Sequential use of Prepidil and extra-amniotic saline infusion for the induction of labor in nulliparous women with very low Bishop scores

OBJECTIVE

To evaluate the efficacy of sequential use of Prepidil (prostaglandin E2 gel) and extra-amniotic saline infusion for the induction of labor in nulliparous women with very low Bishop scores.

STUDY DESIGN

Nulliparous women with singleton gestations, intact membranes and a cervical Bishop score of < or = 2 who received Prepidil gel and extra-amniotic saline infusion sequentially for the induction of labor between July 1996 and July 1998 were studied.

RESULTS

Thirty-one women met the inclusion criteria. Indications for induction included post-dates (six of 31), pre-eclampsia (ten of 31), diabetes (three of 31), oligohydramnios (three of 31), intrauterine growth restriction (two of 31) and non-reactive non-stress test (NST) (seven of 31). The average time from onset of induction to delivery was 38.1 +/- 13.5 h. Vaginal delivery was achieved in 80.6%. Women requiring > 2 doses of Prepidil had a higher risk of delivering abdominally (OR = 3.5). Three of seven (42.9%) women with labor induced for non-reactive NST but only three of 24 (12.5%) with labor induced for other indications had a Cesarean section delivery (p < 0.001).

CONCLUSIONS

Nulliparous women with very unfavorable cervices can be counselled that they have an 80% chance of vaginal delivery using sequential Prepidil and extra-amniotic saline infusion as an induction method, with 90% delivering within the first 48 h.

Nuclear gems and Cajal (coiled) bodies in fetal tissues: nucleolar distribution of the spinal muscular atrophy protein, SMN

SMN, the affected protein in spinal muscular atrophy (SMA), is a cytoplasmic protein that also occurs in nuclear structures called "gems" and is involved in snRNP maturation. Coilin-p80 is a marker protein for nuclear Cajal bodies (coiled bodies; CBs) which are also involved in snRNP maturation, storage or transport. We now show that gems and CBs are present in all fetal tissues, even those that lack gems/CBs in the adult. Most gems and CBs occur as separate nuclear structures in fetal tissues, but their colocalization increases with fetal age and is almost complete in the adult. In adult tissues, up to half of all gems/CBs are inside the nucleolus, whereas in cultured cells they are almost exclusively nucleoplasmic. The nucleolar SMN is often more diffusely distributed, compared with nucleoplasmic gems. Up to 30% of cells in fetal tissues have SMN distributed throughout the nucleolus, instead of forming gems in the nucleoplasm. The results suggest a function for gems distinct from Cajal bodies in fetal nuclei and a nucleolar function for SMN. Spinal cord, the affected tissue in SMA, behaves differently in several respects. In both fetal and adult motor neurons, many gems/CBs occur as larger bodies closely associated with the nucleolar perimeter. Uniquely in motor neurons, gems/CBs are more numerous in adult than in fetal stages and colocalization of gems and CBs occurs earlier in development. These unusual features of motor neurons may relate to their special sensitivity to reduced SMN levels in SMA patients.

In vitro comparison of peak polymerization temperatures of 5 provisional restoration resins

BACKGROUND

The heat produced by provisional restoration materials may injure the dental pulp. This study measured and compared peak temperatures during polymerization of 5 materials used in the fabrication of provisional restorations.

METHODS

The tested materials were 2 self-curing resins (Integrity and Protemp) and 3 dual-cure resins (Iso-Temp, TCB Dual Cure and Provipont DC). A mould the size of a maxillary molar tooth was fabricated to contain 0.5 cc of resin. The temperature rise of the different materials was recorded every 10 seconds over a 10-minute period.

RESULTS

The rise in temperature of Integrity (peak temperature of 33.8 degrees C) and Protemp Garant (35.6 degrees C) was significantly higher than the rise in temperature of Iso-Temp (29.5 degrees C), TCB Dual Cure (28.4 degrees C) and Provipont DC (29.5 degrees C).

CONCLUSION

Use of the dual-cure resins in provisional restorations may reduce the risk of pulp injury.

Synthesis and in vitro opioid activity profiles of DALDA analogues

The tetrapeptide DALDA (H-Tyr-D-Arg-Phe-Lys-NH2) is a polar and selective mu agonist showing poor penetration of the placental and blood-brain barriers. In an effort to enhance the potency of DALDA, analogues containing 2',6'-dimethyltyrosine (Dmt), N,2',6'-trimethyltyrosine (Tmt), 2'-methyltyrosine (Mmt) or 2'-hydroxy,6'-methyltyrosine (Hmt) in place of Tyr1, or Orn or alpha,gamma-diaminobutyric acid (A2bu) in place of Lys4, were synthesized. All compounds displayed high mu receptor selectivity in the rat and guinea pig brain membrane binding assays and most of them were more potent mu agonists than DALDA in the mu receptor-representative guinea pig ileum assay, with [Dmt1]DALDA showing the highest potency. Because of its extraordinary mu agonist potency, high mu selectivity, polar character (charge of 3 + ) and metabolic stability, [Dmt1]DALDA has potential for use in obstetrical or peripheral analgesia.

Expectant management of severe preterm preeclampsia: is intrauterine growth restriction an indication for immediate delivery?

OBJECTIVE

Expectant management of severe preterm preeclampsia is gaining widespread acceptance in clinical practice. The objective of our study was 2-fold-to determine the frequency of fetal deterioration with expectant management of severe preterm preeclampsia and to evaluate whether the presence of intrauterine growth restriction on admission is associated with a shorter admission-to-delivery interval or more deliveries resulting from nonreassuring fetal status in comparison with pregnancies with preeclampsia but without intrauterine growth restriction.

STUDY DESIGN

This was an observational study of women with singleton pregnancies at <34 completed weeks' gestation who were admitted to the hospital with the diagnosis of severe preeclampsia and managed expectantly. Fetal status on admission, admission-to-delivery interval, indication for delivery, and neonatal outcome were examined.

RESULTS

Forty-seven women were studied during a 3-year period (1996-1999). Gestational age at admission was 29.8 +/- 2.6 weeks. The mean admission-to-delivery interval for the entire group was 6.0 +/- 5.1 days; in 42.5% delivery was for fetal indications. In comparison with the absence of intrauterine growth restriction, the presence of intrauterine growth restriction at admission resulted in a significantly shorter admission-to-delivery interval (3.1 +/- 2.1 vs 6.6 +/- 6.1 days; P <.05). Most fetuses with intrauterine growth restriction (85.7%) were delivered before 1 week. Although 57% of fetuses with intrauterine growth restriction were delivered for fetal indications, versus 39% of fetuses without intrauterine growth restriction, these rates were not found to be significantly different. Neonatal outcomes, as reflected by Apgar scores, number of admissions to and duration of stay in the neonatal intensive care unit, and neonatal mortality rates, were similar.

CONCLUSION

Pregnancies complicated by severe preterm preeclampsia and the presence of intrauterine growth restriction at admission may not benefit from expectant management beyond the 48 hours needed for betamethasone to act. Furthermore, all patients may benefit from close fetal monitoring before delivery because of the high rate of intervention for deteriorating fetal status.

Digital overlay technique for documenting toric intraocular lens axis orientation

PURPOSE

To describe a digital overlay technique for documenting toric intraocular lens (IOL) axis alignment.

SETTING

Jules Stein Eye Institute and the Department of Ophthalmology, University of California at Los Angeles School of Medicine, Los Angeles, California, USA.

METHODS

Digital overlay imaging was used to evaluate the alignment of Staar toric IOLs in 4 eyes of 3 patients who had regular corneal astigmatism at the time of cataract surgery. Lens axes were determined by computerized analysis of digitally scanned retroillumination photographs. A stock digital image of a Staar AA4203TF toric IOL was superimposed on corneal topography images to document IOL alignment with the steep corneal meridian.

RESULTS

Digital overlay images demonstrated that 3 IOLs in the sample group were within 5 degrees and 1 was within 20 degrees of the intended axis at the time of the final postoperative examination. Slitlamp lens axis estimations were 3 to 18 degrees different from that determined by this technique.

CONCLUSION

Digital overlay imaging of correctly oriented toric IOLs on computerized corneal topography maps represents an intuitive, accurate, and visually appealing method of documenting toric IOL axis alignment.

Characterization of a monoclonal antibody panel shows that the myotonic dystrophy protein kinase, DMPK, is expressed almost exclusively in muscle and heart

Myotonic dystrophy (DM) is a multisystemic disorder caused by an inherited CTG repeat expansion which affects three genes encoding the DM protein kinase (DMPK), a homeobox protein Six5 and a protein containing WD repeats. Using a panel of 16 monoclonal antibodies against several different DMPK epitopes we detected DMPK, as a single protein of approximately 80 kDa, only in skeletal muscle, cardiac muscle and, to a lesser extent, smooth muscle. Many earlier reports of DMPK with different sizes and tissue distributions appear to be due to antibody cross-reactions with more abundant proteins. One such antibody, MANDM1, was used to isolate two related protein kinases, MRCK alpha and beta, from a human brain cDNA library and the shared epitope was located at the catalytic site of DMPK using a phage-displayed random peptide library. The peptide library also identified an epitope shared between DMPK and a 55 kDa muscle-specific protein. The results suggest that effects of the repeat expansion on the DMPK gene may be responsible for muscle and heart features of DM, whereas clinical changes in other tissues may be due to effects on the other two genes.

The TIPP opioid peptide family: development of delta antagonists, delta agonists, and mixed mu agonist/delta antagonists

The discovery of the prototype delta opioid antagonists TIPP (H-Tyr-Tic-Phe-Phe-OH) and TIP (H-Tyr-Tic-Phe-OH) in 1992 was followed by extensive structure-activity relationship studies, leading to the development of analogues that are of interest as pharmacological tools or as potential therapeutic agents. Stable TIPP-derived delta opioid antagonists with subnanomolar delta receptor binding affinity and extraordinary delta receptor selectivity include TIPP[Psi] (H-Tyr-TicPsi[CH(2)NH]Phe-Phe-OH] and TICP[Psi] (H-Tyr-TicPsi[CH(2)NH]Cha-Phe-OH); Cha: cyclohexylalanine), which are widely used in opioid research. Theoretical conformational analyses in conjunction with the pharmacological characterization of conformationally constrained TIPP analogues led to a definitive model of the receptor-bound conformation of H-Tyr-Tic-(Phe-Phe)-OH-related delta opioid antagonists, which is characterized by all-trans peptide bonds. Further structure-activity studies revealed that the delta antagonist vs delta agonist behavior of TIP(P)-derived compounds depended on very subtle structural differences in diverse locations of the molecule and suggested a delta receptor model involving a number of different inactive receptor conformations. A further outcome of these studies was the identification of a new class of potent and very selective dipeptide delta agonists of the general formula H-Tyr-Tic-NH-X (X = arylalkyl), which are of interest for drug development because of their low molecular weight and lipophilic character. Most interestingly, TIPP analogues containing a C-terminal carboxamide group displayed a mixed mu agonist/delta antagonist profile, and thus were expected to be analgesics with a low propensity to produce tolerance and physical dependence. This turned out to be the case with the TIPP-derived mu agonist/delta antagonist DIPP-NH(2)[Psi] (H-Dmt-TicPsi[CH(2)NH]Phe-Phe-NH(2)); Dmt: 2',6'- dimethyltyrosine).

Matrix-assisted laser desorption/ionization mass spectrometric quantification of the mu opioid receptor agonist DAMGO in ovine plasma

The synthetic opioid peptide analog Tyr-D-Ala-Gly-N-methyl-Phe-Gly-ol (DAMGO), which is a mu opioid receptor-selective agonist, was quantified in ovine plasma samples with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), using delayed extraction and a reflectron. The internal standard was pentadeuterated DAMGO. Timed-ion selection was used to select the precursor ion. The analysis of the post-source decay fragments improved the detection sensitivity, and the use of the precursor-product ion relationship optimized the specificity. For plasma samples, the inter-assay variability of this method was 6.4% (n = 79) and the intra-assay variability was 6.0% (n = 10). The variability for controls was 3.4% (n = 43). The profile of DAMGO amount versus time was determined in sheep plasma, and the corresponding pharmacokinetic data were calculated.

Squash trypsin inhibitors from Momordica cochinchinensis exhibit an atypical macrocyclic structure

Three trypsin inhibitors (TIs), from the seeds of the squash Momordica cochinchinensis (MCo), have been isolated and purified using gel filtration, ion exchange chromatography, and reverse-phase HPLC. Their sequences could be determined only after proteolytic cleavages. In the case of MCoTI-I and -II, it was shown that their polypeptide backbones are cyclic, a structure that has never been described in squash TIs. They contain 34 amino acid residues with 3 disulfide bridges and measured molecular masses of 3453.0 and 3480.7, respectively. They are the largest known macrocyclic peptides containing disulfide bridges. Their sequences show strong homology to other squash TIs, suggesting a similar three-dimensional structure and an analogous mechanism of action. A model of MCoTI-II was constructed by analogy to the crystal structure of the complex between bovine trypsin and CMTI-I, indicating that the linker connecting the two termini is flexible and does not impose significant geometrical constraints. This flexibility allows an Asp-Gly peptide bond rearrangement to occur in this region, giving rise to two isoforms of MCoTI-II. Although the importance of cyclization is not clear, it might confer increased stability and resistance to proteolysis. A minor species, MCoTI-III, was also characterized as containing 30 amino acid residues with a molecular mass of 3379.6. This component possesses a linear backbone with a blocked N-terminus. MCoTIs represent interesting candidates for drug design, either by changing their specificity of inhibition or by using their structure as natural scaffolds bearing new binding activities.

Imaging the sphenoid sinus: pictorial essay

This paper focuses on the spectrum of sphenoid sinus lesions that may be seen radiologically and the mapping of disease extent. Imaging plays a central role in the assessment of sphenoid sinus disease. Although primary sphenoid sinus disease is uncommon, this sinus is nevertheless affected secondarily by a variety of pathological processes.

Characteristics of repeat aborters in Vietnam

Two hundred and sixty married women seeking induced abortion service in Hanoi, Vietnam were interviewed to determine the magnitude of repeat induced abortion and explore selected characteristics of the repeat aborters. Seventy-one percent of the sample reported having had at least one previous induced abortion. After adjustment for age and number of living children, poor attitudes toward contraception, low use of modern contraceptives and failure of contraception were shown to be significantly associated with repeat induced abortion. Woman's age, number of living children, contraceptive knowledge and experience and desire for no more children were positively related to repeat induced abortion. Socio-demographic characteristics were not related to repeat induced abortion. Improvement of attitudes toward contraception, persuasion to use modern contraception and promotion of contraceptive effectiveness are recommended strategies to prevent repeat induced abortion.

Novel ligands lacking a positive charge for the delta- and mu-opioid receptors

Recently we reported using minilibraries to replace Lys(9) [somatostatin (SRIF) numbering] of the potent somatostatin agonist L-363,301 (c[-Pro-Phe-D-Trp-Lys-Thr-Phe-]) to generate the potent neurokinin receptor (NK-1) antagonist c[-Pro-Phe-D-Trp-p-F-Phe-Thr-Phe-]. This novel cyclic hexapeptide did not bind the SRIF receptor. Thus, a single mutation converted L-363,301, a SRIF agonist with potency ca. 2-8 times the potency of SRIF in laboratory animals,(24) into a selective NK-1 receptor antagonist with an IC(50) of 2 nM in vitro. During the screening of the same libraries for ligands of the delta-opioid receptor, we identified four compounds (1-4) which represent a new class of delta-opioid antagonists, some of which were also NK-1 receptor antagonists. The most potent delta-opioid antagonist, c[-Pro-1-Nal-D-Trp-Tyr-Thr-Phe-] (2), showed a K(e) value of 128 nM in the mouse vas deferens assay and a delta-receptor binding affinity constant of 152 nM in the rat brain membrane binding assay. These results are of interest because they represent a novel class of delta-opioid antagonists and, like two previously reported delta-opioid antagonists, they lack a positive charge. To examine further the requirement for a positive charge in the delta-opioid ligands, we prepared two analogues of the beta-casomorphin-derived mixed mu-agonist/delta-antagonist, H-Dmt-c[-D-Orn-2-Nal-D-Pro-Gly-] (7), in which we eliminated the positive charge either through formylation of the primary amino group (5) or by the deletion of this N-terminal amino group (6). These latter compounds proved to be delta-opioid antagonists with K(e) values in the 16-120 nM range, as well as fairly potent mu-opioid antagonists (K(e) approximately 200 nM). These six compounds provide the most convincing evidence to date that there is no requirement for a positive charge in mu- and delta-opioid receptor antagonists. In addition, cyclic hexapeptide 4 lacks a phenolic hydroxyl group. Taken together, these data suggest that the prevailing assumptions about delta- and mu-opioid receptor binding need revision and that the receptors for these opioid ligands have much in common with the NK-1 and somatostatin receptors.

Sorbitol compared with xylitol in prevention of dental caries

OBJECTIVE

To summarize published data on the comparative efficacy of sorbitol and xylitol for prevention of dental caries.

DATA SOURCES

Published double-blind comparative trials, using sorbitol and xylitol products, identified by MEDLINE (January 1966-December 1998) and International Pharmaceutical Abstracts (January 1970-December 1998) searches.

DATA SYNTHESIS

Clinical trials generally used sorbitol and xylitol gums, which patients chewed three to five times daily for 20-40 months. Xylitol was superior to sorbitol in two longer, secondary dentition trials (30-63% reductions), but not in two primary dentition trials.

CONCLUSIONS

The data suggest that xylitol-containing gums may provide superior efficacy in reducing caries rates in high-risk populations.

The opioid mu agonist/delta antagonist DIPP-NH(2)[Psi] produces a potent analgesic effect, no physical dependence, and less tolerance than morphine in rats

Opioid compounds with mixed mu agonist/delta antagonist properties are expected to be analgesics with low propensity to produce tolerance and dependence. In an effort to strengthen the mu agonist component of the mixed mu agonist/delta antagonist H-Tyr-Tic-Phe-Phe-NH(2) (TIPP-NH(2)), analogues containing structurally modified tyrosine residues in place of Tyr(1) were synthesized. Among the prepared compounds, H-Dmt-Tic-Phe-Phe-NH(2) (DIPP-NH(2); Dmt = 2',6'-dimethyltyrosine) and H-Dmt-TicPsi[CH(2)NH]Phe-Phe-NH(2) (DIPP-NH(2)[Psi]) retained a mixed mu agonist/delta antagonist profile, as determined in the guinea pig ileum and mouse vas deferens assays, whereas H-Tmt-Tic-Phe-Phe-NH(2) (Tmt = N,2',6'-trimethyltyrosine) was a partial mu agonist/delta antagonist and H-Tmt-TicPsi[CH(2)NH]Phe-Phe-NH(2) was a mu antagonist/delta antagonist. DIPP-NH(2)[Psi] showed binding affinities in the subnanomolar range for both mu and delta receptors in the rat brain membrane binding assays, thus representing the first example of a balanced mu agonist/delta antagonist with high potency. In the rat tail flick test, DIPP-NH(2)[Psi] given icv produced a potent analgesic effect (ED(50) = 0.04 microg), being about 3 times more potent than morphine (ED(50) = 0.11 microg). It produced less acute tolerance than morphine but still a certain level of chronic tolerance. Unlike morphine, DIPP-NH(2)[Psi] produced no physical dependence whatsoever upon chronic administration at high doses (up to 4.5 microg/h) over a 7-day period. In conclusion, DIPP-NH(2)[Psi] fulfills to a large extent the expectations based on the mixed mu agonist/delta antagonist concept with regard to analgesic activity and the development of tolerance and dependence.

[Prevention of vitamin D deficiency in the child and adolescent. I. Proposal and arguments for use of a decision tree]

A decision-making table, using three questionnaires, is proposed to determine the vitamin D status in children and adolescents. The first questionnaire assesses the vitamin D endogenous synthesis, taking into account the sunlight exposure and the time interval out of the sun. The second questionnaire quantifies the vitamin D dietary intake within three levels: optimal, medium or low. In case of a medium dietary score, a third questionnaire evaluates the daily calcium intake, taking into account the fact that vitamin D metabolism is increased by a low calcium intake (under 400 mg/day). This decision-making table should enable the detection of children and adolescents at risk of vitamin D deficiency and requiring an adapted prophylaxis. Its accuracy will be assessed in prospective surveys.

Localization of rabbit huntingtin using a new panel of monoclonal antibodies

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG repeat which is expressed as a polyglutamine tract near the N-terminus of the gene product, huntingtin. N-terminal huntingtin fragments form intranuclear aggregates in HD patients and these may be involved in the pathogenesis. Monoclonal antibodies (mAbs) against three different regions of huntingtin (amino acids 997-1276, 1844-2131 and 2703-2911) have been produced and two of the epitopes have been identified using phage displayed peptide libraries. All mAbs reacted with 350 kDa huntingtin on Western blots and one mAb from each region was selected for further study by strong immunoreactivity with neurons in different regions of rabbit brain and by ability to immunoprecipitate native huntingtin. Subcellular fractionation and sucrose density centrifugation of rabbit brain extract showed that most of the huntingtin exists as a high molecular weight complex in the cytoplasm. Two outstanding problems have been addressed; the location of huntingtin in tissues outside the central nervous system and whether huntingtin is present in the nucleus of normal cells. We conclude that huntingtin is present at low levels in most non-neuronal cells though we have identified an interstitial cell type in skin with very high immunoreactivity. Using both immunolocalization and nuclear purification methods, we were unable to exclude the possibility that a small proportion of full-length huntingtin is present in the nucleus.

Ankle sprains and other soft tissue injuries

Lateral ankle sprains are the most frequently encountered injuries in sports. In the evaluation of lateral ankle injury, one should consider all soft tissue structures (i.e., peroneal tendons, ligaments of the ankle, subtalar joints, around the lateral ankle). The treatment of most ankle sprains has evolved from immobilization to functional rehabilitation. Many patients with ankle sprains return to their previous activities. A few patients are left with pain and residual instability after conservative treatment; thus, the question of when to operate on acute severe ankle sprain remains controversial. The other challenge physicians face is the problem of persistent lateral ankle pain after sprain. This condition may be due to intra-articular or extra-articular pathology (i.e., soft tissue lateral ankle impingement, osteochondral lesion, or partial peroneal tendon tear). Diagnosis can be made with careful history, physical examination, and appropriate ancillary studies. Only proper diagnosis can lead to uncompromised, undelayed patient care.

Subtleties of structure-agonist versus antagonist relationships of opioid peptides and peptidomimetics

The development of novel delta opioid antagonists and delta opioid agonists structurally derived from the prototype delta antagonist TIPP (H-Tyr-Tic-Phe-Phe-OH), is reviewed. Both delta antagonists and delta agonists with extraordinary potency and unprecedented delta receptor selectivity were discovered. Some of them are already widely used as pharmacological tools and are also of interest as potential therapeutic agents for use in analgesia. The results of the performed structure-activity studies revealed that the delta antagonist versus delta agonist behavior of this class of compounds depended on very subtle structural differences in diverse locations of the molecule. These observations can be best explained with a receptor model involving a number of different inactive and active receptor conformations.

Disruption of the utrophin-actin interaction by monoclonal antibodies and prediction of an actin-binding surface of utrophin

Monoclonal antibody (mAb) binding sites in the N-terminal actin-binding domain of utrophin have been identified using phage-displayed peptide libraries, and the mAbs have been used to probe functional regions of utrophin involved in actin binding. mAbs were characterized for their ability to interact with the utrophin actin-binding domain and to affect actin binding to utrophin in sedimentation assays. One of these antibodies was able to inhibit utrophin-F-actin binding and was shown to recognize a predicted helical region at residues 13-22 of utrophin, close to a previously predicted actin-binding site. Two other mAbs which did not affect actin binding recognized predicted loops in the second calponin homology domain of the utrophin actin-binding domain. Using the known three-dimensional structure of the homologous actin-binding domain of fimbrin, these results have enabled us to determine the likely orientation of the utrophin actin-binding domain with respect to the actin filament.

Colocalization of emerin and lamins in interphase nuclei and changes during mitosis

Emerin is a nuclear membrane protein which is affected by mutation in X-linked Emery-Dreifuss muscular dystrophy. We have previously suggested that emerin is a member of a family of type II integral membrane proteins which associate with the nuclear lamina and which include lamina-associated proteins and the lamin B receptor. We now show that emerin in COS cells is not restricted to the nuclear rim but is also found at intranuclear sites, where it colocalizes with nuclear lamins B1, B2 and A/C. During mitosis, emerin is dispersed throughout the cell and then participates in the reconstitution of membranes around the daughter nuclei. Although emerin and lamins do not remain colocalized during mitosis, they all show some association with the midbody of the mitotic spindle.

Activation of the epidermal platelet-activating factor receptor results in cytokine and cyclooxygenase-2 biosynthesis

Recent studies suggest that the lipid mediator platelet-activating factor (PAF) is involved in keratinocyte function and skin inflammation. Indeed, PAF is found in association with inflammatory skin diseases, intradermal injections of PAF induce inflammation, and keratinocytes express functional PAF receptors (PAF-R). One mechanism by which the keratinocyte PAF-R could contribute to epidermal functions and inflammatory states would be through the synthesis of inflammatory regulators, such as PAF, PGs, and cytokines. The ability of the epidermal PAF-R to induce the synthesis of these immunomodulators was tested using a model system created by transduction of the PAF-R-negative human epidermal cell line KB with the PAF-R. Activation of this epidermal PAF-R resulted in arachidonic acid release, and the biosynthesis of PAF and PGE2. In addition, the KB PAF-R triggered increased levels of mRNA and protein for the inducible isozyme of cyclooxygenase (COX-2) as well as IL-6 and IL-8, both of which have been implicated in skin inflammatory processes. Studies with the human keratinocyte-derived epidermal cell line HaCaT revealed that activation of the endogenous PAF-R led to the increased accumulation of COX-2, IL-6, and IL-8 mRNA similar to that seen with the KB PAF-R model system. Finally, treatment of HaCaT keratinocytes with IL-8 resulted in PAF biosynthesis, indicating the existence of a positive feedback loop between IL-8 and PAF in epidermal cells. These studies suggest involvement of PAF and the PAF-R in the epidermal cytokine network.