¹H and hyperpolarized ³He magnetic resonance imaging clearly detect the preventative effect of a glucocorticoid on endotoxin-induced pulmonary inflammation in vivo.

INTRODUCTION: Proton (¹H ) magnetic resonance imaging (MRI) can be utilized to quantify pulmonary edema in endotoxin-induced pulmonary inflammation and hyperpolarized (HP) ³He MRI can assess pulmonary ventilation. Neither of the methods has been applied to assess the impact of a drug on endotoxin-induced pulmonary inflammation in vivo. The aim of the current study was to evaluate the capability of ¹H and HP ³He MRI to assess the effects of a glucocorticoid on endotoxin-induced pulmonary inflammation in vivo. MATERIALS AND METHODS: Mice were exposed to an aerosol of either saline or endotoxin (5 mg/ml) for 10 min. Half of the endotoxin-exposed mice were pretreated with a glucocorticoid (budesonide 3 mg/kg; 2 times/day) and the other half with vehicle p.o. The first budesonide treatment was administered 1 h prior to the aerosol inhalation. Forty-eight hours after the aerosol exposure, the mice were anaesthetized for subsequent imaging. Hyperpolarized ³He was administered and axial MR images of the lungs obtained. Matching ¹H MR images were then acquired. The mice were sacrificed and broncho-alveolar lavage (BAL) samples were harvested to determine total and cell differential counts. RESULTS: The lesion volume on both ¹H and ³He MRI, were markedly increased by endotoxin exposure (P<0.001). Budesonide strongly reduced lesion volume (P<0.001). The BAL cell count correlated strongly with both (3)He (P<0.001; r = 0.96) and ¹H lesion volumes (P<0.001; r = 0.97). CONCLUSIONS: Hyperpolarized ³He MRI and ¹H MRI clearly visualized the preventative effect of budesonide on the impact of endotoxin on pulmonary ventilation and edema, respectively. The fact that ventilation defects on ³He MRI corresponded to findings from conventional ¹H MRI, as well as to counts of BAL inflammatory cells suggests that these imaging techniques constitute promising tools for non-invasive monitoring of pulmonary inflammation in vivo.

The role of the CCR1 receptor in the inflammatory response to tobacco smoke in a mouse model.

OBJECTIVE: The aim was to create pathological changes in mice relevant to human smoke exposure that can be used to further understand the mechanisms and pathology of smoke-induced inflammatory disease. METHODS: Mice were exposed to tobacco smoke or lipopolysaccharide (LPS) to generate an inflammatory infiltrate within the lungs. RESULTS: Tobacco smoke exposure over a 4 day period led to neutrophilia in the lungs of BALB/c mice. Within the inflammatory exudates, significant changes were also seen in protein levels of IL-1B, IL-6, MIP-2, KC (IL-8) and TIMP-1 as measured by ELISA. Further protein changes, as measured via multiplex analysis revealed increased levels of MMP-9, MDC, LIF and MCP-1, amongst other mediators. Major changes in whole lung tissue gene expression patterns were observed. The neutrophilia seen after smoke exposure was steroid-insensitive, relative to doses of steroid needed to reduce LPS-driven neutrophilia in controls. This exposes pathological switches that are changed upon exposure to tobacco smoke, rendering steroids less effective under these conditions. Challenge of chemokine receptor type 1 (CCR1) KO mice in the tobacco smoke model showed that lack of this gene protected the mice from smoke-induced inflammation. CONCLUSIONS: This suggests the CCR1 receptor has a key role in the pathogenesis of smoke-induced inflammation.

(1)H and hyperpolarized (3)He MR imaging of mouse with LPS-induced inflammation.

PURPOSE: To evaluate the lipopolysaccharide (LPS) model of chronic obstructive pulmonary disease (COPD) in mouse with (1)H and hyperpolarized (HP) (3)He MR imaging. MATERIALS AND METHODS: Axial slices of the lung volume were acquired with HP (3)He and (1)H MRI at 4, 24, and 48 h after LPS exposure. A quantitative ventilation index was calculated from two HP (3)He acquisitions. A bronchoalveolar lavage (BAL) for a cell count was performed following magnetic resonance imaging (MRI). RESULTS: The LPS exposure resulted in a significant increase of cells in BAL, with maximum at 48 h. Lesions on (3)He images were characterized by ventilation defects, whereas lesions on (1)H images were hyperintense and were attributed to edema. The number of lesions was at maximum at 48 h. At this time point, and for both (3)He and (1)H MRI, the volume of the lesions was significantly higher for LPS-exposed mice compared to controls. At 4, 24, and 48 h the ventilation index from the (3)He data was significantly smaller for the LPS-exposed animals compared to controls. CONCLUSION: The time point 48 h after LPS exposure was advantageous for MRI evaluation. Functional read-out with (3)He MRI seems to be more sensitive than conventional (1)H MRI.

Bacteria challenge in smoke-exposed mice exacerbates inflammation and skews the inflammatory profile.

RATIONALE: The pathogenesis of chronic obstructive pulmonary disease is associated with acute episodes of bacterial exacerbations. The most commonly isolated bacteria during episodes of exacerbation is nontypeable Haemophilus influenzae (NTHI). OBJECTIVES: In this study, we investigated the in vivo consequences of cigarette smoke exposure on the inflammatory response to an NTHI challenge. METHODS: C57BL/6 and BALB/c mice were exposed to cigarette smoke for 8 weeks and subsequently challenged intranasally with NTHI. MEASUREMENTS AND MAIN RESULTS: We observed increased pulmonary inflammation and lung damage in cigarette smoke-exposed NTHI-challenged mice as compared with control NTHI-challenged mice. Furthermore, although NTHI challenge in control mice was marked by increases in tumor necrosis factor-alpha, IL-6, MIP-2, and KC/GROalpha, NTHI challenge in cigarette smoke-exposed mice led to a prominent up-regulation of a different subset of inflammatory mediators, most notably MCP-1, -3, and -5, IP-10, and MIP-1gamma. This skewed inflammatory mediator expression was also observed after ex vivo NTHI stimulation of alveolar macrophages, signifying their importance to this altered response. Importantly, corticosteroids attenuated inflammation after NTHI challenge in both cigarette smoke-exposed and control mice; however, this was associated with significantly increased bacterial burden. CONCLUSIONS: Collectively, these data suggest that cigarette smoke exacerbates the inflammatory response to a bacterial challenge via skewed inflammatory mediator expression.

Effect of an MMP-9/MMP-12 inhibitor on smoke-induced emphysema and airway remodelling in guinea pigs.

BACKGROUND: Matrix metalloproteases (MMPs) are believed to be important in the pathogenesis of cigarette smoke-induced emphysema, but this hypothesis has only been proved in the mouse and its applicability to other species, particularly humans, is uncertain. The role of MMPs in smoke-induced small airway remodelling is unknown. METHODS: The effects of a dual MMP-9/MMP-12 inhibitor, AZ11557272, on the development of anatomical and functional changes of chronic obstructive pulmonary disease (COPD) in guinea pigs exposed daily to cigarette smoke for up to 6 months were examined. RESULTS: At all times, smoke-induced increases in lavage inflammatory cells, lavage desmosine (a marker of elastin breakdown) and serum tumour necrosis factor alpha (TNFalpha) were completely abolished by AZ11557272. At 6 months there was an increase in lung volumes and airspace size. AZ11557272 returned the pressure- volume curve to control levels, decreased smoke-induced increases in total lung capacity, residual volume and vital capacity by about 70%, and also reversed smoke-induced airspace enlargement by about 70%. There was a very strong correlation between surface to volume ratio and both lavage desmosine and serum TNFalpha levels. AZ11557272 protected against smoke-mediated increases in small airway wall thickness but did not prevent smoke-induced increases in mean pulmonary artery pressure. CONCLUSIONS: An MMP-9/MMP-12 inhibitor can substantially ameliorate morphological emphysema, small airway remodelling and the functional consequences of these lesions in a non-murine species. These findings strengthen the idea that MMPs are important mediators of the anatomical changes behind COPD in humans, and suggest that MMP-9 and MMP-12 may be potential intervention targets.

Measurement of MR signal and T2* in lung to characterize a tight skin mouse model of emphysema using single-point imaging.

PURPOSE: To evaluate whether MRI signal and T2* measurements of lung tissue acquired at ultrashort detection times (tds) can detect emphysematous changes in lungs. MATERIALS AND METHODS: MR signal intensity of in vivo mouse lungs was measured at 4.7 T at tds of 0.2 and 0.4 msec using single-point imaging (SPI). T2* was calculated from the measurements obtained at the two tds. Two groups of 8- and 30-week-old Tight Skin (TS) and aged-matched CB57BL/6 mice were examined. The TS mice spontaneously developed emphysema-like alveolar enlargement. In vivo micro-computed tomography (microCT) scanning and histology were used as reference methods. RESULTS: MR signal and T2* were significantly lower in the lungs of TS mice than in controls. There were no significant differences between the different age groups. MR signal in lung parenchyma correlated linearly (P < 0.0001, r = 0.89) with microCT mass density, and T2* correlated linearly (P < 0.0001, r = -0.91) with the alveoli size (mean linear intercept [MLI]). CONCLUSION: The MR signal intensity and T2* measured at short tds can be used as imaging biomarkers to characterize parenchyma density and alveolar size, respectively.

Myofibroblast accumulation correlates with the formation of fibrotic tissue in a rat air pouch model.

OBJECTIVE: The pathogenesis of arthritic joints involves cartilage degradation and pannus formation. It is well known that pannus influences the cartilage; however, the mechanism behind how the degrading cartilage interacts with pannus is not well known. To investigate this interplay, the expression of extracellular matrix (ECM) components in pannus and the degrading cartilage was analyzed. METHODS: Studies were performed using a rat air pouch model where cotton with viable or killed cartilage was implanted into 7-day-old pouches for 1-28 days. The remodeling of cartilage and the formation of tissue in the cotton was characterized histologically by quantitation of infiltrated cells. The amounts of collagen, hyaluronan, and proteoglycan were estimated. RESULTS: Implantation of homologous femoral head cartilage in cotton resulted in extensive remodeling of cartilage and formation of ECM in the cotton. In cotton without cartilage, fibroblasts and myofibroblasts were the predominant cells in the early stage of analyses. The ECM formed in cotton was of a fibrotic type, with mainly collagen and smaller amounts of proteoglycans correlating to the presence of myofibroblasts. In the cotton with cartilage, however, inflammatory cells such as neutrophils, macrophages, and lymphocytes dominated. Delayed accumulation of collagen and increased synthesis of proteoglycans occurred early in cotton with viable as well as non-viable cartilage. In later stages, the cell pattern changed and the myofibroblasts emerged together with an increasing collagen formation. CONCLUSION: The interaction between cartilage and the newly formed granulation tissue results in a faster degradation of cartilage molecules, which in turn leak into the surrounding ECM and affect the recruitment of myofibroblasts. This indicates the importance of the micromatrix.