Lung surfactant

Bio-Nanocarriers for Lung Cancer Management: Befriending the Barriers

Lung cancer is a complex thoracic malignancy developing consequential to aberrations in a myriad of molecular and biomolecular signaling pathways. It is one of the most lethal forms of cancers accounting to almost 1.8 million new annual incidences, bearing overall mortality to incidence ratio of 0.87. The dismal prognostic scenario at advanced stages of the disease and metastatic/resistant tumor cell populations stresses the requisite of advanced translational interdisciplinary interventions such as bionanotechnology. This review article deliberates insights and apprehensions on the recent prologue of nanobioengineering and bionanotechnology as an approach for the clinical management of lung cancer. The role of nanobioengineered (bio-nano) tools like bio-nanocarriers and nanobiodevices in secondary prophylaxis, diagnosis, therapeutics, and theranostics for lung cancer management has been discussed. Bioengineered, bioinspired, and biomimetic bio-nanotools of considerate translational value have been reviewed. Perspectives on existent oncostrategies, their critical comparison with bio-nanocarriers, and issues hampering their clinical bench side to bed transformation have also been summarized.

Effectiveness of liposomal paclitaxel against MCF-7 breast cancer cells

Paclitaxel is an effective chemotherapeutic agent that is widely used for the treatment of several cancers, including breast, ovarian, and non-small-cell lung cancer. Due to its high lipophilicity, paclitaxel is difficult to administer and requires solubilization with Cremophor EL (polyethoxylated castor oil) and ethanol, which often lead to adverse side effects, including life-threatening anaphylaxis. Incorporation of paclitaxel in dimyristoylphosphatidylcholine:dimyristoylphosphatidylglycerol (DPPC:DMPG) liposomes can facilitate its delivery to cancer cells and eliminate the adverse reactions associated with the Cremophor EL vehicle. Accordingly, the effectiveness of liposomal paclitaxel on MCF-7 breast cancer cells was examined. The results from this study showed that (i) the lipid components of the liposomal formulation were nontoxic, (ii) the cytotoxic effects of liposomal paclitaxel were improved when compared with those seen with conventional paclitaxel, and (iii) the intracellular paclitaxel levels were higher in MCF-7 cells treated with the liposomal paclitaxel formulation. The results of these studies showed that delivery of paclitaxel as a liposomal formulation could be a promising strategy for enhancing its chemotherapeutic effects.

Enzymatic determination of phosphatidylcholine, sphingomyelin and phosphatidylglycerol in lipid dispersions, blood cell membranes and rat pulmonary surfactant

A new micromethod for the determination of sphingomyelin in samples suspended in aqueous solutions, and modified micromethods for determining phosphatidylcholine and phosphatidylglycerol were used to determine phosphatidylcholine and sphingomyelin (detection limits of 1.8 mumol/l), and phosphatidylglycerol (detection limit of 2.3 mumol/l) in lipid dispersions, membranes from sheep erythrocytes and platelets, and pulmonary surfactants from rats of different ages and rats maintained under normobaric hyperoxia for 2 days prior to their sacrifice. The procedures are easy to perform, accurate, require less sample than conventional methods and can also be applied directly to aqueous samples. Phospholipase C and sphingomyelinase were used to release phosphorylcholine from phosphatidylglycerol and sphingomyelin, respectively. The choline released from phosphorylcholine by alkaline phosphatase is reconverted to phosphorylcholine by ATP and choline kinase. In the phophatidylglycerol determination, phospholipase D was used to release glycerol and phosphatidate. The glycerol formed was converted to glycerolphosphate using ATP and glycerol kinase. In all cases, the ADP thus formed was determined by following the enzymatic conversion of NADH to NAD at 340 nm in an coupled pyruvate kinase/lactate dehydrogenase system. Significant variations in the phospholipid composition of rat pulmonary surfactant were found during development; in particular there was an increase in the phosphatidylglycerol content of adult rats as compared with younger rats. Hyperoxia produced changes in the phosphatidylglycerol content of surfactant from adult rats, but not from 2-day old rats.

How far does ozone penetrate into the pulmonary air/tissue boundary before it reacts?

A simple method is suggested for calculating the time it takes ozone to traverse a biological region, such as a bilayer or a cell, and comparing this time to the halflife of ozone within that region. For a bilayer the calculations suggest that most of the ozone reacts within a bilayer, but a fraction may exit unreacted. For the lung lining fluid layer (LLFL), the calculations show that ozone cannot cross this layer without reacting where the LLFL is thicker than about 0.1 microns. However, since the LLFL varies from 20 to 0.1 microns in thickness with patchy areas in the lower airways that are virtually uncovered, some ozone could reach underlying cells, particularly in the lower airways. For cells (such as alveolar type I epithelial cells), the calculations show that ozone reacts within the cell too rapidly to pass through and exit unreacted from the other side. These calculations have implications for ozone toxicity. In vivo, the toxicity of ozone is suggested to result from the effects of a cascade of products that are produced in the reactions of ozone with primary target molecules that lie close to the air/tissue boundary. These products, which have a lower reactivity and longer lifetime than ozone itself, can transmit the effects of ozone beyond the air/tissue interface. The variation in thickness of the LLFL may modulate the species causing damage to the cells below it. In the lower airways, where the LLFL is thin and patchy, more cellular damage may be caused by ozone itself; in the upper airways where the LLFL is thicker, secondary products (such as aldehydes and hydrogen peroxide) may cause most of the damage. In vitro studies must be designed in an attempt to model the lung physiology. For example, if cells in culture are studied, and if the cells are exposed to ozone while under a supporting medium solution that contains ozone-reactive substances, then the cells may be damaged by products that are formed in the reactions of ozone with the cell medium rather than by ozone itself.

New approaches to hormonal acceleration of fetal lung maturation

The paper reviews the effects on lung maturation of glucocorticoids in animals and humans and presents relevant recent findings from the author's laboratory. It is now well established that antenatal glucocorticoid treatment reduces the incidence and severity of the respiratory distress syndrome (RDS) in prematurely born infants. The recommended doses of glucocorticoids produce fetal glucocorticoid activity levels similar to those of newborns with RDS or prolonged rupture of the membranes. Extensive follow-up studies have shown that adverse effects on child development are unlikely to occur. It is also evident that a significant number of fetuses do not respond to the treatment, which is of particular consequence in fetuses of less than 28 weeks gestation. These fetuses are less likely to respond to glucocorticoid therapy that fetuses between 28 and 32 weeks gestation and are at a higher risk of developing complications due to their immaturity. In fetal sheep, there is a similar decrease in the efficacy of glucocorticoids on lung maturation with decreasing gestational age. Simultaneous infusion of cortisol, triiodothyronine and prolactin but not of any of these hormones administered singly or in combination of two produced mature lungs in fetal sheep of 125 days gestation. Similar results were obtained with thyrotropin releasing hormone (TRH) and cortisol. It remains to be seen whether the combined administration of glucocorticoids and TRH accelerates lung maturation in human fetuses.