Fat Embolism Does Not Alter Cardiac Structure or Induce Pathological Changes in a Rat Model.

INTRODUCTION: Fat embolism (FE) encompasses conditions in which fatty substance becomes embedded in a tissue/organ. Fat emboli most commonly affect the lungs in a trauma setting. This can lead to both significant pathology locally and systemically including changes in structure, inflammatory response, activation of the renin-angiotensin system, and subsequent hypoxia. In fact, changes in skin, brain, lungs, and kidneys have been noted in FE syndrome. Because there is an extensive record of pathology reports on this condition without evidence of direct cardiac involvement, as well as our studies showing apparent complete recovery after the acute embolism, we hypothesized that structural changes similar to the lung and at the same time course would not be observed in the heart. METHODS: We used a rat model of FE previously described by our group where we have documented significant lung pathology. In this study, we analyzed both pulmonary and cardiac structure, histology, and gene expression at 48 h and 10 wks post fat injection to mimic FE. RESULTS: Despite severe inflammatory evidence and structural changes to the lung and vasculature up to 10 wks after FE, we found no significant alterations to cardiovascular morphometry including lumen patency ratio, adventitia/media ratio, fibrosis content, and heart chamber/wall dimensions in stained histological sections. Additionally, genetic markers of cardiac pathological hypertrophy were not significantly elevated 48 h or 10 wks after fat treatment. Oil Red O staining showed increased fat droplet content within lung and aorta tissue, but not in the myocardium. CONCLUSIONS: Our study suggests that, in contrast to the lungs, the heart is more resistant to the inflammatory and remodeling responses that result from FE, possibly due to the organ-specific differences in fat retention.

Renin-Angiotensin Blockade Reduces Readmission for Acute Chest Syndrome in Sickle Cell Disease.

Rationale Acute chest syndrome (ACS) is a life-threatening complication of sickle cell disease (SCD). Current treatment is supportive-supplemental oxygen, transfusions, and antibiotics. Prevention of ACS may reduce morbidity and mortality in patients with SCD. Acute chest syndrome appears similar to pulmonary fat embolism (PFE), a complication of severe skeletal trauma or orthopedic procedures from pulmonary micro-vessel blockage by bone marrow fat. Vascular obstruction and bone marrow necrosis occur in PFE and ACS.  Pulmonary fat embolism rat models have shown that angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB) mitigate damage in PFE. These medications could work similarly in ACS. We hypothesize that time to readmission after one hospitalization for ACS will be reduced in patients taking ACEI or ARB compared to patients who are not. Methods This is a retrospective cohort study. Inclusion criteria are adults (18 to 100 years) with sickle cell anaemia (HbSS), hemoglobin SC (HbSC) disease, sickle cell thalassemia (HbSßThal), hospitalized with ACS over 16 years (January 1, 2000, to March 31, 2016); patients who take and don't take ACEI or ARB. Children (<18 years old), elderly adults (>100 years old), pregnant patients, and patients with sickle cell trait were excluded. Data was collected from the Health Facts database, which contains de-identified information from the electronic medical records of hospitals in which Cerner© has a data use agreement. Kaplan-Meier estimates explored a time-to-event model of ACS readmission. Multivariable analysis (age, gender, smoking history) was conducted using Cox proportional hazards regression. Results were reported around a 95% confidence interval. Results There were 6972 patients in total. Of which, 9.6% (n = 667) reported taking ACEI or ARB. Results for the covariates were: average age of 38 years old; 63% female (n = 4366/6969); 16% smokers (n = 1132). Readmission rates were higher for patients not taking ACEI/ARB than those who did: 0.44 (95% CI 0.43, 0.46) versus 0.28 (95% CI 0.24, 0.31) at one year, and 0.56 (95% CI 0.55, 0.58) versus 0.33 (95% CI 0.29, 0.37) at two years. Age had the strongest effect on readmission rates for patients taking ACEI/ARB (adjusted hazards ratio 0.78 [95% CI 0.68, 0.91]). Conclusion Patients with SCD who reported taking ACEI or ARB had lower readmission rates for ACS; age was the strongest covariate. Our results may have a significant impact on the prevention of ACS. Prospective studies comparing ACEI or ARB therapy versus placebo are needed to confirm this preventative effect.

Cod Liver Oil, but Not Retinoic Acid, Treatment Restores Bone Thickness in a Vitamin A-Deficient Rat.

Vitamin A plays a prominent role for maintaining optimal bone status, but its impact upon the bone in response to vitamin A deficiency is not well defined. The purpose of this study was to evaluate how replenishing vitamin A by either whole food cod liver oil (COD) or the active metabolite of vitamin A, retinoic acid (RA), altered bone thickness of vitamin A-deficient (VAD) rats. Weanling rats were administered a control diet (CTRL) or VAD diet for 9 weeks. This was followed by four weeks of treatment in which the VAD group was divided into the following 4 subgroups: (1) VAD (9 weeks)-VAD (4 weeks); (2) VAD-CTRL; (3) VAD-COD; and (4) VAD-RA. Compared to controls, VAD rats had thicker bones which showed marked dysplasia. VAD-rats treated with COD produced a thinner bone that was not significantly different from that of untreated rats. In contrast, RA did not significantly change the thicker bone, and also had significantly greater periosteal and endosteal osteoblast numbers compared to VAD-COD. Active osteoclasts were not detected in VAD rats, nor during the treatment period. These findings suggest that the abnormal bone thickness in VAD rats appears to be more effectively restored to bone thickness of untreated control rats when treated with COD.

Preclinical Safety Evaluation of HIV-1 gp120 Responsive Microbicide Delivery System in C57BL/6 Female Mice.

Many novel vaginal/rectal microbicide formulations failed clinically due to safety concerns, indicating the need for the early investigation of lead microbicide formulations. In this study, the preclinical safety of an HIV-1 gp120 and mannose responsive microbicide delivery system (MRP) is evaluated in C57BL/6 mice. MRP was engineered through the layer-by-layer coating of calcium carbonate (CaCO3) with Canavalia ensiformis lectin (Con A) and glycogen. MRP mean particle diameter and zeta potential were 857.8 ± 93.1 nm and 2.37 ± 4.12 mV, respectively. Tenofovir (TFV) encapsulation and loading efficiencies in MRP were 70.1% and 16.3% w/w, respectively. When exposed to HIV-1 rgp120 (25 µg/mL), MRP released a significant amount of TFV (∼5-fold higher) in vaginal and seminal fluid mixture compared to the control (pre-exposure) level (∼59 µg/mL) in vaginal fluid alone. Unlike the positive control treated groups (e.g., nonoxynol-9), no significant histological damages and CD45+ cells infiltration were observed in the vaginal and major reproductive organ epithelial layers. This was probably due to MRP biocompatibility and its isosmolality (304.33 ± 0.58 mOsm/kg). Furthermore, compared to negative controls, there was no statistically significant increase in pro-inflammatory cytokines such as IL1α, Ilß, IL7, IP10, and TNFα. Collectively, these data suggest that MRP is a relatively safe nanotemplate for HIV-1 gp120 stimuli responsive vaginal microbicide delivery system.

Evidence for angiotensin mediation of the late histopathological effects of pulmonary fat embolism: Protection by losartan in a rat model.

PURPOSE: In a model of fat embolism using triolein-treated rats, we have reported that the acute pulmonary histopathological changes at 48 hrs were ameliorated by the angiotensin AT1 receptor blocker losartan, the angiotensin converting enzyme inhibitor captopril, and the direct renin inhibitor aliskiren. Although much of the pathology had declined by 3 weeks, the changes persisted at 6 weeks. The purpose of the study was to extends the time course investigation to 10 weeks and to examines whether the fat embolism effects continue to be blocked by losartan when given at a late time period. MATERIALS AND METHODS: Unanesthetized rats were challenged with i.v. triolein or saline. After 6 weeks, one group received saline or losartan i.p. and the losartan group also received losartan in the drinking water. At 10 weeks, the experiment was terminated. RESULTS: Confirming previous results, the fat embolism group showed normal weight gain at 6 weeks without apparent distress and also appeared normal at 10 weeks. However, at 10 weeks the lungs showed inflammatory and fibrotic changes that were greater than those found at 6 weeks. These changes were reduced by losartan. CONCLUSIONS: These findings show that the effects of fat embolism continue to progress to 10 weeks after the initial insult with triolein. The fact that the protective effects of losartan treatment started at 6 weeks supports the involvement of the renin-angiotensin system in late as well as early stages of the histopathological changes following fat embolism. It also supports the use of angiotensin blockade in clinical situations even long after an initial trauma where fat embolism is suspected.

Spray-Dried Thiolated Chitosan-Coated Sodium Alginate Multilayer Microparticles for Vaginal HIV Microbicide Delivery.

It is hypothesized that novel thiolated chitosan-coated multilayer microparticles (MPs) with enhanced drug loading are more mucoadhesive than uncoated MPs and safe in vivo for vaginal delivery of topical anti-HIV microbicide. Formulation optimization is achieved through a custom experimental design and the alginate (AG) MPs cores are prepared using the spray drying method. The optimal MPs are then coated with the thiolated chitosan (TCS) using a layer-by-layer method. The morphological analysis, in situ drug payload, in vitro drug release profile, and mucoadhesion potential of the MPs are carried out using scanning electron microscopy, solid-state 31P NMR spectroscopy, UV spectroscopy, fluorescence imaging and periodic acid Schiff method, respectively. The cytotoxicity and preclinical safety of MPs are assessed on human vaginal (VK2/E6E7) and endocervical (End1/E6E7) epithelial cell lines and in female C57BL/6 mice, respectively. The results show that the MPs are successfully formulated with an average diameter ranging from 2 to 3 µm with a drug loading of 7-12% w/w. The drug release profile of these MPs primarily follows the Baker-Lonsdale and Korsmeyer-Peppas models. The MPs exhibit high mucoadhesion (20-50 folds) compared to native AGMPs. The multilayer MPs are noncytotoxic. Histological and immunochemical analysis of the mice genital tract shows neither signs of damage nor inflammatory cell infiltrate. These data highlight the potential use of TCS-coated AG-based multilayer MPs templates for the topical vaginal delivery of anti-HIV/AIDS microbicides.

The renin inhibitor aliskiren protects rat lungs from the histopathologic effects of fat embolism.

BACKGROUND: Fat embolism (FE) and the consequent FE syndrome occurring after trauma or surgery can lead to serious pulmonary injury, including ARDS and death. Current treatment of FE syndrome is limited to supportive therapy. We have shown in a rat model that the renin angiotensin system plays a significant role in the pathophysiology of FE because drugs interfering with the renin angiotensin system, captopril and losartan reduce the histopathologic pulmonary damage. The purpose of the current study was to determine if inhibition of renin by aliskiren, an FDA-approved drug for treating hypertension, would produce effective protection in the same model. METHODS: The FE model used intravenous injection of the neutral fat triolein in unanesthetized rats. Intraperitoneal injections of saline or aliskiren at either 50 or 100 mg/kg were performed 1 hour after FE induction via triolein. Rats were euthanized at 48 hours, and various histologic stains were used to examine the lungs. RESULTS: (1) Fibrosis: rats treated with triolein showed significant fibrotic changes with increased collagen and myofibroblast activation (p < 0.0001 for both trichrome and α-smooth muscle actin staining). Aliskiren blocked this inflammatory and profibrotic process to a level indistinguishable from the controls (p < 0.0001 for both trichrome and α-smooth muscle actin staining). (2) Fat: rats treated with triolein showed a statistically significant increase in fat (p = 0.0006). Subsequent aliskiren administration at both doses reduced the size, distribution, and amount of fat droplets (low dose, p = 0.0095; high dose, p = 0.0028). (3) Vessel patency: the low dose of aliskiren blocked the reduction of lumen patency observed after triolein administration (p = 0.0058). CONCLUSIONS: Aliskiren protected the lungs of rats from gross and histopathologic FE-induced pulmonary damage at 48 hours. Clinical implications include the use of aliskiren both prophylactically (before certain orthopedic procedures) and therapeutically (after severe trauma) to prevent the consequent severe pulmonary pathologic sequelae.

Stimuli-sensitive thiolated hyaluronic acid based nanofibers: synthesis, preclinical safety and in vitro anti-HIV activity.

AIM: To develop a seminal enzyme bioresponsive, mucoadhesive nanofibers (NFs) as safe and effective nanocarriers for the prevention of HIV vaginal transmission. METHODS: A novel thiolated hyaluronic acid (HA-SH) polymer was synthesized to fabricate tenofovir (TFV)-loaded electrospun NFs (HA-SH-NFs) and characterized in vitro/in vivo. RESULTS: A triggered drug release (87% w/w) from the engineered HA-SH-NFs (mean diameter ∼75 nm) occured within 1 h under the influence of seminal hyaluronidase enzyme. HA-SH-NFs were noncytotoxic, induced no damage on the C57BL/6 mice genital-tract and other organs. No significant CD45 cell-infiltration and changes in cytokines level in cervicovaginal tissues were observed. HA-SH-NFs significantly enhanced both TFV retention and bioavailability in vaginal tissue compared with the 1% TFV-gel. The anti-HIV activity of TFV (on pseudotyped virus followed by luciferase assay) was not adversely affected by the electrospinning process. CONCLUSION: HA-SH-NFs developed in this study could potentially serve as a safe nanotemplate for topical intravaginal delivery of HIV/AIDS microbicides.

Tenofovir Containing Thiolated Chitosan Core/Shell Nanofibers: In Vitro and in Vivo Evaluations.

It is hypothesized that thiolated chitosan (TCS) core/shell nanofibers (NFs) can enhance the drug loading of tenofovir, a model low molecular weight and highly water-soluble drug molecule, and improve its mucoadhesivity and in vivo safety. To test this hypothesis, poly(ethylene oxide) (PEO) core with TCS and polylactic acid (PLA) shell NFs are fabricated by a coaxial electrospinning technique. The morphology, drug loading, drug release profiles, cytotoxicity and mucoadhesion of the NFs are analyzed using scanning and transmission electron microscopies, liquid chromatography, cytotoxicity assays on VK2/E6E7 and End1/E6E7 cell lines and Lactobacilli crispatus, fluorescence imaging and periodic acid colorimetric method, respectively. In vivo safety studies are performed in C57BL/6 mice followed by H&E and immunohistochemical (CD45) staining analysis of genital tract. The mean diameters of PEO, PEO/TCS, and PEO/TCS-PLA NFs are 118.56, 9.95, and 99.53 nm, respectively. The NFs exhibit smooth surface. The drug loading (13%-25%, w/w) increased by 10-fold compared to a nanoparticle formulation due to the application of the electrospinning technique. The NFs are noncytotoxic at the concentration of 1 mg/mL. The PEO/TCS-PLA core/shell NFs mostly exhibit a release kinetic following Weibull model (r2 = 0.9914), indicating the drug release from a matrix system. The core/shell NFs are 40-60-fold more bioadhesive than the pure PEO based NFs. The NFs are nontoxic and noninflammatory in vivo after daily treatment for up to 7 days. Owing to their enhanced drug loading and preliminary safety profile, the TCS core/shell NFs are promising candidates for the topical delivery of HIV/AIDS microbicides such as tenofovir.

Fat embolism sensitizes rats to a "second hit" with lipopolysaccharide: An animal model of pulmonary fibrosis.

BACKGROUND: Pulmonary fat embolism (FE) in patients after major bone fracture and other trauma may lead to acute respiratory distress, but few clinical evidence of lung injury remains, and there is a dearth of histopathologic information after the initial recovery. We recently reported histologic changes in the lungs of a patient who died after cesarian delivery, which were similar to a rat model of FE. In this model, we found that despite an apparent full recovery, modest fibrotic damage persisted up to 6 weeks. We tested whether at that time, an additional insult could exacerbate the effects. METHODS: Triolein (0.2 mL intravenously administered) was given to 18 rats and saline to 18 controls. Six weeks later, each group received (intraperitoneal) lipopolysaccharide (LPS, 3 mg/kg; n = 9) or saline (n = 9). At necropsy 48 hours later, lungs and organs were harvested for study. Lung parenchymal, vascular, and bronchial damage was scored by two pathologists and by Image J analysis. RESULTS: Animals given LPS after triolein showed reduced pulmonary arterial medial diameters compared with those that received LPS alone (p < 0.04). Lung small arterial patency (lumen) was reduced after triolein and even more after combined LPS and triolein (p = 0.018). Triolein increased fibrotic markers (trichrome and smooth muscle actin staining), and this was more severe after LPS. At 6 weeks, fat droplets remained in the lungs, localizing to the subpleural septa. These were smaller and more widespread after LPS. CONCLUSION: This report describes an animal model to study exacerbation of lung histopathology induced by FE using a known pulmonary toxicant, LPS (a "second hit"). Vascular and fibrotic lung damage was more severe when LPS was given to rats 6 weeks after triolein compared with LPS alone. FE rendered the lungs extra sensitive to a second hit long after apparent clinical recovery. This experimental model of fat embolism provides useful informations for the treatment of patients suffering for similar conditions.

Dietary Flaxseed Oil Protects against Bleomycin-Induced Pulmonary Fibrosis in Rats.

Bleomycin, a widely used antineoplastic agent, has been associated with severe pulmonary toxicity, primarily fibrosis. Previous work has shown a reduction in bleomycin-induced lung pathology by long-chain omega-3 fatty acids. Treatment by short-chain omega-3 fatty acids, α-linolenic acid, found in dietary flaxseed oil may also reduce lung fibrosis, as previously evidenced in the kidney. To test this hypothesis, 72 rats were divided between diets receiving either 15% (w/w) flaxseed oil or 15% (w/w) corn oil (control). These groups were further divided to receive either bleomycin or vehicle (saline) via an oropharyngeal delivery, rather than the traditional intratracheal instillation. Lungs were harvested at 2, 7, and 21 days after bleomycin or saline treatment. Animals receiving flaxseed oil showed a delay in edema formation (P = 0.025) and a decrease in inflammatory cell infiltrate and vasculitis (P = 0.04 and 0.007, resp.). At days 7 and 21, bleomycin produced a reduction in pulmonary arterial lumen patency (P = 0.01), but not in rats that were treated with flaxseed oil. Bleomycin-treated rats receiving flaxseed oil had reduced pulmonary septal thickness (P = 0.01), signifying decreased fibrosis. Dietary flaxseed oil may prove beneficial against the side effects of this highly effective chemotherapeutic agent and its known toxic effects on the lung.

Effect of exendin (exenatide)--GLP 1 receptor agonist on the thyroid and parathyroid gland in a rat model.

Exenatide or Exendin-4 is a 39-amino acid agonist of the glucagon like peptide (GLP-1) receptor approved for the adjunctive treatment for type 2 diabetes. Recent reports suggest that GLP-1 agonists may also have distant effects including C-cell thyroid hyperplasia. The aim of this study was to evaluate the effect of exendin-4 on the thyroid and parathyroid cells in a rat model. Rat thyroids were stained for calcitonin, H&E and for carcinoembryonic antigen (CEA). Thyroid C-cell hyperplasia was graded on H&E stained slides using cell size and secretory granule numbers, morphological features of the parathyroid glands and the serum calcium concentrations of the rats were also evaluated. Counts of stained cells/high power field and intensity of staining were recorded by two pathologists. Data were analyzed by ANOVA/post-tests. C cell hypertrophy was elevated in exenatide-treated vs. untreated animals (22.5 ± 8.7 vs. 10.5 ± 2.7 cells/HPF). CEA staining failed to show effects by exendin. Calcitonin staining was significantly elevated in exenatide treated controls (P<0.001). Parathyroid glands were histologically normal in both groups, and serum calcium levels were within normal range in all animals. In summary, exenatide was associated with C cell hyperplasia and increased calcitonin staining of thyroids, but was unrelated to CEA levels. These data raise important concerns about the effects of exenatide which, given its wide clinical use, should be clarified with urgency.

Persistent and progressive pulmonary fibrotic changes in a model of fat embolism.

BACKGROUND: Fat embolism (FE) after trauma and some orthopedic procedures is known to cause acute lung injury, including acute respiratory distress syndrome. However, its potential long-term effects on the lung are unknown. A previous study using a rat model of FE found significant histopathologic changes in the lungs after intravenous injection of triolein for up to 11 days. This study detailed the persistence of the lung damage and investigated the input of the renin-angiotensin system in its pathology. METHODS: Unanesthetized rats were injected via the tail vein with 0.2 mL saline or triolein. After euthanasia, at 3 weeks or 6 weeks, lung sections were stained to highlight cellular structure, presence of collagen and fat, or immunolabeled for smooth muscle actin or angiotensin peptides. RESULTS: At 3 weeks or 6 weeks after triolein injection, there was no dilatation of the heart or inferior vena cava, no congestion of the liver or spleen, no adventitial edema, nor was fluid present in alveoli or pleural cavity as reported in animals at earlier time points. Persisting pathology included reduced lumen patency, thickening of the media of small arteries and arterioles, and vascular and septal inflammation. Although the fat content of the lung decreased from week 3 to week 6, there was a progressive increase in collagen, smooth muscle actin, and angiotensin peptides. CONCLUSIONS: This model extends the effect of FE on pulmonary pathology to 6 weeks, revealing persistent vasculitis, septal inflammation, and progressive fibrotic changes which are associated with increased presence of angiotensin peptides.

Mitigating effects of captopril and losartan on lung histopathology in a rat model of fat embolism.

BACKGROUND: Fat embolization (FE) is an often overlooked and poorly understood complication of skeletal trauma and some orthopedic procedures. Fat embolism can lead to major pulmonary damage associated with fat embolism syndrome (FES). METHODS: A model of FE in unanesthetized rats, using intravenous injection of the neutral fat triolein, was used to study the potential therapeutic effect on lung histopathology of altering the production of, or response to, endogenous angiotensin (Ang) II. Either captopril, an Ang I converting enzyme inhibitor, or losartan, an Ang II type 1 receptor blocker, was injected 1 hour after FE by triolein injection. After euthanasia at 48 hours, histopathologic evaluation was used to compare the drug-treated animals with control animals that received only triolein. RESULTS: Histology of the lungs of rats treated only with triolein revealed severe, diffuse pathology. Alveolar septa showed severe, diffuse inflammation. Bronchial lumina showed severe mucosal epithelial loss. The media of the pulmonary small arteries and arterioles was thicker, and the lumen patency was reduced 60% to 70%. Trichrome staining confirmed the abundant presence of collagen in the media and adventitia, as well as collagen infiltrating the bronchial musculature. Both captopril and losartan treatments reduced the inflammatory, vasoconstrictor, and profibrotic effects present at 48 hours (p<0.001). With treatment, the vascular lumen remained patent, and the fat droplets were reduced in size and number. There was a reduction in the number of infiltrating leukocytes, macrophages, myofibroblasts, and eosinophils, along with a significant decrease in hemorrhage and collagen deposition (p<0.001). Pathologic changes in bronchial epithelium were also diminished. CONCLUSIONS: The results suggest that the use of drugs that act on the renin-Ang system might provide an effective and targeted therapy for fat embolism syndrome.

Treatment with omega-3 fatty acids but not exendin-4 improves hepatic steatosis.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in the Western world. The aim of this study was to evaluate the biochemical and histological effects of omega-3 fatty acid and exendin-4 treatment on NAFLD in an animal model. METHODS: Sixty-three 8-week-old outbred Sprague-Dawley male rats were used for this study. Three animals were used as procedure controls, and 30 rats were fed a methionine and choline deficient (MCD) diet and 30 were fed a regular chow diet. In each group of 30 animals, 10 served as controls, 10 received exendin-4, and 10 received omega-3 fatty acids. After 75 days of treatment, the animals were euthanized, the tissues and serum were harvested, and the livers were formalin-fixed for histology. RESULTS: The MCD diet was exceptionally efficient at producing fatty livers. The MCD control animals had a liver steatosis score of 38+/-6.7 (of 50 possible); treatment with exendin-4 was not associated with a significant reduction of steatosis (44+/-5.16, P=0.07) and the omega-3 fatty acid treatment was associated with a significant decrease in the liver steatosis score (15.6+/-13.46, P<0.001) compared with both the controls and the exendin-4 groups. The omega-3 fatty acid treatment increased serum aspartate aminotransferase significantly, whereas exendin-4 had no effect. CONCLUSION: In an animal model of NAFLD, the omega-3 fatty acid therapy was associated with significant improvement in hepatic steatosis compared with exendin-4. These data suggest that omega-3 fatty acid supplements may have a potential therapeutic role in patients with NAFLD.

Fat embolism: evolution of histopathological changes in the rat lung.

The pathophysiology of Fat Embolism Syndrome (FES) is poorly understood and subject to some controversy. Evaluation of the evolution of histological changes in the lungs of patients with FES is impractical. The current theories of FES were established through acute clinical observations and acute animal experiments, but sequential changes in the histology of lungs over a prolonged period have not been made. The progressive effects of fat embolization of the lungs were examined in a rat model over a period of 11 days. Triolein, a major bone marrow fat, was administered to conscious Sprague-Dawley rats via the caudal vein. Rats were euthanized at 24, 48, 96 h, and 11 days, but some died within a few hours. Histomorphometric evaluations of lung tissue were made, including stains for fat, collagen, and smooth muscle actin. Arterial and arteriolar patency decreased progressively up to 96 h, but returned toward normal after 11 days. A striking finding was the very early presence of inflammation and fibrosis after only several hours, persisting up to 11 days. The results of this study provide evidence of both very early and prolonged changes due to fat embolization.

Effects of dietary calorie restriction or exercise on the PI3K and Ras signaling pathways in the skin of mice.

Weight control by exercise and dietary calorie restriction (DCR) has been associated with reduced cancer risk, but the underlying mechanisms are not well understood. This study was designed to compare the effects of weight loss by increasing physical activity or decreasing calorie intake on tumor promoter-induced Ras-MAPK and PI3K-Akt pathways. SENCAR mice were randomly assigned to one of the following five groups: ad libitum-fed sedentary control, ad libitum-fed exercise (AL+Exe), exercise but pair-fed at the amount as controls (PF+Exe), 20% DCR, and 20% DCR plus exercise (DCR+Exe). After 10 weeks, body weight and body fat significantly decreased in the groups of DCR, DCR+Exe, and PF+Exe when compared with the controls. AL+Exe did not induce weight loss due to, at least in part, increased food intake. Plasma IGF-1 levels reduced significantly in DCR and DCR+Exe but not PF+Exe. The protein H-Ras and activated Ras-GTP significantly decreased in TPA-induced skin tissues of DCR-fed mice but not exercised mice. PI3K protein, phosphoserine Akt, and p42/p44-MAPK were reduced, however, in both DCR and PF+Exe groups. Immunohistochemistry demonstrated that the significantly reduced H-Ras occurred in subcutaneous fat cells, while the reduced PI3K and PCNA took place only in the epidermis. Plasma leptin decreased in PF+Exe, DCR, and DCR+Exe, while the caspase-3 activity increased in DCR+Exe only. Genomic microarray analysis further indicated that the expression of 34 genes relevant to PI3K and 31 genes to the MAPK pathway were significantly regulated by either DCR or PF+Exe treatments. The reduced PI3K in PF+Exe mice was partially reversed by IGF-1 treatment. The overall results of this study demonstrated that DCR abrogated both Ras and PI3K signaling, which might inhibit TPA-induced proliferation and anti-apoptosis. Selective inhibition of PI3K by PF+Exe but not AL+Exe seems more attributable to the magnitude of the caloric deficit and/or body fat loss than diet versus exercise comparison.

Effect of an angiotensin II receptor blocker and two angiotensin converting enzyme inhibitors on transforming growth factor-beta (TGF-beta) and alpha-actomyosin (alpha SMA), important mediators of radiation-induced pneumopathy and lung fibrosis.

Progressive, irreversible fibrosis is one of the most clinically significant consequences of ionizing radiation on normal tissue. When applied to lungs, it leads to a complication described as idiopathic pneumonia syndrome (IPS) and eventually to organ fibrosis. For its high mortality, the condition precludes treatment with high doses of radiation. There is widespread interest to understand the pathogenetic mechanisms of IPS and to find drugs effective in the prevention of its development. This report summarizes our experience with the protective effects of L 158,809, an angiotensin II (ANG II) receptor blocker, and two angiotensin converting enzyme (ACE) inhibitors in the development of IPS and the role of transforming growth factor beta (TGF-beta) and of alpha-actomyosin (alpha SMA) in pathogenesis of radiation induced pulmonary fibrosis in an experimental model of bone marrow transplant (BMT). Male WAG/Riji/MCV rats received total body irradiation and a regimen of cyclophosphamide (CTX) in preparation for bone marrow transplant. While one group of animals remained untreated, the remainders were subdivided into three groups, each of them receiving either the ANG II receptor blocker or one of the two ACE inhibitors (Captopril or Enalapril). Each of the three drugs was administered orally from 11 days before the transplant up to 56 days post transplant. At sacrifice time the irradiated rats receiving only CTX showed a chronic pneumonitis with septal fibrosis and vasculitis affecting, in particular, small caliber pulmonary arteries and arterioles. Their lung content of hydroxyproline was also markedly elevated in association with the lung concentrations of thromboxane (TXA2) and prostaglandin (PGI(2)), (two markers of pulmonary endothelial damage). A significant increase of alpha actomyosin staining was observed in vessels, septa and macrophages of the same animals which also overexpressed TGF-beta. When L 158,809, Captopril and Enalapril were added to the radiation and cytoxan treatment, a significant amelioration of the histological damage as well as the overexpression of alpha SMA was observed. Lung concentrations of hydroxyproline, PGI(2), TXA2 and TGF-beta were also observed in these animals so that the values of these compounds were closer to those measured in untreated control rats than to their irradiated and cytoxan treated counterparts. Angiotensin II plays an important role in the regulation of TGF-beta and alpha SMA, two proteins involved in the pathogenesis of pulmonary fibrosis. The finding that ACE inhibitors or ANG II receptor blockers protect the lungs from radiation induced pneumonitis and fibrosis reaffirms the role that ANG II plays in this inflammatory process and suggests an additional indication of treatment of this condition, thus opening a new potential pharmacologic use of these drugs.

Effects on cytokines and histology by treatment with the ACE inhibitor captopril and the antioxidant retinoic acid in the monocrotaline model of experimentally induced lung fibrosis.

Monocrotaline (MCT), a pyrrolizidine alkaloid extracted from the shrub Crotalaria spectabilis, induces in the lungs of many mammalian species severe hypertension and fibrosis. Previous work with MCT-induced lung disease in rats has shown that some of the steps to progressive fibrosis can be interrupted or decreased by intervention with retinoic acid (RA) or with the angiotensin converting enzyme inhibitor, captopril. This report emphasizes the pathology and cytokines present in lungs of rats in the MCT model of hypertension and fibrosis in 8 treatment groups, six per group: (1) controls, not treated; (2) captopril; (3) RA; (4) combined captopril and RA. Groups 5-8 replicated groups 1-4 and also received MCT subcutaneously. Tissues were harvested at 28 days for histopathology and measurement of cytokines TGFbeta, TNFalpha, interleukin 6, and IFN_. TGFbeta was depressed at 28 days by MCT, an effect reversed by a combination of captopril and RA. RA influences production of an important Th1 cytokine, IFN_, and demonstrated the greatest limitation of MCT-induced TNFalpha. The MCT-induced lung pathology of vasculitis, interstitial pneumonia and fibrosis was limited by captopril. Smooth muscle actin was overexpressed in MCT treated animals receiving RA, an effect reduced with captopril. Overall, the study confirmed the existence of a protective effect for both captopril and RA from MCT-induced lung damage at 30 days. No synergistic or antagonistic activity was observed when the two drugs were administered together. Each of the drugs exerts different and particular effects on serum and tissue levels of various cytokines, suggesting that each drug is efficient at different points of attack in the control of lung fibrosis.

Vitamin A and emphysema.

Within the last several years, research scientists and clinicians have been intrigued with the potential use of an active form of vitamin A, retinoic acid (RA), for the treatment and prevention of emphysema. The interest in this area can be largely attributed to the work of Massaro and Massaro (1996, 1997, 2000) in which they presented evidence that RA partially protects against and to some degree restores elastase-induced emphysema in rats. The mechanism for this protective effect of RA is in part related to elastin metabolism. RA also inhibits inflammation, an upstream event that may lead to the development of emphysema. Although there is evidence of this protective effect in young rats and a mechanistic explanation, more studies are needed in humans in order to establish a role for vitamin A in protecting against emphysema. Too many unanswered questions remain to definitively state that vitamin A protects against this disease in humans. Nevertheless, the potential for this novel approach in prevention and treatment of emphysema is an exciting area of research.