Chronic and intermittent hypoxia differentially regulate left ventricular inflammatory and extracellular matrix...

Area of Science:

• Cardiovascular Physiology
• Molecular Biology
• Hypoxia Research

Background:

• Hypoxia, a condition of low oxygen, significantly impacts cardiovascular health.
• Different patterns of hypoxia, such as chronic sustained hypoxia (CSH) and chronic intermittent hypoxia (CIH), may elicit distinct physiological responses.
• Understanding these differential responses is crucial for developing targeted therapeutic strategies.

Purpose of the Study:

• To investigate and compare the specific molecular and structural changes in the left ventricle (LV) of male Sprague Dawley rats under CSH and CIH.
• To elucidate the differential inflammatory and extracellular matrix gene expression profiles induced by CSH versus CIH.
• To validate gene expression changes with corresponding protein level alterations.

Main Methods:

• Male Sprague Dawley rats were exposed to normoxia (control), CSH, or CIH for 7 days.
• Gene expression analysis was performed on 168 inflammatory, extracellular matrix, and adhesion molecule genes.
• Right ventricle/body weight and lung/body weight ratios were measured.
• Myocyte cross-sectional area and perivascular fibrosis were assessed.
• Key protein levels (MMP-9, fibronectin, HIF-2α, eNOS) were quantified.

Main Results:

• CSH significantly increased inflammatory gene expression (e.g., Ltb, Col5a1, MMP-11) and right ventricle/body weight ratio.
• CIH led to decreased inflammatory gene expression (e.g., Ltb, Spp1) and reduced inflammatory markers (HIF-2α, eNOS).
• CIH also resulted in increased Laminin β2 gene expression, decreased MMP-9 and fibronectin (gene and protein), increased myocyte size, and perivascular fibrosis.

Conclusions:

• The study demonstrates that 7 days of hypoxia induce differential inflammatory responses in the LV.
• CSH promotes an increase in cardiac inflammation, whereas CIH appears to reduce it.
• This is the first report detailing specific and distinct molecular and structural alterations in the LV under CSH and CIH conditions.