464
K. malek et al.
and composition of lipids in the tissue. the toF-SImS analysis in turn identified
precisely some of the lipids present in the liver. Cholesterol, monoacylglycerols
and diacylglycerols (dAg) were detected as highly abundant species. Whilst saturated dAg species were detected mostly outside of steatotic vesicles, a high content of cholesterol along with dAg containing at least one unsaturated acyl chain
is selectively concentrated in the vesicles, confirming the FtIR results. despite
the fact that the h&E histological examination of the normal and steatotic liver
showed similar morphological features of non-steatotic regions in both samples, the
FtIR spectra revealed important biochemical changes. Non-steatotic hepatocytes
of the fatty liver are characterized by the higher intensity of the stretching modes
of lipid and carbohydrate moieties. the toF-SImS imaging of the same region of
the samples demonstrated the presence of small lipid droplets (< 10 μm) containing
dAgs. these droplets are likely to correspond to the first event of lipid accretion.
thus, the combination of the two imaging techniques demonstrates early metabolic
disturbance in fatty acids of the liver. In conclusion, infrared microspectroscopy
hinted at global chemical changes that could be further investigated by the selective
and sensitive mass spectrometry [155].
A detailed study combining FtIR imaging, histological analysis and sera markers of the liver function, on mouse liver injury induced by a popular pain-relief
APAP has been undertaken by gautam et al. [156]. the FtIR spectral changes were
detected in the liver tissue after 0.5 h of oral drug administration. they revealed
a significant lowering of the glycogen content accompanied by an increase in the
concentration of cholesteryl esters and in the dNA/RNA ratio. this was highlighted
by the intensity variation of bands at 1171 and 966/996 cm
−1
, respectively. the
changes of glycogen and cholesteryl esters were sustained up to 6 h post APAP
treatment, while the dNA/RNA ratio increased significantly after 0.5 h, peaking at
1.5 h, thereafter was sustained up to 6 h. these changes correlated with a drop in
total gSh and an increase in malonaldehyde, but the increase in ALt amounts and
histological evidence of the liver injury occurred only after 3 h period and peaked
with maximum liver damage by 6 h. Interestingly, the spectral changes found in
the tissue were similar to spectral features of sera, indicating a possible application
of FtIR spectroscopy in monitoring of hepatoxicity. Additionally, FtIR data from
imaging of the tissue showed molecular changes due to pre- and post-treatment of
the APAP treated mice with an antidote—L-methionine. ALt amounts indicated
inhibiting the hepatotoxic effect, but FtIR spectra confirmed that only in case of
L-methionine pre-treatment. the glycogen and dNA levels were restored to the
level observed in the control group, while the content of cholesteryl esters remained
elevated. this implicates that glycogen and dNA amounts might be indicative for
the early rise of oxidative stress [156].
K. malek et al.
and composition of lipids in the tissue. the toF-SImS analysis in turn identified
precisely some of the lipids present in the liver. Cholesterol, monoacylglycerols
and diacylglycerols (dAg) were detected as highly abundant species. Whilst saturated dAg species were detected mostly outside of steatotic vesicles, a high content of cholesterol along with dAg containing at least one unsaturated acyl chain
is selectively concentrated in the vesicles, confirming the FtIR results. despite
the fact that the h&E histological examination of the normal and steatotic liver
showed similar morphological features of non-steatotic regions in both samples, the
FtIR spectra revealed important biochemical changes. Non-steatotic hepatocytes
of the fatty liver are characterized by the higher intensity of the stretching modes
of lipid and carbohydrate moieties. the toF-SImS imaging of the same region of
the samples demonstrated the presence of small lipid droplets (< 10 μm) containing
dAgs. these droplets are likely to correspond to the first event of lipid accretion.
thus, the combination of the two imaging techniques demonstrates early metabolic
disturbance in fatty acids of the liver. In conclusion, infrared microspectroscopy
hinted at global chemical changes that could be further investigated by the selective
and sensitive mass spectrometry [155].
A detailed study combining FtIR imaging, histological analysis and sera markers of the liver function, on mouse liver injury induced by a popular pain-relief
APAP has been undertaken by gautam et al. [156]. the FtIR spectral changes were
detected in the liver tissue after 0.5 h of oral drug administration. they revealed
a significant lowering of the glycogen content accompanied by an increase in the
concentration of cholesteryl esters and in the dNA/RNA ratio. this was highlighted
by the intensity variation of bands at 1171 and 966/996 cm
−1
, respectively. the
changes of glycogen and cholesteryl esters were sustained up to 6 h post APAP
treatment, while the dNA/RNA ratio increased significantly after 0.5 h, peaking at
1.5 h, thereafter was sustained up to 6 h. these changes correlated with a drop in
total gSh and an increase in malonaldehyde, but the increase in ALt amounts and
histological evidence of the liver injury occurred only after 3 h period and peaked
with maximum liver damage by 6 h. Interestingly, the spectral changes found in
the tissue were similar to spectral features of sera, indicating a possible application
of FtIR spectroscopy in monitoring of hepatoxicity. Additionally, FtIR data from
imaging of the tissue showed molecular changes due to pre- and post-treatment of
the APAP treated mice with an antidote—L-methionine. ALt amounts indicated
inhibiting the hepatotoxic effect, but FtIR spectra confirmed that only in case of
L-methionine pre-treatment. the glycogen and dNA levels were restored to the
level observed in the control group, while the content of cholesteryl esters remained
elevated. this implicates that glycogen and dNA amounts might be indicative for
the early rise of oxidative stress [156].