Ultrastructural immunogold localization of nitric oxide synthase isoforms in rat and human eosinophils
Abstract The involvement of nitric oxide (NO) as both pro
and anti-inflammatory agent in allergic, airway inflammatory,
and asthmatic diseases and the active participation of
eosinophils in such ailments have been previously suggested.
NO modulates eosinophil number, migration and
their survival. The microenvironment of NO synthase
(NOS) in subcellular organelles determines its rate and
efficiency of catalysis, which in turn influences NO
generation at distinct intracellular locales. The present
study was undertaken to assess the intracellular distribution
of NOS isoforms by transmission electron microscopy
followed by morphometric analysis in human and rat
eosinophils. Rat eosinophils were explored in parallel, and
since they are widely used as model systems to mimic
human diseases, a comparative study on NOS localization
patterns might provide useful information in deciphering
NO role in diverse aspects of eosinophil-related inflammatory
ailments. The results demonstrated predominance of
neuronal NOS (nNOS) in the eosinophilic granules and
even distribution of inducible NOS (iNOS) and nNOS in
the cytoplasm and nucleus of human eosinophils. In rat
eosinophils, however, iNOS was mainly localized in the eosinophilic granules and nucleus, while nNOS was
distributed evenly in cytoplasm and nucleus. Distribution
of endothelial NOS (eNOS) in eosinophils was scanty.
Differences in NOS isoforms and their localization in
human and rat cells might have implications in differential
mode of catalysis and functional contribution to eosinophil
physiology and pathology, warranting detailed investigations.
The present study highlights species-specific differences
in the relative abundance and distribution pattern of
NOS isoforms in rat and human eosinophils, which should
be considered cautiously in interpreting the rat data to
humans.
and anti-inflammatory agent in allergic, airway inflammatory,
and asthmatic diseases and the active participation of
eosinophils in such ailments have been previously suggested.
NO modulates eosinophil number, migration and
their survival. The microenvironment of NO synthase
(NOS) in subcellular organelles determines its rate and
efficiency of catalysis, which in turn influences NO
generation at distinct intracellular locales. The present
study was undertaken to assess the intracellular distribution
of NOS isoforms by transmission electron microscopy
followed by morphometric analysis in human and rat
eosinophils. Rat eosinophils were explored in parallel, and
since they are widely used as model systems to mimic
human diseases, a comparative study on NOS localization
patterns might provide useful information in deciphering
NO role in diverse aspects of eosinophil-related inflammatory
ailments. The results demonstrated predominance of
neuronal NOS (nNOS) in the eosinophilic granules and
even distribution of inducible NOS (iNOS) and nNOS in
the cytoplasm and nucleus of human eosinophils. In rat
eosinophils, however, iNOS was mainly localized in the eosinophilic granules and nucleus, while nNOS was
distributed evenly in cytoplasm and nucleus. Distribution
of endothelial NOS (eNOS) in eosinophils was scanty.
Differences in NOS isoforms and their localization in
human and rat cells might have implications in differential
mode of catalysis and functional contribution to eosinophil
physiology and pathology, warranting detailed investigations.
The present study highlights species-specific differences
in the relative abundance and distribution pattern of
NOS isoforms in rat and human eosinophils, which should
be considered cautiously in interpreting the rat data to
humans.