Therapeutic Response to Treatment of a Papillomatous Ocular Surface Squamous Neoplasia With Intramuscular Human Papillomavirus Vaccine

PURPOSE

The purpose of this study was to describe the response of a papillomatous ocular surface squamous neoplasia (OSSN) to the intramuscular (IM) 9-valent human papillomavirus (HPV) vaccine after failed medical and surgical interventions.

METHODS

A 79-year-old White man with a conjunctival lesion underwent a biopsy which revealed OSSN and positivity for high-risk HPV. Initially treated with medical therapy and surgical excisions, the patient developed a recurrence and refused further surgery. He was given 4 doses of IM HPV vaccine at the 6-week interval.

RESULTS

A dramatic reduction in lesion size and reduced epithelial thickening and hyperreflectivity was noted on slitlamp examination and high-resolution anterior segment optical coherence tomography after receiving the IM HPV vaccine. Although lesion size was markedly reduced, the therapy did not achieve total resolution, resulting in further treatment with topical 1% 5-fluorouracil (5-FU) eye drops and later 0.04% mitomycin C eye drops. The patient then elected to discontinue further treatment and solely observe.

CONCLUSIONS

This case report adds to the growing literature demonstrating the potential therapeutic use of vaccines in cancer treatment. Although HPV vaccination is currently approved for prophylaxis, the use of HPV vaccines as a therapeutic option for various HPV-mediated diseases, including OSSN, should be further explored. The HPV vaccine yielded significant initial improvement in this patient who refused further surgical interventions. The use of IM HPV vaccine as an adjunctive treatment of papillomatous OSSN may represent a potential therapeutic option in cases refractory to standard treatment modalities.

A Non-Surgical and Cost-Effective Treatment Approach Employing Topical Imiquimod, 5-Fluorouracil, and Tretinoin for Primary Non-Melanoma Skin Cancers

BACKGROUND

Minimally invasive alternative approaches to treat non-melanoma skin cancers remain limited and unproven.

OBJECTIVE

We aim to assess the efficacy of varying combinations of anti-tumor agents—imiquimod 5% cream, 5-fluorouracil 2% solution, and tretinoin 0.1% cream—with brief cryotherapy in treating non-melanoma skin cancers.

METHODS

This retrospective study included 690 cases of non-melanoma skin cancers in 480 patients who received a diagnosis of a basal cell carcinoma or squamous cell carcinoma during a ten-year period. During treatment period, patients applied 30 applications of one of three combinations (imiquimod/tretinoin, 5-fluorouracil/tretinoin, or imiquimod/5-fluorouracil/tretinoin) and had cryotherapy every 2 weeks. Each patient had a clinical examination at least three years post-treatment or documented treatment failure. Clearance was defined by a lack of persistence or recurrence for 3 years following the completion of treatment. The likelihood of lesion clearance was evaluated using multivariable logistic regression analysis.

RESULTS

A total of 186 cases (97; basal cell carcinoma and 89; squamous cell carcinoma) in 133 patients [37% women and 63% men; median (interquartile range) age, 77 (69, 83) years] met the inclusion criteria. Multivariable logistic regression analysis adjusting for clinical and lesion variables demonstrated that, relative to the imiquimod/5-fluorouracil/tretinoin treatment approach, imiquimod/ tretinoin (odds ratio, 0.05; 95% confidence interval, 0.00-0.99) and 5-fluorouracil/tretinoin (0.02; 0.00–0.45) were associated with lower likelihoods of lesion clearance. Likewise, morpheaform basal cell carcinoma had a lower probability of clearance (0.05; 0.00–0.72).

CONCLUSIONS

The combination of imiquimod/5-fluorouracil/tretinoin with cryotherapy had high clearance rates and was the most effective treatment regimen. J Drugs Dermatol. 2021;20(3):260-267. doi:10.36849/JDD.5427.

Treating Melanoma in Situ During a Pandemic with Telemedicine and a Combination of Imiquimod, 5-Fluorouracil, and Tretinoin

The recent coronavirus disease 2019 (COVID-19) pandemic has created a quandary for the physician in terms of evaluating and treating cutaneous skin cancers, particularly melanomas. At the onset of the pandemic, many planned medical and surgical visits for skin cancers were postponed. Physicians and patients have had to balance the risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with that of worsening morbidity and mortality due to delays in skin cancer treatments. We present a male patient who had two melanoma-in-situs (MISs) that were treated during the COVID-19 pandemic with a combination of topical imiquimod 5% cream, 5-fluorouracil 2% solution, and tretinoin 0.1% cream. The successful treatments occurred without in-person visits and with the aid of telemedicine. Although surgery is the standard for the treatment of melanoma in situ, this case demonstrates an effective viable treatment modality for MIS during a pandemic situation.

Complementary and Alternative Medicine Therapies for Psoriasis: A Systematic Review

Importance

Up to 51% of patients with psoriasis report the use of complementary and alternative medicine (CAM) in their treatment regimen, although it is unclear which CAM therapies are effective for treatment of psoriasis.

Objective

This review compiles the evidence on the efficacy of the most studied CAM modalities for treatment of patients with plaque psoriasis and discusses those therapies with the most robust available evidence.

Evidence Review

PubMed, Embase, and ClinicalTrials.gov searches (1950-2017) were used to identify all documented CAM psoriasis interventions in the literature. The criteria were further refined to focus on those treatments identified in the first step that had the highest level of evidence for plaque psoriasis with more than 1 randomized clinical trial supporting their use. This excluded therapies lacking randomized clinical trial (RCT) data or showing consistent inefficacy.

Findings

Primary CAM therapy searches identified 457 articles, of which 107 articles were retrieved for closer examination. Of those articles, 54 were excluded because the CAM therapy did not have more than 1 RCT on the subject or showed consistent lack of efficacy. An additional 7 articles were found using references of the included studies, resulting in a total of 44 RCTs (17 double-blind, 13 single-blind, and 14 nonblind), 10 uncontrolled trials, 2 open-label nonrandomized controlled trials, 1 prospective controlled trial, and 3 meta-analyses. Compared with placebo, application of topical indigo naturalis, studied in 5 RCTs with 215 participants, showed significant improvements in the treatment of psoriasis. Treatment with curcumin, examined in 3 RCTs (with a total of 118 participants), 1 nonrandomized controlled study, and 1 uncontrolled study, conferred statistically and clinically significant improvements in psoriasis plaques. Fish oil treatment was evaluated in 20 studies (12 RCTs, 1 open-label nonrandomized controlled trial, and 7 uncontrolled studies); most of the RCTs showed no significant improvement in psoriasis, whereas most of the uncontrolled studies showed benefit when fish oil was used daily. Meditation and guided imagery therapies were studied in 3 single-blind RCTs (with a total of 112 patients) and showed modest efficacy in treatment of psoriasis. One meta-analysis of 13 RCTs examined the association of acupuncture with improvement in psoriasis and showed significant improvement with acupuncture compared with placebo.

Conclusions and Relevance

The CAM therapies with the most robust evidence of efficacy for treatment of psoriasis are indigo naturalis, curcumin, dietary modification, fish oil, meditation, and acupuncture. This review will aid practitioners in advising patients seeking unconventional approaches for treatment of psoriasis.

Combined Systemic and Intratumoral Administration of Human Papillomavirus Vaccine to Treat Multiple Cutaneous Basaloid Squamous Cell Carcinomas

Importance

Squamous cell carcinoma (SCC) is the second most common form of skin cancer, and its incidence is increasing. When surgical management is not an option, finding a safe and efficacious treatment is a challenge. Mounting evidence suggests that the human papillomavirus (HPV) is involved in the pathogenesis of some SCCs.

Objective

To assess whether the 9-valent HPV vaccine could be an effective treatment strategy for cutaneous SCC.

Design, Setting, and Participants

A woman in her 90s with multiple, inoperable cutaneous basaloid SCCs was successfully treated at a university-based outpatient dermatology clinic with a combination of systemic and intratumoral delivery of the 9-valent HPV vaccine from March 17, 2016, through February 27, 2017, and then followed up through May 21, 2018.

Main Outcomes and Measures

Reduction in tumor size and number after a combination of systemic and intratumoral administration of the HPV vaccine.

Results

All tumors resolved 11 months after the first intratumoral injection of the vaccine. The patient remained free of tumors at the end of follow-up.

Conclusions and Relevance

This is the first report, to our knowledge, of complete regression of a cutaneous malignant tumor after combined systemic and direct intratumoral injection of the 9-valent HPV vaccine. This report suggests that the HPV vaccine may have therapeutic utility for SCCs in patients who are poor surgical candidates, have multiple lesions, or defer surgery.

A Biologically Based Approach to Acne and Rosacea

Complementary and alternative medicine (CAM) therapies are increasing in popularity in the field of dermatology. Natural products and holistic approaches are in high demand among patients and research has begun to support their roles in acne and rosacea pathophysiology. In this article, commonly utilized biologically based complementary and alternative therapies for acne and rosacea are reviewed from an evidence-based perspective. Therapies discussed include vitamin C, nicotinamide, zinc, tea tree oil, green tea, resveratrol, curcumin, feverfew, licorice, chamomile, polypodium leucotomos, and nutrition-based approaches. J Drugs Dermatol. 2018;17(6):611-617.

Widespread Skin Necrosis Secondary to Gemcitabine Therapy

Gemcitabine, a pyrimidine nucleoside analogue, is an oncologic agent used in the treatment of cutaneous T-cell lymphoma (CTCL). Common dermatologic reactions associated with gemcitabine include alopecia, mild skin rash, and mucositis but skin necrosis is exceptional. Herein we present an unusual case of widespread skin necrosis mimicking toxic epidermal necrolysis in a 45-year-old woman receiving gemcitabine therapy for stage IIIA cutaneous T-cell lymphoma. This is the first reported case of a TEN-like reaction subsequent to gemcitabine treatment. J Drugs Dermatol. 2018;17(5):582-585.

Association of Human Papillomavirus Vaccine With the Development of Keratinocyte Carcinomas

Importance

Keratinocyte carcinomas (KCs), consisting of squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs), are the most common human malignant neoplasms. Several risk factors have been implicated in KC development. For some SCCs, particularly those in immunocompromised patients, human papillomavirus (HPV) may be an important factor.

Objective

To determine whether quadrivalent HPV vaccination would affect the development of KCs in immunocompetent patients with a history of multiple KCs.

Design, Setting, and Participants

Two patients with a history of multiple KCs-a man in his 70s (patient 1) and a woman in her 80s (patient 2)-were treated in a private dermatology practice. Each patient received 3 doses of the quadrivalent HPV vaccine at 0, 2, and 6 months in 2013, and both patients underwent full-body skin examinations at least every 3 months. Biopsy-proven skin cancers were recorded for 16 months (for patient 1) or 13 months (for patient 2) after the first dose of vaccine and then compared with the number of biopsy-proven skin cancers recorded over a similar period before the first dose of vaccine. The period of observation was from October 18, 2011, to June 21, 2014.

Main Outcomes and Measures

The numbers of new SCCs and BCCs after the first dose of the quadrivalent HPV vaccine.

Results

Patient 1 had a mean of 12 new SCCs and 2.25 new BCCs per year before vaccination. After vaccination, he developed 4.44 SCCs and 0 BCCs per year, a 62.5% reduction in SCCs and a 100% reduction in BCCs. Patient 2 had a mean of 5.5 new SCCs and 0.92 new BCCs per year before vaccination. After vaccination, she developed 1.84 SCCs and 0 BCCs per year, a 66.5% reduction in SCCs and a 100% reduction in BCCs. The quadrivalent HPV vaccine was well tolerated by both patients and had no adverse effects.

Conclusions and Relevance

A reduction of SCCs and BCCs was observed in 2 patients after administration of the quadrivalent HPV vaccine. These findings highlight the possibility that cutaneous SCC development, and perhaps BCC development, may be driven in part by HPV in immunocompetent patients. Human papillomavirus vaccination may represent an efficacious, cost-effective, readily available, and well-tolerated strategy for preventing KCs.

An Open-Label Evaluator Blinded Study of the Efficacy and Safety of a New Nutritional Supplement in Androgenetic Alopecia: A Pilot Study

Objective: To evaluate the effectiveness of a novel oral supplement, Forti5^®, containing green tea extract, omega 3 and 6 fatty acids, cholecalciferol, melatonin, beta-sitosterol, and soy isoflavones, and in the management of subjects with androgenetic alopecia. Design: A prospective case series of 10 subjects. Setting: Open-label, evaluator-blinded, proof-of-concept study. Participants: Ten adult subjects with androgenetic alopecia completed the study. Subjects were not allowed to use oral or topical hair growth products in the 24 weeks preceding the study or during the study. The nutritional supplement was administered at a dosage of two tablets daily for 24 weeks. Measurements: Clinical evaluations were performed at baseline and at 24 weeks. Efficacy was evaluated using hair mass index measured by cross section trichometer, terminal hair count measured with dermoscopy and Investigator Global Photography Assessment. Results: Overall 80 percent of subjects (8/10) were rated as improved after 24 weeks of supplementation (mean change of +1.4 equivalent to slightly-to-moderately increased). Forty percent of subjects (4/10) were rated as moderately improved (2+), and 10 percent (1/10) were rated as greatly improved (3+). There was a significant improvement in terminal hair count (mean increase of 5.9% or 4.2 more terminal hairs in the area examined, p=0.014) and in Hair Mass Index (mean increase of 9.5% or 4.5 higher Hair Mass Index, p=0.003). Conclusion: These preliminary results indicate that Forti5^® a novel nutritional supplement that contains cholecalciferol, omega 3 and 6 fatty acids, melatonin, antioxidants, and botanical 5-alpha reductase inhibitors, may be a useful adjunct in the treatment of androgenetic alopecia.

Isospin Symmetry at High Spin Studied via Nucleon Knockout from Isomeric States

One-neutron knockout reactions have been performed on a beam of radioactive ^{53}Co in a high-spin isomeric state. The analysis is shown to yield a highly selective population of high-spin states in an exotic nucleus with a significant cross section, and hence represents a technique that is applicable to the planned new generation of fragmentation-based radioactive beam facilities. Additionally, the relative cross sections among the excited states can be predicted to a high level of accuracy when reliable shell-model input is available. The work has resulted in a new level scheme, up to the 11^{+} band-termination state, of the proton-rich nucleus ^{52}Co (Z=27, N=25). This has in turn enabled a study of mirror energy differences in the A=52 odd-odd mirror nuclei, interpreted in terms of isospin-nonconserving (INC) forces in nuclei. The analysis demonstrates the importance of using a full set of J-dependent INC terms to explain the experimental observations.

Lewis acid-promoted [2 + 2] cycloadditions of alkenes with aryl ketenes

A method for the [2 + 2] cycloaddition of aryl ketenes and alkenes is presented. The process involves the in situ generation of a ketene in the presence of a Lewis acid. The utility of products is demonstrated towards the synthesis of a common scaffold found in several natural product families.

Ex utero electroporation and whole hemisphere explants: a simple experimental method for studies of early cortical development

Cortical development involves complex interactions between neurons and non-neuronal elements including precursor cells, blood vessels, meninges and associated extracellular matrix. Because they provide a suitable organotypic environment, cortical slice explants are often used to investigate those interactions that control neuronal differentiation and development. Although beneficial, the slice explant model can suffer from drawbacks including aberrant cellular lamination and migration. Here we report a whole cerebral hemisphere explant system for studies of early cortical development that is easier to prepare than cortical slices and shows consistent organotypic migration and lamination. In this model system, early lamination and migration patterns proceed normally for a period of two days in vitro, including the period of preplate splitting, during which prospective cortical layer six forms. We then developed an ex utero electroporation (EUEP) approach that achieves -80% success in targeting GFP expression to neurons developing in the dorsal medial cortex. The whole hemisphere explant model makes early cortical development accessible for electroporation, pharmacological intervention and live imaging approaches. This method avoids the survival surgery required of in utero electroporation (IUEP) approaches while improving both transfection and areal targeting consistency. This method will facilitate experimental studies of neuronal proliferation, migration and differentiation.

Reelin promotes neuronal orientation and dendritogenesis during preplate splitting

The secreted ligand Reelin is thought to regulate the translocation and positioning of prospective layer 6 (L6) neurons into the preplate, a plexus of neurons overlying the ventricular zone. We examined wild type and Reelin-deficient cortices and found that L6 neurons were equivalently positioned beneath the pia during the period of preplate splitting and initial cortical plate (CP) formation. The absence of detectable L6 ectopia in "reeler" cortices at this developmental time point indicates that Reelin-signaling might not regulate L6 neuron migration or gross positioning during preplate splitting. To explore the acute response of L6 neurons to Reelin, subpial injections of Reelin were made into Reelin-deficient explants. Reelin injection caused L6 neurons to orient their nuclei and polarize their Golgi toward the pia while initiating exuberant dendritic (MAP2+) outgrowth within 4 h. This rapid Reelin-dependent neuronal orientation and alignment created CP-like histology without any significant change in the mean position of the population of L6 neurons. Conversely, subplate cells and chondroitin sulfate proteoglycan immunoreactivity were found at significantly deeper positions from the pial surface after injection, suggesting that Reelin partially rescues preplate splitting within 4 h. Thus, Reelin has a direct role in promoting rapid morphological differentation and orientation of L6 neurons during preplate splitting.

Comparison of slow and fast neocortical neuron migration using a new in vitro model

BACKGROUND

Mutations, toxic insults and radiation exposure are known to slow or arrest the migration of cortical neurons, in most cases by unknown mechanisms. The movement of migrating neurons is saltatory, reflecting the intermittent movement of the nucleus (nucleokinesis) within the confines of the plasma membrane. Each nucleokinetic movement is analogous to a step. Thus, average migration speed could be reduced by lowering step frequency and/or step distance.

RESULTS

To assess the kinetic features of cortical neuron migration we developed a cell culture system that supports fiber-guided migration. In this system, the majority of fiber-apposed cells were neurons, expressed age-appropriate cortical-layer specific markers and migrated during a 30 min imaging period. Comparison of the slowest and fastest quartiles of cells revealed a 5-fold difference in average speed. The major determinant of average speed in slower cells (6-26 microm/hr) was step frequency, while step distance was the critical determinant of average speed in faster cells (>26 microm/hr). Surprisingly, step distance was largely determined by the average duration of the step, rather than the speed of nucleokinesis during the step, which differed by only 1.3-fold between the slowest and fastest quartiles.

CONCLUSION

Saltatory event frequency and duration, not nucleokinetic speed, are the major determinants of average migration speed in healthy neurons. Alteration of either saltatory event frequency or duration should be considered along with nucleokinetic abnormalities as possible contributors to pathological conditions.

Resistance to the orexigenic effect of ghrelin in dietary-induced obesity in mice: reversal upon weight loss

BACKGROUND

Ghrelin, an endogenous ligand for growth hormone secretagogue receptor (GHS-R), is known to increase food intake in lean humans and rodents. In addition, ghrelin levels are increased by fasting in lean rodents and are elevated before meals in humans, suggesting an important role for ghrelin in meal initiation. However, in obese human, circulating ghrelin levels were found to be significantly reduced as compared to lean individuals.

OBJECTIVES

To evaluate whether circulating ghrelin levels, as well as ghrelin sensitivity, are decreased in obese individuals in order to limit its effect on food intake.

DESIGN

: Lean C57BL/6J mice fed a chow, a low- (LFD) or a high-fat diet (HFD) were used to determine ghrelin regulation and secretion as well as ghrelin sensitivity.

MEASUREMENTS

Plasma ghrelin levels were measured in low- and high-fat fed mice. Ghrelin-induced food intake was measured in chow, low- and high-fat fed mice.

RESULTS

We measured ghrelin levels in lean and diet-induced obese mice, fed on an LFD or an HFD, respectively. We observed that not only ghrelin secretion was reduced in obese mice but its diurnal regulation was also lost. In addition, we failed to observe any change in ghrelin secretion upon fasting and refeeding. Moreover, we observed that the sensitivity to the orexigenic effects of exogenous ghrelin was reduced in obese mice when compared to lean mice fed a chow or a LFD. The insensitivity of obese mice to ghrelin was improved upon weigh loss.

CONCLUSION

: Altogether, these results indicate that ghrelin secretion and regulation is impaired in dietary-induced obesity in mice and suggest that ghrelin inhibition could prevent weight regain after weight loss.

Effect of rainbow trout growth hormone complementary DNA on body shape, carcass yield, and carcass composition of F1 and F2 transgenic common carp (Cyprinus carpio)

The effect of rainbow trout growth hormone complementary DNA on body shape, dress-out yield, and body composition were assessed in the F1 and F2 generations of transgenic common carp (Cyprinus carpio). All measurements were compared with those for nontransgenic full-sibling common carp in their respective families, and the fish were communally evaluated in earthen ponds. The body weight and length were highly correlated (P <0.01) in both genotypes in all the families. Head morphometrics were negatively correlated (P <0.05) to weight and length of the fish. Various head, body, and caudal traits grew disproportionately faster in transgenic fish in both generations. The altered body shape of transgenic fish resulted in improved dressing percentage in the F2 generation. The carcass composition of transgenic muscle had a lower percentage of (P <0.01) moisture and lipids and higher (P <0.01) percentage of protein in both generations. Six of the 18 amino acids analyzed in F1 transgenic common carp muscle were higher F1 (P <0.05) than the control genotype; however, amino acid ratios were minimally changed. Also, the fatty acid profiles of both genotypes were minimally altered. Higher histidine and lysine ratios in the diet are recommended for maximum growth and health of transgenic common carp in intensive culture systems on the basis of essential amino acid ratios.

Influence of environmental salinity on messenger RNA levels of growth hormone, prolactin, and somatolactin in pituitary of the channel catfish (Ictalurus punctatus)

Pituitary growth hormone (GH), prolactin (PRL), and somatolactin (SL) messenger RNA levels in channel catfish (Ictalurus punctatus) were examined under various environmental and physiological conditions. Catfish were sampled following salinity challenge, during the winter (December) and spring or summer (April or July), and at different sizes (15-18 g, 620-664 g, and 956-1134 g). When catfish (956-1134 g) were transferred from freshwater to saline water containing 8 ppt NaCl, their plasma [Na(+)] increased significantly above values in the freshwater control group until they were transferred back to freshwater. Pituitary GH mRNA levels were low for the first 24 hours following transfer to saline water, but thereafter were significantly elevated above control values until the fish were transferred back to freshwater. Pituitary GH mRNA levels were highest in July and lowest in December. Growth hormone mRNA levels were also elevated in the size groups 15-18 g and 956-1134 g in July when compared with December values. Pituitary PRL mRNA levels increased for the first 24 hours following transfer to saline water (956-1134 g), but thereafter were significantly lower than control values until the fish were transferred back to freshwater. Pituitary PRL mRNA levels were highest in April and July and lowest in December, and were also elevated in the size groups 620-664 g and 956-1134 g. Pituitary SL mRNA levels were unaffected in catfish transferred to saline water; however, levels were significantly elevated in catfish of the 956-1134-g size group sampled in April when compared with December. These results suggest the involvement of GH in adaptation to brackish water and of PRL in adaptation to freshwater in the catfish, and seasonal and size-related differences in pituitary GH, PRL, and SL mRNA levels.

Antithrombotic efficacy of a novel murine antihuman factor IX antibody in rats

A murine antihuman factor IX monoclonal antibody (BC2) has been generated and evaluated for its capacity to prolong the activated partial thromboplastin time (aPTT) in vitro and ex vivo and to prevent arterial thrombosis in a rat model in vivo. BC2 extended aPTT to a maximum of 60 to 80 seconds at 100 to 1000 nmol/L in vitro (rat and human plasma, respectively) and ex vivo (rat) after dosing of rats up to 6 mg/kg in vivo. BC2, administered as bolus (1 to 6 mg/kg) followed by infusion (0.3 to 2 mg x kg(-1) x h(-1)), dose-dependently prevented thrombosis of an injured rat carotid artery (FeCl(3)-patch model), increased time to artery occlusion, and reduced incidence of vessel occlusion. BC2 efficacy in preventing arterial thrombosis exceeded that of heparin (bolus 15 to 120 U/kg followed by infusion 0.5 to 4.0 U x kg(-1) x min(-1)), whereas the latter rendered the blood incoagulable (aPTT>1000 seconds). BC2 demonstrated complete antithrombotic efficacy also as a single bolus given either as prevessel or postvessel injury as evidenced by reduction of thrombus mass (from 4.18+/-0.49 to 1.80 +/-0.3 mg, P<0.001), increasing vessel patency time (from 14.9+/-0.9 minutes to 58.3+/-1.7 minutes, P<0.001) and decreasing incidence of vessel occlusion from 100% to 0% in vehicle- versus BC2-treated rats, respectively. BC2 (3 mg/kg, IV) administered in a single bolus resulted in 50% reduction in thrombus mass (P<0.01), extended vessel patency time (P<0.001), extended aPTT only 4-fold, and had no effect on blood loss via a tail surgical wound; heparin, at doses that reduced thrombus mass to a similar extent, extended aPTT beyond 1000 seconds (over 500-fold) and increased blood loss from 1.8+/-0.7 to 3.3 +/-0.6 mL (P<0.001). These data suggest that BC2 may provide enhanced therapeutic efficacy in humans at lesser interference with blood hemostasis than heparin.

SB 209670 inhibits the arrhythmogenic actions of endothelin-1 in the anesthetized dog

SB 209670 reduced basal mean arterial pressure (16%) without affecting left-circumflex coronary artery (LCX) flow, cardiac output, heart rate, or global/regional myocardial contractility. In vehicle-treated animals, i.e. endothelin (ET)-1 produced an initial hyperemic response in the LCX, followed by a secondary reduction in flow. This response was accomplished by decreases in LCX regional wall fractional shortening, +dP/dt and -dP/dt, but an increase in left anterior wall fractional shortening. ET-1 also produced dose-related, fatal ventricular fibrillation. Whereas SB 209670 administration did not inhibit the initial increase in coronary flow produced by ET-1, the secondary constrictor responses were markedly antagonized. SB 209670 also attenuated the reduction in LCX regional wall fractional shortening and converted the increase in left anterior wall contractility to a reduction in contractility. Although SB 209670 produced only a modest inhibition of the ET-1-mediated reductions in dP/dt, the induction of fatal ventricular arrhythmias was completely abolished. Therefore, the data are consistent with the hypothesis that the coronary ischemic and proarrythmic actions of ET-1 are distinct. Therefore, ET receptor antagonists may be useful in treatment of disturbances in cardiac rhythm.

Binding of [3H]-SK&F 107260 and [3H]-SB 214857 to purified integrin alphaIIbbeta3: evidence for a common binding site for cyclic arginyl-glycinyl-aspartic acid peptides and nonpeptides

The aggregation of activated platelets is mediated by the binding of fibrinogen to its cell surface receptor, the integrin alphaIIbbeta3. The recognition of fibrinogen by alphaIIbbeta3 depends, in part, on the tripeptide sequence Arg-Gly-Asp (RGD) in the adhesive protein. The interactions of a cyclic RGD-containing pentapeptide, [3H]-SK&F-107260, and a 1,4-benzodiazepine-based nonpeptide [3H]-SB-214857, with purified alphaIIbbeta3 have been investigated. Both compounds potently inhibit platelet aggregation at submicromolar concentrations. Binding of both [3H]-SK&F-107260 (Kd = 1.19 nM) and [3H]-SB-214857 (Kd = 1.85 nM) to alphaIIbbeta3 is of high affinity and fully reversible. The binding is monophasic, indicating a single class of noncooperative binding sites. The two radioligands exhibited similar values in binding to alphaIIbbeta3 purified on an RGD-affinity column (Bmax = 0.2 mol/mol alphaIIbbeta3) or to alphaIIbbeta3 purified over a lentil lectin column (Bmax = 0.03 mol/mol alphaIIbbeta3), suggesting that SK&F-107260 and SB-214857 interact with the same population of receptors. Binding of [3H]-SK&F-107260 and [3H]-SB-214857 to alphaIIbbeta3 require divalent cations, Mg++, Ca++ and Mn++ are able to support binding, with Mn++ being the most effective. Thirteen alphaIIbbeta3 antagonists, including four linear and three cyclic RGD peptides, five peptidomimetics, the fibrinogen gamma-chain dodecapeptide (HHLGGAKQAGDV) and the snake venom protein, echistatin, complete for [3H]-SK&F-107260 or [3H]-SB-214857 binding to alphaIIbbeta3. The affinity constants (Ki) of these compounds, determined by the two radioligand binding assays, are similar. Furthermore, these compounds exhibit the same rank order of potency in inhibiting biotinylated-fibrinogen binding to alphaIIbbeta3. Scatchard plot analyses of the [3H]-SK&F-107260 binding isotherms in the presence of unlabeled SB-214857 and gamma-chain dodecapeptide reveal competitive-type antagonism, indicating that SB-214857, gamma-chain dodecapeptide and SK&F-107260 interact with mutually exclusive binding sites on alphaIIbbeta3.

Antifibrillatory effects of BRL-32872 in anesthetized Yucatan minipigs with regional myocardial ischemia

The antifibrillatory potential of BRL-32872, a novel antiarrhythmic compound with K+ and Ca2+ channel blocking activities, was examined in a minipig model of ischemia-induced arrhythmia. The effects of intravenous (i.v.) BRL-32872 (0.3 and 1.0 mg/kg, n = 8), dofetilide (0.3 mg/kg, n = 8), and flecainide (2.0 mg/kg, n = 8), were investigated on the incidence of ventricular fibrillation (VF) during a 20-min occlusion of the left anterior descending coronary artery (LAD). Ischemia-induced VF occurred in 6 of 9 vehicle-treated pigs. BRL-32872 reduced the incidence of ischemic VF to 13% at 0.3 mg/kg (p < 0.05) and to 0% at 1.0 mg/kg (p < 0.01). Dofetilide also prevented the occurrence of VF (0%, p < 0.01) In contrast, flecainide did not reduce the incidence of VF (63%). Indeed, flecainide shortened the time to onset of VF from 17 +/- 1 min in the vehicle group to 10 +/- 1 min (p < 0.001). The antifibrillatory effects of BRL-32872 and dofetilide were associated with a prolongation of QT interval on ECG. Flecainide did not prolong repolarization, but slowed the ventricular conduction velocity, as shown by significant increases in PR and QRS intervals. During early reperfusion, 1 of 8 surviving pigs in each group treated with BRL-32872 and 4 of 8 in the dofetilide group developed VF. This study demonstrated an antifibrillatory effect of BRL-32872 associated with prolonged ventricular repolarization and showed enhanced efficacy over dofetilide on reperfusion arrhythmias which is most likely a consequence of its Ca2+ blocking activity.

Cardioprotection and thrombolysis by anistreplase in anesthetized dogs

Anistreplase is a thrombolytic agent comprising a complex of streptokinase, lys-plasminogen, and a p-anisoyl group, which temporarily protects the catalytic center of the enzyme complex. Streptokinase was previously shown to reduce infarct size (IS) in dogs with a fibrin-rich clot in the left anterior descending coronary artery (LAD) without necessarily producing reperfusion. Therefore, we hypothesized that IS in this model would be reduced by anistreplase. In addition, we studied the effect of tissue-type plasminogen activator (t-PA) on IS, testing our hypothesis in anesthetized dogs in which thrombin (100 U) and calcium (50 microliters, 0.05 M) were sequentially injected into the LAD to form a thrombus, anistreplase [0.01, 0.05, or 0.10 U/kg intravenous (i.v.) bolus], t-PA (0.1, 0.5, 2, or 8 micrograms/kg/min infusion for 60 min) or vehicle (VEH) was administered 55 min later. Anistreplase (0.05 or 0.10 U/kg) significantly (p < 0.05) reduced clot weight (VEH 22 +/- 3 mg; anistreplase 0.05 U/kg, 13 +/- 4 mg; anistreplase 0.10 U/kg, 0.7 +/- 0.6 mg), increased incidence of reperfusion (VEH 0%; anistreplase 0.05 U/kg, 42%; anistreplase 0.10 U/kg, 100%) and reduced IS (VEH 23 +/- 3%; anistreplase, 0.05 U/kg, 14 +/- 2%; anistreplase 0.10 U/kg, 15 +/- 2%). t-PA reduced thrombin weight (VEH 26 +/- 3 mg; 2 micrograms/kg/min t-PA 12 +/- 4; 8 micrograms/kg/min t-PA 2 +/- 2 mg) and increased incidence of reperfusion (VEH 0%; 2 micrograms/kg/min 75%; 8 micrograms/kg/min 100%), but IS was not altered (VEH 19 +/- 3%; 0.1 microgram/kg/min 18 +/- 3%; 0.5 microgram/kg/min 23 +/- 2%; 2 micrograms/kg/min 16 +/- 5%; 8 micrograms/kg/min: 19 +/- 3%).(ABSTRACT TRUNCATED AT 250 WORDS)

The in vivo pharmacological profile of the novel glycoprotein IIb/IIIa antagonist, SK&F 106760

The in vivo pharmacological profile of SK&F 106760 [N alpha-acetyl-cyclo(S,S)-cysteinyl-N alpha-methylarginyl-glycyl-aspartyl-penicillamine-amide], a novel, potent glycoprotein IIb/IIIa (GPIIb/IIIa) antagonist has been investigated. In conscious dogs, SK&F 106760 (0.3-3 mg/kg i.v.) produced a dose-related inhibition of ex vivo whole blood platelet aggregation induced by collagen (5 micrograms/ml) with complete inhibition being produced for 5, 90 and 165 min after administration of 0.3, 1 and 3 mg/kg i.v., respectively. Plasma levels of SK&F 106760 were measured by high-performance liquid chromatography after i.v. bolus administration of 1 mg/kg. An initial alpha-disposition phase with a T1/2 of 11 +/- 6 min was followed by a longer terminal beta-elimination phase with a T1/2 of 66 +/- 12 min, which accounted for 79 +/- 9% of the total area under the plasma concentration-time curve. The apparent steady-state volume of distribution was 259 +/- 26 ml/kg and the plasma clearance was 3.4 +/- 0.8 ml/min/kg. The plasma concentration of SK&F 106760 at which collagen-induced ex vivo whole blood aggregation was inhibited by 50% was estimated to be 593 +/- 52 nM. After intraduodenal and intrajejunal administration of 3 mg/kg, SK&F 106760 had a bioavailability of 3 to 6% and produced a peak inhibition of ex vivo platelet aggregation of 40 to 50%. In anesthetized dogs, SK&F 106760 (0.3-3.0 mg/kg i.v.) produced a complete inhibition of platelet-dependent coronary artery thrombosis, with a dose-related duration of action.(ABSTRACT TRUNCATED AT 250 WORDS)

The in vitro pharmacological profile of SK&F 106760, a novel GPIIB/IIIA antagonist

The properties of SK&F 106760 [N alpha-acetyl-cyclo(S,S)-cysteinyl-N alpha-methyl-arginyl-glycyl-aspartyl-penicillamine-amide] as a GPIIb/IIIa antagonist have been studied in vitro and compared with those of the parent molecule, Ac-RGDS-NH2. Ac-RGDS-NH2 inhibited biotinylated fibrinogen binding to purified human GPIIb/IIIa immobilized on plastic microtitre plates with a Ki of 530 +/- 73 nM. In canine platelet rich plasma Ac-RGDS-NH2 produced a concentration related inhibition of adenosine diphosphate-induced platelet aggregation following preincubation for 3 min with an IC50 of 91 +/- 1 microM. However, incubation in platelet rich plasma for 3 hr abolished the activity of Ac-RGDS-NH2. SK&F 106760 inhibited biotinylated fibrinogen binding to purified human GPIIb/IIIa immobilized on plastic microtitre plates with a Ki of 477 +/- 57 pM. SK&F 106760 inhibited adenosine diphosphate-induced platelet aggregation in human platelet rich plasma with an IC50 of 230 +/- 60 nM but did not inhibit the von Willebrand Factor receptor (GPIb/IX)-mediated platelet agglutination produced by ristocetin. In canine platelet rich plasma SK&F 106760 inhibited aggregation produced by adenosine diphosphate, collagen and epinephrine/U-46619 with IC50 values of 355 +/- 35, 260 +/- 20, and 490 +/- 90 nM, respectively and in gel filtered platelets inhibited thrombin-mediated aggregation with an IC50 of 188 +/- 10 nM. Preincubation of SK&F 106760 in platelet rich plasma for three hours had no significant effect on its ability to inhibit adenosine diphosphate-induced platelet aggregation. SK&F 106760 produced insurmountable inhibition of adenosine diphosphate-induced platelet aggregation in the presence of constant fibrinogen concentrations, but produced competitive inhibition of the concentration-response curve to fibrinogen in adenosine diphosphate-activated platelets with a Kb of 8.0 +/- 1.0 nM. Thus, SK&F 106760 is a potent, stable competitive GPIIb/IIIa antagonist with no detectable activity at the von Willebrand Factor receptor (GPIb/IX).

Conformationally constrained peptides and semipeptides derived from RGD as potent inhibitors of the platelet fibrinogen receptor and platelet aggregation

Structure-activity studies have been pursued on cyclo-S,S-[Ac-Cys-(N alpha-Me)Arg-Gly-Asp-Pen]-NH2, 2 (SK&F 106760), a potent inhibitor of platelet aggregation, in an effort to improve potency and affinity for the GPIIb/IIIa receptor. Modifications on the N- and C-termini of 2 produced a series of peptides which indicate that the C-terminal carboxylate group may be a secondary receptor-binding element. Further modification by replacing the disulfide tether N alpha-acetylcysteine/penicillamineamide with the novel, inexpensive, achiral, constrained, and more lipophilic tether 2-mercaptobenzoyl/2-mercaptoaniline (Mba/Man) afforded the semipeptide cyclo-S,S-[Mba-(N alpha-Me)Arg-Gly-Asp-Man], 18 (SK&F 107260), which exhibited significant enhancement in both affinity and potency. To further investigate the effect of the phenyl ring at the C-terminus, peptides bearing the novel (2R,3S)- and (2R,3R)-beta-phenylcysteines were synthesized, which culminated in the cyclo-S,S-[Ac-Cys-(N alpha-Me)Arg-Gly-Asp-(2R,3S)-beta-phenylCys]-OH peptide, 22, which displayed substantial affinity and potency. We describe, herein, the development of both 18 and 22 and the additional structural modifications within the constrained cyclic disulfide ring to probe the stereochemical and steric requirements for receptor interaction.

A chronic Access Port model for direct delivery of drugs into the intestine of conscious dogs

Gastric physiologic properties and emptying can significantly affect the stability and absorption of drugs given orally. A method to deliver drugs directly into the intestines and peritoneal cavity in conscious dogs by using a modified Vascular-Access Port (VAP) was developed and validated. Modified silastic VAP catheters size 7 or 9 French were placed in the duodenum, jejunum, colon, and/or peritoneal cavity in nine adult male dogs. Catheter placement was validated in six dogs by using contrast radiography and by monitoring the fecal excretion of blood after injection of blood via the VAP directly into the intestines. Three dogs were successfully used to evaluate the absorption of a peptide that inhibits platelet aggregation. Results showed this to be a feasible, easily validated model for delivering drugs directly into the intestines of conscious dogs.

Development of GPIIb/IIIa antagonists as antithrombotic drugs

Thrombosis represents a major target for development of drugs to prevent and treat a variety of cardiovascular and cerebrovascular diseases, which are the leading cause of morbidity and mortality in the Western world. This review by Andy Nichols and colleagues focuses on a central process in thrombosis, namely platelet aggregation, and how it can be inhibited by antagonists of the adhesion molecule GPIIb/IIIa. Successful and future therapeutic applications of GPIIb/IIIa antagonists, and their pharmacology, are considered in detail.

Receptor protection studies with phenoxybenzamine indicate that a single alpha 1-adrenoceptor may be coupled to two signal transduction processes in vascular smooth muscle

Full alpha 1-adrenoceptor agonists, such as (-)-norepinephrine, produce vasoconstriction in the rat aorta primarily through the mobilization of intracellular stores of calcium, whereas partial alpha 1-adrenoceptor agonists, such as (-)-dobutamine, produce vasoconstriction primarily through the translocation of extracellular calcium. The different pools of calcium utilized by full and partial alpha 1-adrenoceptor agonists have been proposed to result from the activation of different alpha 1-adrenoceptor subtypes. The irreversible alpha 1-adrenoceptor antagonist, phenoxybenzamine, selectively eliminates only that component of an alpha 1-adrenoceptor-mediated response in the rat aorta that is dependent upon the mobilization of intracellular stores of calcium. In order to determine whether in the rat aorta there exist two distinct alpha 1-adrenoceptor subtypes linked separately to the mobilization of intracellular and extracellular calcium, we utilized the full and partial alpha 1-adrenoceptor agonists, (-)-norepinephrine and (-)-dobutamine, respectively, and the irreversible antagonist, phenoxy-benzamine, as pharmacologic tools in a classical receptor-protection study to probe these alpha 1-adrenoceptor-mediated vasoconstrictor process(es). Our logic was that if the intracellular and extracellular pools of calcium were coupled to different alpha 1-adrenoceptor subtypes, then only (-)-norepinephrine, and not (-)-dobutamine, would protect against alpha 1-adrenoceptor alkylation by phenoxybenzamine, since phenoxybenzamine only eliminates the process that depends on intracellular calcium. Alternatively, if both (-)-norepinephrine and (-)-dobutamine produce a similar degree of alpha 1-adrenoceptor protection against phenoxybenzamine, our results would suggest that a single alpha 1-adrenoceptor subtype exists which activates both the translocation of extracellular calcium and the mobilization of intracellular calcium. Phenoxybenzamine (30 nM) abolished contractions of the rat aorta produced by (-)-norepinephrine, as expected. Pretreatment of the tissues with either (-)-norepinephrine or (-)-dobutamine, at concentrations that produced equivalent degrees of alpha 1-adrenoceptor occupancy, resulted in equal protection against alkylation of alpha 1-adrenoceptors by phenoxybenzamine, arguing against the existence of two distinct alpha 1-adrenoceptor subtypes in the rat aorta. These results are consistent with our previous hypothesis that two different signal-transduction processes may be activated in the rat aorta by a single alpha 1-adrenoceptor population, with the intrinsic efficacy of the agonist determining which signal-transduction process is activated.

Antithrombotic effects of a platelet fibrinogen receptor antagonist in a canine model of carotid artery thrombosis

BACKGROUND AND PURPOSE

Platelet-fibrin thrombi in the lumen of atherostenotic carotid arteries may underlie transient ischemic attacks and cerebral infarction. For this reason, we investigated the antiplatelet and antithrombotic effects of a novel and potent platelet fibrinogen receptor (glycoprotein IIb/IIIa) antagonist (SK&F 106760).

METHODS

The effects of 0.1-3.0 mg/kg i.v. SK&F 106760 on platelet aggregation were examined ex vivo in canine platelet-rich plasma (n = 20). In addition, the antithrombotic effects of SK&F 106760 were compared with those of aspirin in an acute canine model of extracranial carotid artery thrombosis with high-grade stenosis. Sham-operated (n = 4), vehicle-treated (n = 6), SK&F 106760-treated (n = 8), aspirin-treated (n = 9), and SK&F 106760+aspirin-treated (n = 5) dogs were examined.

RESULTS

The intravenous administration of SK&F 106760 caused a dose-related inhibition of ex vivo platelet aggregation. In the carotid artery thrombosis model, an occlusive thrombus formed at stenotic sites in the region of the carotid bifurcation. The thrombogenic process caused a progressive reduction in carotid blood flow and reduced the cortical microvascular perfusion and electroencephalographic power. Based on nuclear magnetic resonance spectroscopy, the occlusive events depleted the stores of high-energy phosphates (adenosine triphosphate and phosphocreatine) and increased the lactate concentration in the forelimb somatosensory area of the parietal cortex. In this model, the administration of 1 mg/kg i.v. SK&F 106760 prevented thrombosis of the stenotic carotid artery. Consequently, neurophysiological, cerebral hemodynamic, and metabolic parameters were all improved significantly in the SK&F 106760-treated group. No dog receiving SK&F 106760 reoccluded during the 1-hour posttreatment observation period. In contrast, thrombosis of the carotid artery was associated with neurophysiological deterioration in six of the nine dogs treated with 5 mg/kg i.v. aspirin. Both spontaneous and evoked (increased carotid stenosis) aspirin-resistant thrombosis were abolished by SK&F 106760 treatment.

CONCLUSIONS

These results suggest that antagonism of fibrinogen binding to platelet glycoprotein IIb/IIIa (the final common pathway for aggregation) may represent a new and more effective antithrombotic approach to the treatment of cerebral transient ischemic attacks and infarction associated with extracranial carotid artery disease.

Cardiovascular actions of a new selective postjunctional alpha-adrenoceptor antagonist, SK&F 104856, in normotensive and hypertensive dogs

1. SK&F 104856 (2-vinyl-7-chloro-3,4,5,6-tetrahydro-4- methylthieno[4,3,2ef][3]benzazepine) is a novel postjunctional alpha 1- and alpha 2-adrenoceptor antagonist. 2. SK&F 104856 as well as prazosin and SK&F 86466 reduced blood pressure in the anaesthetized normotensive dog. 3. SK&F 86466 and rauwolscine but not SK&F 104856 or prazosin, produced a marked increase in myocardial contractility which corresponds with their ability to block prejunctional alpha 2-adrenoceptors. 4. Intravenous or oral administration of SK&F 104856 resulted in dose-dependent antihypertensive responses in 1-kidney, 1-clip (1-K, 1-C) Goldblatt hypertensive dogs with baseline blood pressure of approximately 140 mmHg. At 0.1 and 1 mg kg-1, i.v., mean arterial blood pressure fell by 11 +/- 5 and 23 +/- 5 mmHg, respectively. At 3 and 10 mg kg-1, p.o., blood pressure fell by 9 +/- 3 and 22 +/- 5 mmHg, respectively. At 10 mg kg-1, p.o., the antihypertensive effect of SK&F 104856 was still evident at 4 h. 5. The data indicate that SK&F 104856 shows selectivity in vivo for postjunctional versus prejunctional alpha-adrenoceptors and is a potent and long-acting antihypertensive agent in 1-K, 1-C Goldblatt hypertensive dogs.

Effect of fenoldopam on the acute and subacute nephrotoxicity produced by amphotericin B in the dog

The effect of the selective dopamine DA1 receptor agonist fenoldopam (1 microgram/kg/min i.v.) on the acute nephrotoxic response to amphotericin B (2 mg/kg i.v.) has been studied in the anesthetized dog. Animals were prepared for the measurement of blood pressure, renal blood flow, urine flow, glomerular filtration rate and sodium and potassium excretion. Amphotericin B was given over 20 min and the animals were followed for an additional 160 min. The fenoldopam infusion was started 20 min before amphotericin B and was continued for the duration of the experiment. In control animals, amphotericin B markedly increased renal vascular resistance without affecting blood pressure and thus produced a significant reduction in renal blood flow. The renal vasoconstrictor response to amphotericin B was not attenuated by fenoldopam. Concomitant with the renal vasoconstriction produced by amphotericin B was a marked reduction in glomerular filtration rate, sodium excretion and urine flow rate, which lasted for at least 160 min after amphotericin B treatment. Fenoldopam did not have any effect on the initial reductions in glomerular filtration rate, sodium excretion and urine flow rate but did produce a significant return of these parameters toward control levels by 160 min, despite the continued renal vasoconstriction. The effect of fenoldopam (0.5 microgram/kg/min) given continuously by i.v. infusion on the subacute nephrotoxic response produced by amphotericin B given every other day for 8 days was also investigated. One day after the start of the fenoldopam infusion, venous samples were drawn for the analysis of serum creatinine and blood urea nitrogen.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effect of Pertussis Toxin Treatment on Alpha-1-Adrenoceptor-Mediated Pressor Responses in the Pithed Rat: Dependence on Agonist Efficacy but Not Chemical Class

The role of pertussis-toxin-sensitive guanine nucleotide regulatory proteins (G proteins) in the signal transduction processes involved in post-junctional vascular alpha 1-adrenoceptor-mediated vasoconstriction has been investigated in the pithed rat using two chemical classes of alpha-adrenoceptor agonists, the phenethylamines and imidazolines, in order to determine if they utilize different signal transduction mechanisms. Pertussis toxin pretreatment (50 micrograms/kg, i.v., 3 days prior to experimentation) slightly inhibited the pressor response to the full alpha 1-adrenoceptor agonist of the phenethylamine class (-)-norepinephrine (in the presence of rauwolscine, 1 mg/kg, i.v.), whereas it markedly inhibited the pressor response to the partial alpha 1-adrenoceptor agonist of the imidazoline class oxymetazoline (in the presence of rauwolscine, 1 mg/kg, i.v.). However, after elimination of the alpha 1-adrenoceptor reserve for (-)-norepinephrine with phenoxybenzamine (0.1 mg/kg, i.v.), the pressor response to this agonist became sensitive to inhibition by pertussis toxin treatment. The pattern of inhibition of alpha 1-adrenoceptor-mediated pressor responses produced by pertussis toxin was similar to that produced by the calcium channel antagonist nifedipine (1 mg/kg, i.a.). The results support the hypothesis that vascular alpha 1-adrenoceptors may be coupled to a G protein which is sensitive to pertussis toxin and which couples the alpha 1-adrenoceptor to the influx of extracellular calcium, which possibly another G protein that is insensitive to pertussis toxin that couples the alpha 1-adrenoceptor to the release of intracellular calcium. The intrinsic efficacy of the agonist, and not its chemical class, determines which signal transduction mechanisms will be utilized.

Reduction in myocardial ischemic/reperfusion injury and neutrophil accumulation after therapeutic administration of streptokinase

The benefit of thrombolytic agents to reduce myocardial infarct size, improve left ventricular (LV) function, and prolong survival in human subjects is generally recognized, although the precise mechanism is poorly defined. This study was designed to evaluate the cardioprotective effects of streptokinase (SK) in rats, a species less responsive to plasminogen activators, using a model of mechanical occlusion and release of the left coronary artery. Myocardial injury and polymorphonuclear leukocyte (PMN) infiltration were determined by measuring creatine phosphokinase (CPK) specific activity and myeloperoxidase (MPO) activity, respectively, in the LV free wall (LVFW). After coronary artery occlusion for 0.5 h and reperfusion for 24 h (myocardial ischemia, MI/R), CPK specific activity decreased from 7.0 +/- 0.3 U/mg protein in the sham + vehicle group to 5.6 +/- 0.5 U/mg protein in the MI/R + vehicle group (n = 19, p less than 0.01), while MPO activity increased from 0.14 +/- 0.03 U/g tissue in the sham + vehicle group to 2.8 +/- 0.7 U/g in the MI/R + vehicle group (p less than 0.001). Administration of SK (100,000 IU/kg + 50,000 IU/kg/h for 2 h beginning 15 min before coronary artery reperfusion) reduced the loss of CPK specific activity from reperfused myocardium (6.8 +/- 0.5 U/mg protein, n = 23, p less than 0.05 as compared with the MI/R + vehicle group) and attenuated the increase in MPO activity (1.3 +/- 0.4 U/g tissue, p less than 0.05 as compared with the MI/R + vehicle group). This dose of SK did not change plasma fibrinogen concentration, slightly reduced plasminogen activity (i.e., 20% from control value), and markedly reduced alpha 2-antiplasmin activity (i.e., 60% from control values). A lower dose of SK (i.e., 10,000 IU/kg + 5,000 IU/kg/h for 2 h) did not reduce myocardial injury, did not attenuate the increase in MPO activity, and had no effect on the measured hemostatic parameters. Survival in all MI/R groups ranged from 62 to 66%, and there were no differences in survival between any of the groups (p greater than 0.05). In a model of arachidonic acid-induced rat hindpaw inflammation, SK had no effect on the increase in MPO activity, suggesting that the increase in myocardial MPO activity was not due to a direct effect on inflammatory cell accumulation. In in vitro studies, SK (1-1,000 U/ml) did not scavenge superoxide anion produced by purine (10 mM) and xanthine oxidase (10 mU/ml), nor did it reduce superoxide release, beta-glucuronidase release, or neutrophil aggregation of rabbit peritoneal neutrophils activated with fMLP.(ABSTRACT TRUNCATED AT 400 WORDS)