Direct evidence for cross-activation of cGMP-dependent protein kinase by cAMP in pig coronary arteries

Elevation of either cAMP or cGMP causes smooth muscle relaxation. Whether these effects are mediated through cAMP-dependent protein kinase (cAK), cGMP-dependent protein kinase (cGK), or both is unknown. Pig coronary arteries were treated with sodium nitroprusside (SNP) or atrial natriuretic factor (ANF), relaxants which elevate cGMP, and with isoproterenol or forskolin, relaxants which elevate cAMP. Incubation of the arteries with 10 microM SNP produced a 3.3-fold increase in cGMP without altering cAMP; the cGK activity ratio (-cGMP/+cGMP) in these extracts was increased by 2.6-fold as determined by a newly developed assay, while the cAK activity ratio (-cAMP/+cAMP) was unchanged. The increase in cGK activity ratio by SNP was concentration-dependent and was nearly maximal at 30 s. Treatment of the tissue with 10 nM ANF also increased the cGK activity ratio (2.3-fold), but not that of cAK. 100 microM isoproterenol caused a 2.9-fold elevation of cAMP with no change in cGMP, but both cAK and cGK activity ratios were increased (2.3- and 1.6-fold, respectively). The increase in the cGK activity ratio could be mimicked by cAMP addition to control tissue extracts at the concentration measured in extracts of the isoproterenol-treated tissue. Forskolin (1 and 10 microM) also increased the cGK activity ratio (1.9- and 4.9-fold). The increases in cGK activity observed in extracts suggest that moderate elevation of either cGMP or cAMP causes intracellular cGK activation, thus producing relaxation of vascular smooth muscle.

Nonspecific hemolytic effector of activated macrophages as activation marker of allograft rejection

The aim was to assess a nonspecific hemolytic effector of activated monocytes/macrophages, designated spontaneous plaque-forming cell (SPFC), as an activation marker in allograft rejection. An in vitro study on the immunologic characteristics of SPFC monocytes in man and an in vivo study in Lewis rats as to the monitoring of SPFC generation of allograft infiltrating cells with or without immunosuppression were conducted. Hemolysis of SPFC was mediated by CR3 adhesion molecules, detected by Mo-1 and OKM10 monoclonal antibodies. Hemolysis of SPFC was nonspecific, and nonrosette-forming T cells with autologous erythrocytes (non-ARFC-T) acted as suppressor T cells inhibiting SPFC-hemolysis against autologous erythrocytes. A 6-day course of immunosuppression with a daily dose of cyclosporin A (CyA) 10 mg/kg and of FK506 1 mg/kg suppressed the SPFC generation to the level of syngeneic control. In contrast, peak SPFC generation coincided with rejection, and the degree of SPFC generation reflected the grade of histoincompatibility. The present findings suggested that SPFC-activated monocytes/macrophages may be one of the activation markers in allograft rejection and lead to a new concept of graft rejection and self or nonself discrimination mediated by nonspecific, hemolytic SPFC effectors and suppressor T cells inhibiting autoreactivity.

Control of humoral and cellular immunity-mediated accelerated heart allograft rejection in sensitized rats by low dose FK 506 and splenectomy

ACI heart grafts are rejected, at an accelerated pace, in Lewis (LEW) rats sensitized by donor-type blood admixed with immunoadjuvant (adjuvant complete Freund, ACF) 7 days earlier. In an in vitro study, the anti-ACI cytotoxic antibody titers in the serum increased from 1:4 in nonsensitized rats to 1:128 in sensitized rats; the spontaneous blastogenesis in spleen cells was higher in sensitized rats than in nonsensitized rats; spleen cells from sensitized rats showed a strong proliferative response against donor strain stimulator cells compared with the control; the cytotoxic T cell activity of spleen cells from sensitized rats was higher than that of spleen cells from nonsensitized rats. Treatment with low dose FK 506 in combination with splenectomy (Spx) synergistically prolonged the heart allograft survival in this sensitized rat model.

IN CONCLUSION

(1) Both humoral and cellular responses against the donor antigen appear in the serum and in the spleen of rats sensitized by donor-type blood admixed with immunoadjuvant ACF. (2) A low dose of FK 506 together with Spx appears to control this sensitization through different mechanisms, resulting in a prolongation of heart allograft survival.

Cellular mechanisms: induction of heart allograft survival in rats by 15-deoxyspergualin

Survival of ACI rat heart grafts in Lewis rat (LEW) recipients treated with a short course of 15-deoxyspergualin (DSG), in a dose of 5 mg/kg daily beginning from day 4 of grafting, was markedly prolonged, with a mean survival time of 29.8 +/- 3.0 days. On day 20 after grafting, the cellular mechanism of inducing allograft survival after DSG treatment was analyzed by testing the activation of spleen cells in several assay systems. The results indicate that spleen cells from DSG-treated rats with surviving heart allografts show almost no proliferative response against donor strain stimulator cells in the mixed lymphocyte reaction (MLR) as compared with controls. Their cytotoxic activity was lower than that of spleen cells from rats with heart allograft rejection towards donor strain target cells. Adding various concentrations of spleen cells from DSG-treated LEW rats with surviving ACI heart allografts to the MLR when the responder cells from normal LEW rats were exposed to irradiated ACI or Wistar (third party) stimulator cells revealed a strong suppression, in a cell-dose-dependent manner. Moreover, the transfer of 2.0 x 10(8) spleen cells from DSG-treated LEW rats with surviving ACI heart allografts to an irradiated grafted host did not prolong the survival either of the ACI heart grafts or of the third party Wistar heart grafts. These results suggest that the proliferative response and cytotoxic activity are lowered and suppressor cells are induced by treatment with DSG, in rats with surviving allografts.

Bronchial smooth muscle mechanics of a canine model of allergic airway hyperresponsiveness

Although we have reported that tracheal smooth muscle from sensitized dogs shows altered mechanical properties, we did not know, because of technical difficulties with the preparation, whether similar changes occur in the properties of sensitized central bronchial smooth muscle (BSM), the site at which the acute asthmatic response is believed to develop. We have now succeeded in developing a cartilage-free BSM preparation that retains optimal mechanical properties. Such strips were obtained from mongrel dogs that had been sensitized to ragweed pollen. Controls were littermates injected with adjuvant alone. Length-tension relationships were obtained for both control and sensitized BSM strips (CBSM and SBSM, respectively). The maximal active stresses were the same (P greater than 0.05) when normalized to muscle fraction in total tissue cross-sectional area [6.2 +/- 0.6 x 10(4) and 5.9 +/- 0.6 x 10(4) (SE) for SBSM and CBSM, respectively]. This suggests that optimal tension is an insensitive indicator of bronchial hyperresponsiveness and that isotonic studies might be more revealing. The maximal shortening velocity (Vo) for SBSM at 2 s [0.35 +/- 0.017 (SE) lo/s, where lo signifies optimal muscle length], in the course of a 10-s contraction, was significantly greater (P less than 0.05) than Vo measured for CBSM (0.27 +/- 0.015 lo/s). However, Vo did not differ at the 8-s point of contraction. The sensitized group demonstrated a statistically significantly greater maximal shortening capacity (0.67 +/- 0.04 lo) than the control group (0.51 +/- 0.04 lo). At 2 s of contraction, 80% of maximal SBSM shortening had been completed and was significantly greater than for CBSM.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of the antigenic phenotype of human breast carcinoma cells by modifiers of protein kinase C activity and recombinant human interferons

In the present study we have analyzed the effect of a synthetic protein kinase C (PKC) activator 3-(N-acetylamino)-5-(N-decyl-N-methylamino)-benzyl alcohol (ADMB) and the natural PKC-activating tumor-promoting agents 12-O-tetradecanoylphorbol 13-acetate (TPA) and mezerein on the antigenic phenotype of T47D human breast carcinoma cells. All three agents increased the surface expression of the tumor-associated antigen BCA 225 and various cellular antigens, including HLA class II antigens, intercellular adhesion molecule 1 (ICAM-1) and c-erbB-2. Expression of the same antigens was also upregulated to various extents in T47D cells by recombinant fibroblast (IFN beta) and immune (IFN gamma) interferon. Shedding of BCA 225 from T47D cells was induced by TPA, mezerein, IFN beta and IFN gamma, whereas ADMB did not display this activity. The ability of ADMB, TPA and mezerein to modulate the antigenic phenotype of T47D cells appears to involve a PKC-mediated pathway, since the PKC inhibitor, H-7, eliminates antigenic modulation. In contrast, the ability of IFN beta and IFN gamma to enhance the synthesis, expression and shedding of BCA 225, as well as to enhance HLA class II antigens, c-erbB-2 and ICAM-1 expression, was either unchanged or modestly reduced by simultaneous exposure to H-7. Analysis of steady-state mRNA levels for HLA class I antigens, HLA class II-DR beta antigen, ICAM-1 and c-erbB-2 indicated that the ability of H-7 to inhibit expression of these antigens in TPA-, mezerein- and ADMB-treated cells was not a consequence of a reduction in the steady-state levels of mRNAs for these antigens. The results of the present investigation indicate that the biochemical pathways mediating enhanced antigenic expression in T47D cells induced by TPA, mezerein and the synthetic PKC activator ADMB are different from those induced by recombinant interferons. Furthermore, up-regulation of antigenic expression in T47D cells can occur by a PKC-dependent or a PKC-independent pathway.

Potassium permanganate as an in situ probe for B-Z and Z-Z junctions

The availability of DNA structural probes that can be applied to living cells is essential for the analysis of biological functions of unusual DNA structures adopted in vivo. We have developed a chemical probe assay to detect and quantitate left-handed Z-DNA structures in recombinant plasmids in growing E. coli cells. Potassium permanganate selectively reacts with B-Z or Z-Z junction regions in supercoiled plasmids harbored in the cells. Restriction enzyme recognition sites located at these junctions are not cleaved by the corresponding endonuclease after modification with KMnO4. This inhibition of cleavage allows the determination of the relative amounts of B- and Z-forms of the cloned inserts inside the cell. We have successfully applied this method to monitor the extent of Z-DNA formation in E. coli as a function of the growth phase and mutated topoisomerase or gyrase activities. The assay can in principle be used for any unusual DNA structure that contains a restriction recognition site inside or near the structural alteration. It can be a useful tool to analyze in vivo correlations between DNA structure and gene regulatory events.

Defined chemically cross-linked oligomers of human C-reactive protein: characterization and reactivity with the complement system

Chemically cross-linked C-reactive protein (CRP) oligomers were prepared and characterized, and C1q binding and C activation were investigated. Purified human CRP was polymerized in the presence of both non-cleavable and cleavable cross-linking agents and further separated by Superose 12 analytical FPLC column chromatography into fractions of 110 KDa (pentameric monomers), 220 KDa (dimers) and 330 KDa (trimers); virtually no larger oligomers were formed under a variety of experimental conditions. CRP subunits were cross-linked both within and between CRP pentamers. CRP trimers retained native CRP antigenicity without expression of neo-CRP epitopes. CRP trimers showed maximal binding and CRP dimers showed partial binding of solid phase C1q while CRP monomers bound virtually no C1q at all; CRP trimers also bound to fluid phase C1q. Binding was Ca++ independent and increased as the ionic strength or pH were lowered, characteristics comparable to binding of aggregated IgG to C1q; it was not inhibited by phosphorylcholine. CRP trimers consumed total C, C1 and C2 haemolytic activities upon incubation in fresh human serum, but much less efficiently than did CRP-protamine complexes or Agg-IgG. CRP trimers failed to deplete alternative C pathway haemolytic activity at all. The stable, chemically defined CRP oligomers described in this report, which bind C1q efficiently but display poor ability to activate the classical C pathway in the absence of an appropriate ligand, should be valuable in further studies of the interactions between CRP and the C system.

Inhibitory regulation of serum factor(s)-caused ornithine decarboxylase induction by the protein kinase C system in A431 human epidermoid carcinoma cells

Replacement of the culture medium with fresh medium containing 10% fetal calf serum caused ornithine decarboxylase (ODC) induction in A431 human epidermoid carcinoma cells. Two peaks of ODC activity were observed at 5 and 14 hr after the medium replacement. The peak activity observed at 5 hr was more prominent than that at 14 hr. The first peak of ODC induction was suppressed by a potent protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), in a concentration-dependent manner. The second peak, however, was not suppressed by TPA. Other potent protein kinase C activators, such as mezerein and 12-O-retinoylphorbol-13-acetate, also suppressed the first peak of ODC induction. Synthetic diacylglycerols, 1,2-dioctanoyl-sn-glycerol and 1-oleoyl-2-acetylglycerol, did not inhibit the serum factor(s)-caused ODC induction. Phorbol-13-acetate, an inactive phorbol ester, also failed to inhibit the ODC induction. The growth of A431 cells was slightly suppressed by TPA. In protein kinase C down-regulated cells, TPA failed to inhibit the serum factor(s)-caused ODC induction. These results suggest that the serum factor(s)-caused ODC induction in A431 cells is negatively regulated by the protein kinase C system, which may not be activated by exogenous diacylglycerols.

Normalization of force generated by canine airway smooth muscles

A variety of normalizations have been employed to compare maximal isometric force (Po) produced by smooth muscles at different locations and stages of maturation. Because these procedures have not always been based on rigorous principles, confusion has resulted. To obtain a less ambiguous index of force production, we measured in vitro Po from mongrel canine tracheal (TSM) and bronchial (BSM) smooth muscle with an electromagnetic lever and normalized it to force per unit cross-sectional area of whole tissue (tissue stress), to force per unit cross-sectional area of muscle in the cross section of total tissue (muscle stress), and to force per fractional unit of myosin in the tissue cross section (myosin stress). Proportion of myosin in cross-sectional area of tissue was deduced from data obtained by sodium dodecyl sulfate gel electrophoresis of crude muscle extracts. For TSM, tissue stress was 1.499 X 10(5) N/m2 +/- 0.1 (SE), whereas it was only 0.351 X 10(5) N/m2 +/- 0.05 (SE) for BSM, representing a 4.27-fold difference (P less than 0.01). There was a 1.60-fold difference (P less than 0.05) in muscle stress, which was correlated to the morphometric finding that 79 +/- 1.4% (SE) of the tracheal strip cross section was muscle, whereas only 30 +/- 1.0% (SE) of bronchial tissue was occupied by muscle. Average myosin content was the same in smooth muscle cells of TSM and BSM, indicating that total amount of myosin in tissue cross sections was essentially a function of proportional area of muscle cells in total tissue cross sections.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of prostaglandin E2 in the tumor promoter phorbol ester-caused increase in epidermal cholesterol sulfotransferase activity

A single topical application of 10 nmol TPA to mouse skin caused an increase in epidermal cholesterol sulfotransferase activity, a squamous differentiation associated enzyme. A topical application of indomethacin (1.2 mumol), a cyclooxygenase inhibitor, 10 min before TPA application markedly inhibited the above TPA action. Concurrent application of prostaglandin E2 (PGE2) with indomethacin reversed the inhibitory effect of indomethacin. PGF2 alpha, however, failed to reverse the inhibition caused by indomethacin. Both indomethacin and PGE2 alone did not change epidermal cholesterol sulfotransferase activity significantly. These results indicate that PGE2 plays a significant role in the mechanism of TPA-caused increase in cholesterol sulfotransferase activity in mouse epidermis.

Survival of cardiac allograft in highly sensitized and nonsensitized rats treated with FK506

The effect of FK506 was studied in sensitized and nonsensitized recipients using a rat cardiac allograft model. Heart grafts from Male ACI rats were heterotopically transplanted to Male LEW rats. The sensitized rat models were established by using donor type blood, admixed with immunoadjuvant (Adjuvant Complete Freund), seven days prior to transplantation. FK506 was administrated from day 0 to day 14 posttransplantation. The results showed that FK506 could prolong allograft survival in both sensitized and nonsensitized rat recipients in a dose-dependent manner, although, the dose required in sensitized recipients was higher than in nonsensitized recipients. The minimal effective dose of FK506 was 0.32 mg/kg/day in sensitized recipients and 0.1 mg/kg/day in nonsensitized recipients.