Hibernating myocardium results in partial sympathetic denervation and nerve sprouting

Am J Physiol Heart Circ Physiol. 2013 Jan 15;304(2):H318-27. doi: 10.1152/ajpheart.00810.2011. Epub 2012 Nov 2.

Abstract

Hibernating myocardium due to chronic repetitive ischemia is associated with regional sympathetic nerve dysfunction and spontaneous arrhythmic death in the absence of infarction. Although inhomogeneity in regional sympathetic innervation is an acknowledged substrate for sudden death, the mechanism(s) responsible for these abnormalities in viable, dysfunctional myocardium (i.e., neural stunning vs. sympathetic denervation) and their association with nerve sprouting are unknown. Accordingly, markers of sympathetic nerve function and nerve sprouting were assessed in subendocardial tissue collected from chronically instrumented pigs with hibernating myocardium (n = 18) as well as sham-instrumented controls (n = 7). Hibernating myocardium exhibited evidence of partial sympathetic denervation compared with the normally perfused region and sham controls, with corresponding regional reductions in tyrosine hydroxylase protein (-32%, P < 0.001), norepinephrine uptake transport protein (-25%, P = 0.01), and tissue norepinephrine content (-45%, P < 0.001). Partial denervation induced nerve sprouting with regional increases in nerve growth factor precursor protein (31%, P = 0.01) and growth associated protein-43 (38%, P < 0.05). All of the changes in sympathetic nerve markers were similar in animals that developed sudden death (n = 9) compared with electively terminated pigs with hibernating myocardium (n = 9). In conclusion, sympathetic nerve dysfunction in hibernating myocardium is most consistent with partial sympathetic denervation and is associated with regional nerve sprouting. The extent of sympathetic remodeling is similar in animals that develop sudden death compared with survivors; this suggests that sympathetic remodeling in hibernating myocardium is not an independent trigger for sudden death. Nevertheless, sympathetic remodeling likely contributes to electrical instability in combination with other factors.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Arrhythmias, Cardiac / etiology
  • Arrhythmias, Cardiac / physiopathology
  • Biomarkers / metabolism
  • Death, Sudden, Cardiac / etiology
  • Disease Models, Animal
  • GAP-43 Protein / metabolism
  • Heart / innervation*
  • Myocardial Stunning / complications
  • Myocardial Stunning / metabolism
  • Myocardial Stunning / pathology
  • Myocardial Stunning / physiopathology*
  • Myocardium / metabolism
  • Myocardium / pathology
  • Nerve Growth Factor / metabolism
  • Neurogenesis*
  • Norepinephrine / metabolism
  • Norepinephrine Plasma Membrane Transport Proteins / metabolism
  • Protein Precursors / metabolism
  • Swine
  • Sympathetic Nervous System / metabolism
  • Sympathetic Nervous System / pathology
  • Sympathetic Nervous System / physiopathology*
  • Tyrosine 3-Monooxygenase / metabolism

Substances

  • Biomarkers
  • GAP-43 Protein
  • Norepinephrine Plasma Membrane Transport Proteins
  • Protein Precursors
  • Nerve Growth Factor
  • Tyrosine 3-Monooxygenase
  • Norepinephrine