Claudia dos Santos

Research Synopsis

1. My laboratory focuses on developing integrated systems biology and functional genomics approaches to: understanding molecular mechanisms of acute multiple organ failure (HEART and LUNG) in the critically ill (sepsis and acute respiratory distress syndrome ARDS)
2. developing an “informed” approach to the discovery of novel molecular targets for therapy including stem cell and gene therapy.

My lab is dedicated to applying novel whole throughput and computational strategies to identify - using a “candidate” gene approach - putative genes/molecules, pathways and networks involved in the pathophysiology, diagnosis, prognosis and management of critical illness: specifically I am interested in mechanisms of HEART and LUNG failure in critically ill patients.

Acute and Ventilator Induced Lung Injury –Bioinformatics was used to determine cyclic stretch is associated with a specific gene expression profile that underlies cellular remodeling in the setting of injury (dos Santos et al. CCM 2008). (ii) Response to injury is a complex, multigenic event that involves multiple factors acting at different times. I have shown that in part, the coordinated response of lung cells to cyclic injury is regulated by the stretch sensitive transcription factor activating transcription factor 3 (ATF3). To establish the biological importance of this finding, I used an ATF3 knock out mouse to demonstrate that ATF3 is a negative transcriptional regulator that acts to “counter-balance” the hyperinflammatory response (Akram et al. AJRCCM 2010 Appendix 2).

Combining microarray data using gene-gene meta-analysis has yielded a profile that has the potential to differentiate clinically relevant ALI (P. Hu et al. Plos One, 2011). We have recently developed ATF3 chimera to demonstrate the relative contribution of ATF3 expression in different cells to ALI/VILI (Shan et al. under revision, Appendix 4)

Mesenchymal Stem Cells (MSCs) in Multiorgan Injury: (iii) More recently my focus has shifted towards stem cells, which have an immunomodulatory and reparative potential. In collaboration we have shown that MSCs significantly decreased mortality in septic mice. Analysis of expression profiles from treated and untreated mice demonstrated an overall downregulation of inflammation-related genes, and a shift towards upregulation of genes involved in bacterial killing. These findings strongly suggest that the beneficial effects of MSCs extend beyond suppression of inflammation (Mei et al. AJRCCM 2010).

Global expression analysis points to a fundamental role of mitochondria related genes in conferring the beneficial effects of MSCs (dos Santos et al. Am J of Pathol, 2011 Appendix 1). Work from my lab has also shown that we can generate MSCs and that these can be used to attenuate fibroproliferative changes in the lung that occur secondary to dysregulated repair of lung injury (Maron_gutierrez et al. in press, Appendix 5)

Sepsis-induced Myocardial Depression: Myocardial Depression – (iv) I compared the transcriptional profile of wild type mice sensitive to sepsis induced myocardial depression with nitric oxide synthase deficient mice that are resistant. Sepsis-induced myocardial depression results in down regulation of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1a), involved in mitochondrial biogenesis and substrate bioenergy utilization.

Decrease in PGC1a was not present in iNOS deficient animals (dos Santos et al. CCM 2010). (iv) Treatment of wild type septic mice with Resveratrol – an antioxidant that increases PGC1a – protected septic animals from myocardial depression, suggesting that mitochondrial “resuscitation”, via preservation of PGC1a represents a potential treatment strategy for myocardial depression (dos Santos C et al. CCM 2012 Appendix 3)

Anti-cholinergic Anti-inflammatory Reflex in Critical Illness – (v) We have shown that stimulation of the anti-inflammatory cholinergic pathway mitigates mechanical injury caused by repetitive cyclic stretch associated with ventilator-induced lung injury.

In vivo (animal) and in vitro (human cellular) models, cyclic stretch injury is exacerbated by inhibition of the alpha 7 nicotinic receptor for acetylcholine, and that stimulation of this receptor results in down regulation of critical intracellular mediators of cyclic stretch injury. Moreover, in vivo electrical or pharmacological stimulation of the efferent vagus nerve protects animals from severe lung injury by reducing both inflammation and cellular apoptosis (dos Santos et al. AJRCCM 2010). This work opens up an entirely new line of therapeutic options in the field of acute lung injury.