Insulin modulates inflammatory and repair responses to elastase-induced emphysema in diabetic rats

Mechanisms Linking COPD to Type 1 and 2 Diabetes Mellitus: Is There a Relationship between Diabetes and COPD?

Chronic obstructive pulmonary disease (COPD) patients frequently suffer from multiple comorbidities, resulting in poor outcomes for these patients. Diabetes is observed at a higher frequency in COPD patients than in the general population. Both type 1 and 2 diabetes mellitus are associated with pulmonary complications, and similar therapeutic strategies are proposed to treat these conditions. Epidemiological studies and disease models have increased our knowledge of these clinical associations. Several recent genome-wide association studies have identified positive genetic correlations between lung function and obesity, possibly due to alterations in genes linked to cell proliferation; embryo, skeletal, and tissue development; and regulation of gene expression. These studies suggest that genetic predisposition, in addition to weight gain, can influence lung function. Cigarette smoke exposure can also influence the differential methylation of CpG sites in genes linked to diabetes and COPD, and smoke-related single nucleotide polymorphisms are associated with resting heart rate and coronary artery disease. Despite the vast literature on clinical disease association, little direct mechanistic evidence is currently available demonstrating that either disease influences the progression of the other, but common pharmacological approaches could slow the progression of these diseases. Here, we review the clinical and scientific literature to discuss whether mechanisms beyond preexisting conditions, lifestyle, and weight gain contribute to the development of COPD associated with diabetes. Specifically, we outline environmental and genetic confounders linked with these diseases.

Interplay Between the Immune and Endocrine Systems in the Lung: Implications for TB Susceptibility

The role of the endocrine system on the immune response, especially in the lung, remains poorly understood. Hormones play a crucial role in the development, homeostasis, metabolism, and response to the environment of cells and tissues. Major infectious and metabolic diseases, such as tuberculosis and diabetes, continue to converge, necessitating the development of a clearer understanding of the immune and endocrine interactions that occur in the lung. Research in bacterial respiratory infections is at a critical point, where the limitations in identifying and developing antibiotics is becoming more profound. Hormone receptors on alveolar and immune cells may provide a plethora of targets for host-directed therapy. This review discusses the interactions between the immune and endocrine systems in the lung. We describe hormone receptors currently identified in the lungs, focusing on the effect hormones have on the pulmonary immune response. Altered endocrine responses in the lung affect the balance between pro- and anti-inflammatory immune responses and play a role in the response to infection in the lung. While some hormones, such as leptin, resistin and lipocalin-2 promote pro-inflammatory responses and immune cell infiltration, others including adiponectin and ghrelin reduce inflammation and promote anti-inflammatory cell responses. Furthermore, type 2 diabetes as a major endocrine disease presents with altered immune responses leading to susceptibility to lung infections, such as tuberculosis. A better understanding of these interactions will expand our knowledge of the mechanisms at play in susceptibility to infectious diseases and may reveal opportunities for the development of host-directed therapies.

Glycation-induced modification of tissue-specific ECM proteins: A pathophysiological mechanism in degenerative diseases

BACKGROUND

Glycation driven generation of advanced glycation end products (AGEs) and their patho-physiological role in human degenerative diseases has remained one of the thrust areas in the mainstream of disease biology. Glycation of extracellular matrix (ECM) proteins have deleterious effect on the mechanical and functional properties of tissues. Owing to the adverse pathophysiological concerns of glycation, there is a need to decipher the underlying mechanisms.

SCOPE OF REVIEW

AGE-modified ECM proteins affect the cell in the vicinity by altering protein structure-function, matrix-matrix or matrix-cell interaction and by activating signalling pathway through receptor for AGE. This review is intended for addressing the AGE-induced modification of tissue-specific ECM proteins and its implication in the pathogenesis of various organ-specific human ailments.

MAJOR CONCLUSIONS

The glycation affects the canonical cell behaviour due to alteration in the interaction of glycated ECM with receptors like integrins and discodin domain, and the signalling cues generated subsequently affect the downstream signalling pathways. Consequently, the variation of structural and functional properties of tissues due to matrix glycation helps in the initiation or progression of the disease condition.

GENERAL SIGNIFICANCE

This review offers comprehensive knowledge about the remodelling of glycation induced ECM and tissue-specific pathological concerns. As glycation of ECM affects the normal tissues and cell behaviour, the scientific discourse may also provide cues for developing candidate drugs that may help in attenuating the adverse effects of AGEs and perhaps open a research window of tailoring novel strategies for the management of glycation induced human degenerative diseases.

Cytokine and Adhesion Molecule Expression Induced by Different Strains of Staphylococcus aureus in Type 1 Diabetic Rats: Role of Insulin

Introduction: Staphylococcus aureus may provoke peritonitis and death, especially in immunocompromized individuals such as diabetic patients. We evaluated the role of insulin in S. aureus-induced peritoneal infection in diabetic and non-diabetic rats. Materials/Methods: Alloxan-diabetic male Wistar rats and their respective controls received intraperitoneal injections of different strains of S. aureus or sterile phosphate-buffered saline. After 3 days of infection, the first set of diabetic and non-diabetic rats received 4 and 1 IU, respectively, of neutral protamine Hagedorn insulin and were analyzed 8 h later. The second set of diabetic and non-diabetic rats received 4 and 1 IU, respectively, of insulin 2 h before intraperitoneal infection and a half dose of insulin at 5 p.m. for the next 2 days and were analyzed 16 h later. The following measurements were performed: (a) number of cells in the peritoneal lavage fluid (PeLF), white blood cell count, and blood glucose; (b) serum insulin and corticosterone; (c) cytokine levels in the PeLF; (d) expression of adhesion molecules in the vascular endothelium; and (e) microbicidal activity. Results: Diabetic rats showed an increased number of polymorphonuclear leukocytes (PMNs) and increased concentrations of CINC-1, IL-4, and IFN-γ in the PeLF after infection with the ATCC 25923 or N315 αHL⁺ strain. The mesenteric expression of PECAM-1 was increased after infection with the N315 HLA⁺ strain. ICAM-1 expression was increased with ATCC infection. Treatment of diabetic rats with a single dose of insulin restored CINC-1 levels in the PeLF for both strains; however, PMN migration, IL-4, and IFN-γ were restored in rats infected with the ATCC strain, whereas the PeLF concentrations of CINC-2, IL-1β, and IL-4 were increased in N315-infected animals. Insulin restored PMN migration and CINC-2 levels in the PeLF in ATCC-infected rats. After multiple treatments with insulin, the levels of IL-1β, IL-6, and IFN-γ were increased in the PeLF of diabetic rats after infection with either strain, and CINC-2 levels were restored in N315-infected animals. Conclusion: These results suggest that insulin distinctively modulates cytokine production or release, PMN leukocyte migration, and adhesion molecule expression during the course of peritonitis induced by different strains of S. aureus.

Insulin Modulates Paracoccidioides brasiliensis-Induced Inflammation by Restoring the Populations of NK Cells, Dendritic Cells, and B Lymphocytes in Lungs

Paracoccidioidomycosis, a key issue for Brazilian health service, can be aggravated in patients with impaired immunological responses, such as diabetic patients. We evaluated the role of insulin in inflammatory parameters in diabetic and nondiabetic mice using a systemic mycosis Paracoccidioides brasiliensis (Pb) model. Diabetic C57BL-6 mice and controls were infected with Pb18 and treated with insulin for 12 days prior to experiments. After 55 days, infected diabetic mice exhibited fewer leukocytes in both peritoneal lavage fluid (PeLF) and bronchoalveolar lavage fluid and reduced secretion of interleukin- (IL-) 6 in lungs. In addition, diabetic mice presented a reduced influx of TCD4+ cells, TCD8+ cells, B lymphocytes, NK cells, and dendritic cells compared to control infected groups. Insulin treatment restored the leukocyte number in PeLF and restored the presence of B lymphocytes, dendritic cells, and NK cells in lungs of diabetic animals. The data suggest that diabetic mice present impaired immunological response to Pb18 infection and insulin modulates inflammation by reducing IL-6 levels in lung and CINC-1 levels in spleen and liver homogenates, restoring leukocyte concentrations in PeLF and also restoring populations of dendritic cells and B lymphocytes in lungs of diabetic mice, permitting the host to better control the infection.

Insulin Modulates Cytokine Release, Collagen and Mucus Secretion in Lung Remodeling of Allergic Diabetic Mice

INTRODUCTION

The role of insulin in lung remodeling in a model of asthma in healthy and diabetic mice was evaluated.

MATERIAL AND METHODS

Diabetic male BALB/c mice (alloxan, 50 mg/kg, intravenous) and controls were sensitized by subcutaneous (s.c.) injection of ovalbumin (OA, 20 µg) in aluminum hydroxide (Al(OH)3, 2 mg) 10 days after the alloxan injection and received the same dose 12 days later. Six days after the last sensitization, animals were nebulized with OA solution for 7 days. The first set of diabetic and control mice received 2 and 1 IU, respectively, of s.c. neutral protamine Hagedorn (NPH) insulin and were analyzed 8 h later. The second set of diabetic and control mice received 2 and 1 IU, respectively, of insulin 12 h before the OA challenge and half doses of insulin 2 h before each the seven OA challenges. Twenty-four hours after the last challenge, the following analyses were performed: (a) quantification of the cells in the bronchoalveolar lavage fluid (BALF), the white cell count, and blood glucose; (b) morphological analysis of lung tissues by hematoxylin and eosin staining; (c) quantification of collagen deposition in lung tissues and mucus by morphometric analysis of histological sections stained with Masson's trichrome and periodic acid-Schiff (PAS), respectively; and (d) quantification of the cytokine concentrations (IL-4, IL-5, and IL-13) in the BALF supernatant.

RESULTS

Compared to controls, diabetic mice had significantly reduced inflammatory cells (81%) in the BALF, no eosinophils in the BALF and peripheral blood and reduced collagen deposition and mucus in the lungs. BALF concentrations of IL-4 (48%) and IL-5 (31%) decreased and IL-13 was absent. A single dose of insulin restored peripheral blood eosinophils and BALF mononuclear cells but not BALF eosinophils, collagen deposition, and mucus levels. However, multiple doses of insulin restored both total cells and eosinophils in the BALF and peripheral blood, BALF cytokines, and collagen deposition and mucus secretion into the lungs.

CONCLUSION

The results suggest that insulin modulates the production/release of cytokines, cell migration, deposition of collagen, and mucus secretion in lung remodeling of a mouse model of asthma.

Comparison between Variable and Conventional Volume-Controlled Ventilation on Cardiorespiratory Parameters in Experimental Emphysema

Emphysema is characterized by loss of lung tissue elasticity and destruction of structures supporting alveoli and capillaries. The impact of mechanical ventilation strategies on ventilator-induced lung injury (VILI) in emphysema is poorly defined. New ventilator strategies should be developed to minimize VILI in emphysema. The present study was divided into two protocols: (1) characterization of an elastase-induced emphysema model in rats and identification of the time point of greatest cardiorespiratory impairment, defined as a high specific lung elastance associated with large right ventricular end-diastolic area; and (2) comparison between variable (VV) and conventional volume-controlled ventilation (VCV) on lung mechanics and morphometry, biological markers, and cardiac function at that time point. In the first protocol, Wistar rats (n = 62) received saline (SAL) or porcine pancreatic elastase (ELA) intratracheally once weekly for 4 weeks, respectively. Evaluations were performed 1, 3, 5, or 8 weeks after the last intratracheal instillation of saline or elastase. After identifying the time point of greatest cardiorespiratory impairment, an additional 32 Wistar rats were randomized into the SAL and ELA groups and then ventilated with VV or VCV (n = 8/group) [tidal volume (V_T) = 6 mL/kg, positive end-expiratory pressure (PEEP) = 3 cmH₂O, fraction of inspired oxygen (FiO₂) = 0.4] for 2 h. VV was applied on a breath-to-breath basis as a sequence of randomly generated V_T values (mean V_T = 6 mL/kg), with a 30% coefficient of variation. Non-ventilated (NV) SAL and ELA animals were used for molecular biology analysis. The time point of greatest cardiorespiratory impairment, was observed 5 weeks after the last elastase instillation. At this time point, interleukin (IL)-6, cytokine-induced neutrophil chemoattractant (CINC)-1, amphiregulin, angiopoietin (Ang)-2, and vascular endothelial growth factor (VEGF) mRNA levels were higher in ELA compared to SAL. In ELA animals, VV reduced respiratory system elastance, alveolar collapse, and hyperinflation compared to VCV, without significant differences in gas exchange, but increased right ventricular diastolic area. Interleukin-6 mRNA expression was higher in VCV and VV than NV, while surfactant protein-D was increased in VV compared to NV. In conclusion, VV improved lung function and morphology and reduced VILI, but impaired right cardiac function in this model of elastase induced-emphysema.

Effects of the association of diabetes and pulmonary emphysema on cardiac structure and function in rats

Chronic obstructive pulmonary disease is often associated with chronic comorbid conditions of cardiovascular disease, diabetes mellitus and hypertension. This study aimed to investigate the effects of the association of diabetes and pulmonary emphysema on cardiac structure and function in rats. Wistar rats were divided into control non-diabetic instilled with saline (CS) or elastase (CE), diabetic instilled with saline (DS) or elastase (DE), DE treated with insulin (DEI) groups and echocardiographic measurements, morphometric analyses of the heart and lungs, and survival analysis conducted 50 days after instillation. Diabetes mellitus was induced [alloxan, 42 mg/kg, intravenously (iv)] 10 days before the induction of emphysema (elastase, 0.25 IU/100 g). Rats were treated with NPH insulin (4 IU before elastase plus 2 IU/day, 50 days). Both CE and DE exhibited similar increases in mean alveolar diameter, which are positively correlated with increases in right ventricular (RV) wall thickness (P = 0.0022), cavity area (P = 0.0001) and cardiomyocyte thickness (P = 0.0001). Diabetic saline group demonstrated a reduction in left ventricular (LV) wall, interventricular (IV) septum, cardiomyocyte thickness and an increase in cavity area, associated with a reduction in LV fractional shortening (P < 0.05), and an increase in LViv relaxation time (P < 0.05). Survival rate decreased from 80% in DS group to 40% in DE group. In conclusion, alloxan diabetes did not affect RV hypertrophy secondary to chronic emphysema, even in the presence of insulin. Diabetes per se induced left ventricular dysfunction, which was less evident in the presence of RV hypertrophy. Survival rate was substantially reduced as a consequence, at least in part, of the coexistence of RV hypertrophy and diabetic cardiomyopathy.