Proteinase imbalance versus biomechanical stress in pulmonary emphysema

Surface plasmon resonance imaging biosensor for cathepsin G based on a potent inhibitor: development and applications

A specific surface plasmon resonance imaging (SPRI) array biosensor for the determination of the enzymatically active cathepsin G (CatG) has been developed. For this purpose, a specific interaction between an inhibitor immobilized onto a chip surface and CatG in an analyzed solution was used. The MARS-115 CatG peptidyl inhibitor containing the 1-aminoalkylphosphonate diaryl ester moiety at the C terminus and N-succinamide with a free carboxylic function was synthesized and covalently immobilized onto the gold chip surface via the thiol group (cysteamine). Atomic force microscopy was used for the observation of surface changes during the subsequent steps of chip manufacture. Optimal detection conditions were chosen. High specificity of synthesized inhibitor to CatG was proved. The precision, as well as the accuracy, was found to be well suited to enzyme determination. The sensor application for the determination of CatG in white blood cells and saliva was shown for potential diagnosis of leukemia and oral cavity diseases during the early stages of those pathological states.

Mechanical failure, stress redistribution, elastase activity and binding site availability on elastin during the progression of emphysema

Emphysema is a disease of the lung parenchyma with progressive alveolar tissue destruction that leads to peripheral airspace enlargement. In this review, we discuss how mechanical forces can contribute to disease progression at various length scales. Airspace enlargement requires mechanical failure of alveolar walls. Because the lung tissue is under a pre-existing tensile stress, called prestress, the failure of a single wall results in a redistribution of the local prestress. During this process, the prestress increases on neighboring alveolar walls which in turn increases the probability that these walls also undergo mechanical failure. There are several mechanisms that can contribute to this increased probability: exceeding the failure threshold of the ECM, triggering local mechanotransduction to release enzymes, altering enzymatic reactions on ECM molecules. Next, we specifically discuss recent findings that stretching of elastin induces an increase in the binding off rate of elastase to elastin as well as unfolds hidden binding sites along the fiber. We argue that these events can initiate a positive feedback loop which generates slow avalanches of breakdown that eventually give rise to the relentless progression of emphysema. We propose that combining modeling at various length scales with corresponding biological assays, imaging and mechanics data will provide new insight into the progressive nature of emphysema. Such approaches will have the potential to contribute to resolving many of the outstanding issues which in turn may lead to the amelioration or perhaps the treatment of emphysema in the future.

Long-term exposure to cigarette smoke impairs lung function and increases HMGB-1 expression in mice

Cigarette smoke (CS)-induced emphysema is caused by a continuous inflammatory response in the lower respiratory tract. The development of the condition is believed to be mediated by oxidant-antioxidant imbalance. This paper describes the effects of long-term CS exposure on alveolar cell recruitment, antioxidant defense systems, activity of extracellular matrix metalloelastases, expression of metalloelastase MMP-12, and high mobility group box-1 protein (HMGB-1). Ten C57Bl/6 mice were exposed to 12 cigarettes-a-day for 60 consecutive days, while 10 control animals were exposed to ambient air. After sacrifice, bronchoalveolar lavage fluid (BALF) was removed, and lung tissue underwent biochemical and histological analyses. In CS-exposed animals influx of alveolar macrophages and neutrophils into BALF, lung static elastance, and expression of MMP-12 and HMGB-1 were significantly increased while the activity of antioxidant enzyme was significantly reduced in comparison with control group. Thus, we demonstrated for the first time that long-term CS exposure decreased antioxidant defenses concomitantly with impaired lung function, which was associated with HMGB-1 expression.

Emergent structure-function relations in emphysema and asthma

Structure-function relationships in the respiratory system are often a result of the emergence of self-organized patterns or behaviors that are characteristic of certain respiratory diseases. Proper description of such self-organized behavior requires network models that include nonlinear interactions among different parts of the system. This review focuses on 2 models that exhibit self-organized behavior: a network model of the lung parenchyma during the progression of emphysema that is driven by mechanical force-induced breakdown, and an integrative model of bronchoconstriction in asthma that describes interactions among airways within the bronchial tree. Both models suggest that the transition from normal to pathologic states is a nonlinear process that includes a tipping point beyond which interactions among the system components are reinforced by positive feedback, further promoting the progression of pathologic changes. In emphysema, the progressive destruction of tissue is irreversible, while in asthma, it is possible to recover from a severe bronchoconstriction. These concepts may have implications for pulmonary medicine. Specifically, we suggest that structure-function relationships emerging from network behavior across multiple scales should be taken into account when the efficacy of novel treatments or drug therapy is evaluated. Multiscale, computational, network models will play a major role in this endeavor.

Physiologic basis for improved pulmonary function after lung volume reduction

It is not readily apparent how pulmonary function could be improved by resecting portions of the lung in patients with emphysema. In emphysema, elevation in residual volume relative to total lung capacity reduces forced expiratory volumes, increases inspiratory effort, and impairs inspiratory muscle mechanics. Lung volume reduction surgery (LVRS) better matches the size of the lungs to the size of the thorax containing them. This restores forced expiratory volumes and the mechanical advantage of the inspiratory muscles. In patients with heterogeneous emphysema, LVRS may also allow space occupied by cysts to be reclaimed by more normal lung. Newer, bronchoscopic methods for lung volume reduction seek to achieve similar ends by causing localized atelectasis, but may be hindered by the low collateral resistance of emphysematous lung. Understanding of the mechanisms of improved function after LVRS can help select patients more likely to benefit from this approach.