Dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux in vivo.

The purpose of this study was to determine whether dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux from the in situ hamster cheek pouch and, if so, whether this response is specific. By using intravital microscopy, we found that an aqueous extract of grain sorghum dust elicited significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (FITC-dextran; mol mass, 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated substance P-induced leaky site formation and increase in clearance of FITC-dextran from the cheek pouch but had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on arteriolar diameter in the cheek pouch. On balance, these data indicate that dexamethasone attenuates grain sorghum dust extract- and substance P-induced increases in macromolecular efflux from the in situ hamster cheek pouch in a specific fashion.     

Dexamethasone attenuates acute macromolecular efflux increase evoked by smokeless tobacco extract.

The purpose of this study was to determine whether dexamethasone attenuates the acute increase in macromolecular efflux from the oral mucosa elicited by an aqueous extract of smokeless tobacco (STE) in vivo, and, if so, whether this response is specific. Using intravital microscopy, we found that 20-min suffusion of STE elicited significant, concentration-related leaky site formation and an increase in clearance of fluorescein isothiocyanate-labeled dextran (FITC-dextran; mol mass 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated the bradykinin-induced leaky site formation and the increase in clearance of FITC-dextran from the cheek pouch. However, it had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on baseline arteriolar diameter and on bradykinin-induced vasodilation in the cheek pouch. Collectively, these data indicate that dexamethasone attenuates, in a specific fashion, the acute increase in macromolecular efflux from the in situ oral mucosa evoked by short-term suffusion of STE. We suggest that corticosteroids mitigate acute oral mucosa inflammation elicited by smokeless tobacco.     

Adenosine A(1) receptors mediate plasma exudation from the oral mucosa.

The purpose of this study was to pharmacologically characterize the adenosine receptor subtype(s) that mediates adenosine-induced increases in macromolecular efflux from the intact hamster cheek pouch. Using intravital microscopy, we found that 1,3-dipropyl-8-(2-amino-4-chlorophenyl)-xanthine (PACPX), a selective adenosine receptor-1 antagonist, but not 3,7-dimethyl-1-propargylxanthine (DMPX), a selective adenosine receptor-2 antagonist, significantly attenuated adenosine-induced leaky site formation and increased clearance of fluorescein isothiocyanate-labeled dextran (molecular mass, 70 kDa) from the intact hamster cheek pouch (P < 0.05). Both compounds had no significant effects on bradykinin-induced responses. Nanomolar concentrations of R(-)-N(6)-(2-phenylisopropyl)-adenosine [R(-)-PIA], a selective adenosine A(1) agonist, evoked significant, concentration-dependent increases in macromolecular efflux. This response was significantly attenuated by PACPX but not by DMPX. In contrast, CGS-21680, a selective adenosine A(2) agonist, increased macromolecular efflux but only at micromolar concentrations. This response was significantly attenuated by DMPX but not by PACPX. Suffusion of nitroglycerin had no significant effects on R(-)-PIA- and CGS-21680-induced responses. In addition, suffusion of N(G)-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, had no significant effects on adenosine-induced responses. Indomethacin had no significant effects on adenosine-, R(-)-PIA-, and CGS-21680-induced increases in macromolecular efflux. Collectively, these data indicate that adenosine increases macromolecular efflux from the intact hamster cheek pouch by stimulating high-affinity adenosine A(1) receptors in a specific, nitric oxide- and prostaglandin-independent fashion.     

Bradykinin- and substance P-induced edema formation in the hamster cheek pouch is tyrosine kinase dependent.

The purpose of this study was to determine whether protein tyrosine kinase, a ubiquitous family of intracellular signaling enzymes that regulates endothelial cell function, modulates bradykinin- and substance P-induced increase in macromolecular efflux from the intact hamster cheek pouch microcirculation. Using intravital microscopy, I found that suffusion of bradykinin or substance P (each, 0.5 and 1.0 microM) onto the cheek pouch elicited significant, concentration-dependent leaky site formation and increase in clearance of fluorescein isothiocyanate-dextran (FITC-dextran; molecular mass, 70 kDa; P < 0.05). These responses were significantly attenuated by suffusion of genistein (1.0 microM) or tyrphostin 25 (10 microM), two structurally unrelated, nonspecific protein tyrosine kinase inhibitors (P < 0.05). Conceivably, the kinase(s) involved in this process could be agonist specific because genistein was more effective than tyrphostin 25 in attenuating bradykinin-induced responses while the opposite was observed with substance P. Both inhibitors had no significant effects on adenosine (0.5 M)-induced responses (P > 0.5). Collectively, these data suggest that the protein tyrosine kinase metabolic pathway modulates, in part, the edemagenic effects of bradykinin and substance P in the intact hamster cheek pouch microcirculation in a specific fashion.     

Purified ACE attenuates smokeless tobacco-induced increase in macromolecular efflux from the oral mucosa

Gao, Xiao-pei, Hideyuki Suzuki, Christopher O. Olopade,Sergei Pakhlevaniants, and Israel Rubinstein. Purified ACE attenuates smokeless tobacco-induced increase in macromolecular effluxfrom the oral mucosa. J. Appl.Physiol. 83(1): 74-81, 1997.The purpose of thisstudy was to determine whether purified angiotensin I-converting enzyme(ACE) attenuates smokeless tobacco extract (STE)-induced increase inmacromolecular efflux from the in situ oral mucosa. Byusing intravital microscopy, we found that suffusion of an aqueousextract of smokeless tobacco elicited significant concentration-dependent leaky site formation and increase in clearance of fluorescein isothiocyanate-labeled dextran (mol mass, 70 kDa) fromthe hamster cheek pouch (P < 0.05). Suffusion of purified rabbit lung ACEsignificantly attenuated these responses in a concentration-dependentfashion (P < 0.05). These effectswere specific because purified ACE also significantly attenuated the increase in macromolecular efflux elicited by bradykinin, which isproduced in the cheek pouch during suffusion of STE, but did notattenuate the increase elicted by adenosine. Moreover,suffusion of heat-inactivated purified ACE and purified superoxidedismutase had no significant effects on STE- andbradykinin-induced responses. Collectively, these data suggestthat exogenous ACE attenuates STE-induced increase in macromolecularefflux from the in situ oral mucosa, in part, by promoting localbradykinin catabolism.

     

Human galanin expresses amphipathic properties that modulate its vasoreactivity in vivo

The purpose of this study was to determine whether human galanin, a pleiotropic 30-amino acid neuropeptide, expresses amphipathic properties in vitro and, if so, whether these properties modulate its vasoactive effects in the intact peripheral microcirculation. We found that human galanin aggregates in an aqueous solution and forms micelles with a critical micellar concentration (CMC) of 0.4 microM. In addition, the peptide interacted with model membrane as indicated by long and significant increase of the surface pressure of the biomimetic monolayer membrane in vitro. Interactions of human galanin with sterically stabilized phospholipid micelles (SMM) were not associated with a significant change in peptide conformation. Using intravital microscopy, we found that suffusion of human galanin alone elicited significant concentration-dependent vasoconstriction in the intact hamster cheek pouch. This response was amplified when human galanin in SSM was suffused onto the cheek pouch. The effects of human galanin alone and in SSM were mediated by galanin receptors because galantide, a galanin receptor antagonist, abrogated galanin-induced vasoconstriction. Collectively, these data show that human galanin expresses amphipathic properties in the presence of phospholipids which in turn amplifies its vasoactive effects in the intact peripheral microcirculation.     

Tyrosine kinase inhibitors modulate agonist-induced vasodilation in the hamster cheek pouch.

The purpose of this study was to determine whether inhibitors of tyrosine kinase attenuate vasodilation elicited by endogenously elaborated and exogenously applied nitric oxide in the in situ peripheral microcirculation. Using intravital microscopy, we found that pretreatment with genistein (1.0 microM) and tyrphostin 25 (10.0 microM), two structurally unrelated tyrosine kinase inhibitors, significantly attenuated acetylcholine-, bradykinin- and nitroglycerin-induced dilation of second-order arterioles (51 +/- 1 microm) in the in situ hamster cheek pouch (P < 0.05). Both inhibitors nearly abrogated acetylcholine-induced responses but only partially blocked bradykinin- and nitroglycerin-induced vasodilation. Genistein and tyrphostin 25 alone had no significant effects on resting arteriolar diameter and on adenosine-induced vasodilation in the cheek pouch. On balance, these data indicate that tyrosine kinase inhibitors attenuate endogenously elaborated and exogenously applied nitric oxide-induced vasodilation in the in situ hamster cheek pouch. However, the extent of tyrosine kinase inhibitor-sensitive pathway involvement in this response appears to be agonist dependent.     

All D-VIP mitigates vasodilation elicited by L-VIP, micellar L-VIP and micellar PACAP1-38, but not PACAP1-38, in vivo

The purpose of this study was to determine whether all D-vasoactive intestinal peptide (VIP), an inactive optical isomer of L-VIP, modulates the vasorelaxant effects of human L-VIP and pituitary adenylate cyclase activating peptide (PACAP)1-38, two ubiquitous and pleiotropic neuropeptides that activate VPAC1 and VPAC2, two VIP subtype receptors, in the intact peripheral microcirculation. Using intravital microscopy, we found that suffusion of all D-VIP had no significant effects on arteriolar diameter in the intact hamster cheek pouch. However, all D-VIP significantly attenuated L-VIP-induced vasodilation in a concentration-dependent fashion (P<0.05). likewise, all D-VIP significantly attenuated the vasorelaxant effects of L-VIP associated with sterically stabilized phospholipid micelles (SSM; P<0.05). Although all D-VIP had no significant effects on L-PACAP1-38-induced vasodilation, it abrogated PACAP1-38 in SSM-induced responses (P<0.05). The effects of all D-VIP were specific because it had no significant effects on acetylcholine-, nitroglycerin- and bradykinin-induced vasodilation. Taken together, these data indicate that all D-VIP attenuates the vasorelaxant effects of random coil and alpha-helix L-VIP as well as those of alpha-helix but not random coil PACAP in the intact peripheral microcirculation in a specific fashion. These effects are mediated, most likely, through interactions with VPAC1/VPAC2 receptors. We suggest that all D-VIP could be exploited as a novel, safe and active targeting moiety of VPAC1/VPAC2 receptors in vivo.     

Hog barn dust extract augments lymphocyte adhesion to human airway epithelial cells.

The dust of hog confinement facilities induces airway inflammation. Mechanisms by which this dust modulates inflammation are not completely defined, although it is clear that exposure to dust can modulate both epithelial cell and inflammatory cell function. In this work, we demonstrate that airway epithelial cell (BEAS-2B) treatment with hog barn dust extract (HDE) results in augmentation of peripheral blood lymphocyte adhesion to epithelial cell cultures in vitro. The augmentation of lymphocyte adhesion to epithelial cells is dependent on the concentration of HDE and time of HDE exposure, with twofold increases observed by 3 h and maintained at 24 h. Similar results are seen with primary human bronchial epithelial cells in culture. Lymphocyte adhesion to epithelial cells is inhibited in a concentration-dependent fashion by the treatment of epithelial cells with antibody to intercellular adhesion molecule-1 (ICAM-1). In addition, HDE exposure of epithelial cells results in an approximate twofold increase in ICAM-1 expression as determined by flow cytometry analysis. Pretreatment of epithelial cells with a protein kinase C-alpha (PKC-alpha) inhibitor, G?-6976, also inhibited subsequent lymphocyte adhesion to HDE-exposed epithelial cells. These data suggest that airway epithelial cell HDE exposure enhances subsequent lymphocyte adhesion to epithelial cells that is mediated in part by HDE modulation of ICAM-1 expression and PKC-alpha.     

Effect of cigarette smoke extract on arteriolar dilatation in vivo

Mayhan, William G., and Glenda M. Sharpe. Effect ofcigarette smoke extract on arteriolar dilatation in vivo.J. Appl. Physiol. 81(5):1996-2003, 1996.The goal of this study was to determine whethercigarette smoke extract alters dilatation of arterioles in vivo inresponse to agonists that produce activation of ATP-sensitive potassiumchannels and activation of adenylate cyclase. By using intravitalmicroscopy, we measured diameter of arterioles contained within themicrocirculation of the hamster cheek pouch during suffusion withagonists in the absence and presence of cigarette smoke extract (0.1, 0.5, and 1.0%). Before treatment with cigarette smoke extract,activation of ATP-sensitive potassium channels with aprikalim andcromakalim produced dose-related dilatation of cheek poucharterioles. Similarly, activation of adenylate cyclasewith isoproterenol and forskolin produced dose-related dilatation ofcheek pouch arterioles before treatment with cigarette smoke extract.Superfusion of 0.1% cigarette smoke extract did not change baselinediameter of arterioles and did not alter responses of cheek poucharterioles to activation of ATP-sensitive potassium channels andadenylate cyclase. Superfusion of 0.5 and 1.0% cigarette smoke extractalso did not alter baseline diameter of arterioles but did impairdilatation of arterioles in response to activation of ATP-sensitivepotassium channels and adenylate cyclase. These findings suggest thatcigarette smoke extract impairs dilatation of resistance arterioles inresponse to activation of important cellular dilator pathways.

     

Interactions of VIP with rigid phospholipid bilayers: implications for vasoreactivity

The purpose of this study was to determine whether vasoactive intestinal peptide (VIP), a pleiotropic amphipathic peptide, interacts with rigid liposomes composed of gel phase phospholipids. We found that incubation of VIP with small unilamellar gel phase liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and egg phosphatidylglycerol (ePG) for 2h at room temperature had no significant effects on VIP secondary structure. Moreover, suffusion of VIP (0.01, 0.1 and 1.0nmol) incubated in saline or with DPPC/ePG liposomes (size, 30 and 100nm) for 2h at room temperature or 4 degrees C onto the intact hamster cheek pouch microcirculation elicited a similar concentration-dependent vasodilation except for 0.01nmol VIP (P<0.05). By contrast, incubation of VIP with gel phase liposomes overnight at 4 degrees C significantly potentiated vasodilation evoked by all three concentrations of the peptide in comparison to aqueous VIP (P<0.05). VIP-induced vasodilation was liposome size-independent. The ratio of VIP to phospholipids in DPPC/ePG liposomes was concentration-independent. Collectively, these data indicate that short-term interactions of VIP with rigid phospholipid bilayers are limited resulting in only modest effects on VIP vasoreactivity in vivo.     

Helospectin I and II evoke vasodilation in the intact peripheral microcirculation

Helospectin I and II, two closely related mammalian neuropeptides of the secretin/glucagons/vasoactive intestinal peptide (VIP) superfamily of peptides, are co-localized with VIP in nerve fibers surrounding vascular smooth muscle. However, the role if any, VIP receptors play in transducing the vasorelaxant effects of helospectin I and II in the intact peripheral microcirculation is uncertain. The purpose of this study was to determine whether helospectin I and II elicit vasodilation in the intact peripheral microcirculation and, if so, whether this response is mediated, in part, by VIP or pituitary adenylate cyclase activating peptide (PACAP) receptor engagement, and through local elaboration of cyclooxygenase products of arachidonic acid metabolism. Using intravital microscopy, we found that suffusion of helospectin I and II (each, 1.0 nmol) evoked potent vasodilation and of similar magnitude in the intact hamster cheek pouch microcirculation (P < 0.05). Suffusion of 0.1 nmol helospectin I and II had no significant effects on arteriolar diameter. Pretreatment with VIP(10-28), a VPAC1/VPAC2 receptor antagonist, or PACAP(6-38), a PAC1/VPAC2 receptor antagonist, had no significant effects on helospectin I- and II-induced responses. In addition, pretreatment with indomethacin had no significant effects on helospectin I- and II-induced vasodilation. Collectively, these data indicate that helospectin I and II evoke potent vasodilation in the intact peripheral microcirculation that is not transduced by VIP or PACAP receptors nor through cyclooxygenase products of arachidonic acid metabolism.     

Effects of Pseudomonas aeruginosa endotoxin on vasodilation in the intact spinotrapezius muscle.

The purpose of this study was to determine whether short-term exposure to clinically relevant concentrations of Pseudomonas aeruginosa lipopolysaccharide (LPS) impairs vasoreactivity of resistance arterioles in the intact spinotrapezius muscle microcirculation and, if so, to determine the mechanisms mediating this response. Using intravital microscopy, we found that 60-min suffusion of P. aeruginosa LPS (0.03-3.0 microg/ml) on the in situ hamster spinotrapezius muscle elicited an immediate, profound, and prolonged concentration-dependent vasodilation (P < 0.05). This response was reversible once suffusion of P. aeruginosa LPS was stopped. Pretreatment with N(G)-nitro-L-arginine methyl ester (10.0 microM), a nonselective nitric oxide (NO) synthase inhibitor, but not N(G)-nitro-D-arginine methyl ester, abrogated P. aeruginosa LPS-induced vasodilation and elicited a small, albeit significant, vasoconstriction. Indomethacin had no significant effects on P. aeruginosa LPS-induced responses. P. aeruginosa LPS had no significant effects on acetylcholine- and nitroglycerin-induced vasodilation in the spinotrapezius muscle. Collectively, these data indicate that short-term exposure to clinically relevant concentrations of P. aeruginosa LPS evokes an immediate, potent, prolonged, and reversible NO-dependent, prostaglandin-independent vasodilation in skeletal muscles in vivo. We suggest this response could play an important role in the pathophysiology of the profound vasomotor dysfunction observed in the peripheral circulation of patients with P. aeruginosa sepsis syndrome.     

Modification of postischemic increase of leukocyte adhesion and vascular permeability in the hamster by Iloprost.

This study of the postischemic events in the hamster cheek pouch showed that there is an increase in number of leukocytes adhering to the venular endothelium after reperfusion. It also showed that the stable prostacyclin analogue Iloprost could counteract both the postischemic increase in leukocyte adhesion and the postischemic increase in vascular permeability to macromolecules. The hamsters were anesthetized and the cheek pouch was everted and prepared for intravital microscopy. Temporary ischemia (30 min) was obtained using an expandable cuff placed around the proximal part of the cheek pouch. Fluorescein labelled dextran (FITC-dextran, Mw 150,000) was used as a tracer of macromolecular leakage from the postcapillary venules. Iloprost, given either topically (0.1 nM) or as an intravenous infusion (40 ng/kg/min), reduced the postischemic permeability increase (P less than 0.05) but did not affect the hemodynamics or the permeability response induced by histamine. It is proposed that these effects could be due to inhibition of leukocyte activation by Iloprost, indicating that these cells could play a role in the permeability increase during reperfusion after ischemia.     

Atriopeptin does not augment the transvascular flux of macromolecules in the hamster cheek pouch.

Natriuretic peptides elaborated by atrial myocytes promote marked renal sodium and water excretion as a mechanism for fluid and electrolyte balance. Recent evidence suggests that atriopeptin (ANP) also targets the non-renal vasculature as a site for enhanced fluid exchange. It remains unclear whether ANP alters microvascular integrity to facilitate the efflux of both plasma and proteins across the endothelial barrier, or if fluid exchange is selectively enhanced. This study evaluated the influence of ANP on macromolecular transport through the direct observation of microvessels in the hamster cheek pouch using fluorescent intravital microscopy. Fluorescein isothiocyanate conjugated to either bovine serum albumin or dextran 150,000 Mw was utilized as a permeability probe. Macromolecular efflux was quantified as fluorochrome clearance. The clearance of fluorescein-conjugated bovine serum albumin (57.94 +/- 7.03) or fluorescein-conjugated dextran 150 (4.09 +/- 1.35) remained unaltered by intravascular injection of 1 microgram/kg ANP. Topical application of 40 ng to cheek pouch microvessels produced similar results. All pouches demonstrated positive leakage response to histamine 2.5 x 10(-6) M, increasing fluorochrome clearance approximately 2- to 11-fold. Bolus injection of 1 microgram/kg ANP reduced mean arterial pressure, increased urine flow from 6.63 +/- 2.59 microliters/min to 8.20 +/- 6.13 microliters/min, and elevated sodium excretion from 1.37 +/- 0.49 microEq/min to 2.54 +/- 0.99 microEq/min. These results suggest that ANP fails to significantly alter the integrity of the protein-transporting channels in the microvascular exchange barrier.     

Grain sorghum dust increases macromolecular efflux from the in situ nasal mucosa

The purpose of this study was to determine whether an aqueousextract of grain sorghum dust increases macromolecular efflux from thenasal mucosa in vivo and, if so, whether this response is mediated, inpart, by substance P. Suffusion of grain sorghum dust extract on the insitu nasal mucosa of anesthetized hamsters elicits a significantincrease in clearance of fluorescein isothiocyanate-labeled dextran(FITC-dextran; mol mass, 70 kDa; P < 0.05). This response is significantly attenuated byCP-96345 and RP-67580, two selective, but structurally distinct,nonpeptide neurokinin 1 (substance P)-receptor antagonists, but not byCP-96344, the2R,3Renantiomer of CP-96345 (P < 0.05). CP-96345 has no significant effects on adenosine-induced increase in clearance of FITC-dextran from the insitu nasal mucosa. CP-96345 and RP-67580, but not CP-96344, significantly attenuate substance P-induced increases in clearance ofFITC-dextran from the in situ nasal mucosa(P < 0.05). Collectively, these datasuggest that grain sorghum dust elicits neurogenic plasma exudationfrom the in situ nasal mucosa.

     

PGH(2)-TxA(2)-receptor blockade restores vasoreactivity in a new rodent model of genetic hypertension.

The purpose of this study was to determine whether activation of prostaglandin H(2)-thromboxane A(2) (PGH(2)-TxA(2)) receptors impedes vasodilation in the in situ peripheral microcirculation of spontaneously hypertensive hamsters, a new rodent model of high-renin genetic hypertension. Using intravital microscopy, we found that vasodilation elicited by suffusion of acetylcholine and vasoactive intestinal peptide (VIP), two neurotransmitters localized in perivascular nerves in the peripheral circulation, on the in situ cheek pouch was significantly attenuated in spontaneously hypertensive hamsters relative to age- and genetically matched normotensive hamsters (P < 0.05). However, nitroglycerin-induced vasodilation was similar in both groups. Pretreatment with SQ-29548, a selective and potent PGH(2)-TxA(2)-receptor antagonist, restored acetylcholine- and VIP-induced vasodilation in spontaneously hypertensive hamsters. SQ-29548 had no significant effects on resting arteriolar diameter and on nitroglycerin-induced vasodilation in both groups. SQ-29548 slightly but significantly potentiated VIP- but not acetylcholine-induced vasodilation in normotensive hamsters. Collectively, these data indicate that activation of PGH(2)-TxA(2) receptors impedes agonist-induced vasodilation in the in situ cheek pouch of spontaneously hypertensive hamsters. We suggest that this model is suitable for studying the role of prostanoids in mediating vasomotor dysfunction observed in genetic hypertension.     

Agonist-induced release of nitric oxide during acute exposure to nicotine

While we have shown that acute infusion of nicotine impairs agonist-induced dilatation of resistance arterioles (Am. J. Physiol. 272:H2337-H2342, 1997), no studies have examined the release of nitric oxide in response to these agonists before and during treatment with nicotine. Thus, the first goal of the present study was to examine agonist-induced release of nitric oxide by the hamster cheek pouch microcirculation under control conditions and during acute infusion of nicotine. We measured the release of nitric oxide (Sievers NO analyzer) in response to repeated topical application of acetylcholine (1.0 microM) and 5'-adenosine diphosphate (ADP; 1.0 microM) during infusion of vehicle and during infusion of nicotine (2.0 microg/kg/min i.v. for 30 minutes followed by a maintenance dose of 0.35 microg/kg/min). In hamsters treated with vehicle, topical application of acetylcholine and ADP elicited reproducible increases in nitric oxide release. In contrast, in hamsters treated with nicotine, there was a marked inhibition of nitric oxide release in response to acetylcholine and ADP. In a previous study (J. Appl. Physiol. 85:1292-1298, 1998) we found that treatment of the hamster cheek pouch microcirculation with superoxide dismutase restored impaired agonist-induced vasodilatation during acute infusion of nicotine. Thus, our second goal was to examine whether superoxide dismutase would restore agonist-induced release of nitric oxide during infusion of nicotine. We found that treatment of the hamster cheek pouch microcirculation with superoxide dismutase prior to infusion of nicotine prevented nicotine-induced impairment of nitric oxide release in response to acetylcholine and ADP. We suggest that nicotine alters dilatation of arterioles via an increased release of superoxide anion and subsequent inactivation of nitric oxide.     

Hog barn dust extract stimulates IL-8 and IL-6 release in human bronchial epithelial cells via PKC activation.

Hog barn workers have an increased incidence of respiratory tract symptoms and demonstrate an increase in lung inflammatory mediators, including interleukin (IL)-8 and IL-6. Utilizing direct kinase assays for protein kinase C (PKC) activation, we demonstrated that dust from hog confinement facilities, or hog dust extract (HDE), augments PKC activity of human airway epithelial cells in vitro. A 5% dilution of HDE typically stimulates an approximately twofold increase in human bronchial epithelial cell (HBEC) PKC activity compared with control medium-treated cells. This increase in PKC is observed with 15 min of HDE treatment, and kinase activity reaches peak activity by 1-2 h of HDE treatment before returning to baseline PKC levels between 6 and 24 h. The classic PKC inhibitor, calphostin C, blocks HDE-stimulated PKC activity and associated IL-8 and IL-6 release. Desensitization to HDE stimulation of PKC activation does not appear to occur because subsequent exposures to HDE after an initial exposure result in further augmentation of PKC. Detoxification of HDE with polymyxin B to remove endotoxin did not change PKC activation or IL-8 release, suggesting that endotoxin is not solely responsible for HDE augmentation of PKC. These data support the hypothesis that HDE exposure augments HBEC IL-8 and IL-6 release via a PKC-dependent pathway.     

Inhibition of DNA synthesis in hamster cheek pouch tissue in organ culture by dibutyryl cyclic AMP and a homologous extract

Hamster cheek pouch tissue cultured with 10⁻⁴M dibutyryl cyclic AMP exhibits inhibition of the rate of DNA synthesis. When tissue is cultured with dibutyryl for different time periods throughout the 18 hours of incubation, the effect on the rate of DNA synthesis is very similar. A combination of dibutyryl cyclic AMP and an epithelial cell extract from hamster cheek pouch tissue containing a natural epithelial chalone, appears to have an additive effect on the inhibition of the DNA synthesis rate.