may predict chemosensitivity.

Burn injuries in the 1995 Hanshin-Awaji earthquake

In the 1995 Hanshin-Awaji earthquake, 504 deaths were listed as fire related, although many of the victims may have been crushed or suffocated before they were burned. Census data related to surviving burn victims, however, were unknown. This study was designed to examine the medical requirements of those burn patients following the earthquake. Medical records of 2718 patients with injuries admitted to 95 hospitals during the 15 days after the earthquake were retrospectively reviewed. Only 44 patients (1.9 per cent) were hospitalized with burns. Scalds with less than 20 per cent total burn surface area (TBSA) were mainly observed; flame burns from earthquake-associated fires were rare. Morbidity rates increased in patients over 40 years old. Associated injuries were observed in 11 cases. These included three soft tissue injuries, one rib, three spine, three pelvis and two extremity fractures, and two cases of crush syndrome. Intensive care was required for only 10 patients, five of whom were transferred to hospitals that were undamaged or outside the earthquake zone. No relationship was noted between the number of burned houses and that of hospitalized burn patients. These results suggest that the number of burn patients requiring medical care was less than might have been expected in view of the total number of fire-related deaths in this urban earthquake.

Subthreshold hyperoxia potentiates TNF-alpha-induced ICAM-1 expression on cultured pulmonary microvascular endothelial cells

The effects of combined exposure to subthreshold hyperoxia and the inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) on the expression of intercellular adhesion molecule-1 (ICAM-1) were examined in bovine lung microvascular endothelial cells (BLuEC). The expression of total ICAM-1 was not affected by 50% hyperoxia conditions alone, indicating that this level is subthreshold for BLuEC. In the presence of 5 ng/mL TNF-alpha, which has minimal influence on BLuEC alone, the amount of total ICAM-1 expression under 50% hyperoxia was higher than that in normoxic conditions (approximately 30%) throughout the culture period. The amount of soluble ICAM-1 that has been released into the culture medium increased after joint exposure to hyperoxia and TNF-alpha. These results suggest that exposure to subthreshold hyperoxia, which does not by itself cause damage to the endothelial cells or induce ICAM-1 expression, potentiates the effects of low-level TNF-alpha exposure.

Long-lasting enhancement of ACh receptor currents by lysophospholipids

Lysophosphatidylcholine (LysoPtdCho) and lysophosphatidylethanolamine (LysoPtdEtn), which are formed by phospholipase A2-catalyzed hydrolysis of phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn), respectively, are proposed to be involved in protein kinase C (PKC) activation. Their physiological significance, however, remains unclear. We examined the effects of lysoPtdCho and lysoPtdEtn on acetylcholine (ACh) receptor currents using oocytes expressing Torpedo nicotinic ACh receptors. LysoPtdCho enhanced the currents in a washing time- and dose-dependent manner (10 nM-1 microM), reaching a maximum of 191% at 20 min after treatment. The currents were enhanced to a lesser extent at higher concentrations, and instead, inhibited to 81% at 10 microM. Likewise, lysoPtdEtn also potentiated the currents to 200% at 10 microM, although its dose-dependent curve shifted to right as compared with that of lysoPtdCho. The current potentiation was blocked by a PKC inhibitor, PKC inhibitor peptide (PKCI), or removal of extracellular Ca2+. In addition, lysoPtdCho and lysoPtdEtn enhanced the currents in mutant ACh receptors lacking PKC phosphorylation sites on the alpha and delta subunits. These results suggest that lysophospholipids such as lysoPtdCho and lysoPtdEtn potentiated ACh receptor currents by Ca2+-dependent PKC activation, but that this effect did not require PKC phosphorylation of the ACh receptor.

Involvement of SNAP-25 in TRH-induced exocytosis in pituitary GH4C1 cells

The synaptic membrane protein synaptosomal-associated protein (SNAP-25) has recently been implicated as one of the key proteins involved in exocytotic membrane fusion in neurons. However, the role of SNAP-25 in pituitary hormone release is not known. In this study, we determined that SNAP-25 is involved in regulated exocytosis in the clonal pituitary cell line GH4C1. SNAP-25 messenger RNA and protein were detected in GH4C1 cells by RT-PCR and immunoblot analysis, respectively. Immunofluorescence analysis indicated that SNAP-25 protein was localized in the plasma membrane. Next, to determine the function of SNAP-25 in GH4C1 cells, specific inhibitors of SNAP-25, botulinum neurotoxin (BoNT)/A or /E, and antisense SNAP-25 oligonucleotide were used. Neither BoNT/A nor BoNT/E affected thyrotropin-releasing hormone (TRH)-induced cytosolic Ca2+ increase, but both inhibited TRH-induced exocytosis. Moreover, they dose-dependently inhibited TRH-induced prolactin release. The introduction of antisense oligonucleotide into the cells also inhibited TRH-induced prolactin release. These results suggest that SNAP-25 is involved in regulated exocytosis in GH4C1 cells.

Dermatophagoides farinae-1-derived peptides and HLA molecules recognized by T cells from atopic individuals

Der f 1, the group I allergen in Dermatophagoides farinae extracts, is a major source of inhalation allergens in Japan. Using the mixture of a panel of overlapping synthetic peptides that spread over the entire Der f 1 molecule, we found that polyclonal Der f 1-specific short-term T cell lines prepared from peripheral blood of 6 individuals allergic to Der f who carry most of the common HLA haplotypes seen in the Japanese population can respond to 16 different peptides. Eight of 16 peptides stimulated T cells of more than 2 donors, regardless of the HLA types. Proliferative responses of four T cell lines were markedly inhibited by mAb HU4 (anti-HLA-DRB1+B5), one was inhibited partially by HU11 (anti-HLA-DQ4+5+6), and one was inhibited fully by a combination of HU4, L243 (anti-HLA-DRB1+B4) and PLM16 (anti-HLA-DRB3) but only partially by each of these mAbs. One of these T cell lines, DT, of which the proliferative response was partially inhibited by HU11, was cloned. Indeed, the T cell clones were restricted by DQ6 molecules on an HLA-DRB1*1501-DRB5*0101-DQA1*0102-DQB1*0602 haplotype. These results indicate that patients' T cells recognize Der f 1 in association mainly with HLA-DRA/DRB1, but that DQAI/DQB1, DRA/DRB3 and possibly DRA/DRB4 gene products also function as antigen-presenting molecules. Thus, although some peptides have a more potent T cell-stimulatory activity than others, the T cell receptor ligands formed with the Der f 1 molecule are highly heterogeneous.

Short-term depression and long-term enhancement of ACh-gated channel currents induced by linoleic and linolenic acid

The effects of cis-unsaturated free fatty acids such as linoleic and linolenic acid on ACh-evoked currents were examined using normal and mutant nicotinic acetylcholine (ACh) receptors lacking protein kinase C (PKC) phosphorylation sites on the alpha and delta subunits expressed in Xenopus oocytes. These free fatty acids reduced ACh-gated channel currents during treatment and to a greater extent in Ca2+-free extracellular solution. After treatment, the currents were enhanced as the drug was washed out, but this effect was not observed in the absence of extracellular Ca2+. Linolenic acid was more potent of the current enhancement (300% of the control) than linoleic acid (190% of the control). The current enhancement induced by these free fatty acids was inhibited by the selective PKC inhibitor, GF109203X, while the current depression was not affected. Furthermore, these lipids decreased ACh-evoked currents in mutant ACh receptors to the same extent as in normal ACh receptors, but never enhanced the currents. These results indicate that linoleic and linolenic acid have biphasic actions on ACh receptor currents; a short-term depression and a long-term enhancement. The short-term depression may be due to an interaction with the ACh receptor channels, presumably at Ca2+ binding sites. The long-lasting enhancement appears to result from Ca2+-dependent PKC activation followed by PKC phosphorylation of the ACh receptors.