Derangement of Kupffer cell functioning and hepatotoxicity in hyperthyroid rats subjected to acute iron overload

Kupffer cell stimulation in the isolated perfused rat liver triggers nuclear factor-κB DNA binding activity

Activation of transcription factor NF-kappaB (electrophoretic mobility shift assay) was investigated in the isolated perfused rat liver infused with 0.5 mg of colloidal carbon/ml for 5-20 min, in relation to carbon phagocytosis and carbon-induced O(2) consumption. Experiments were carried out in control rats and in animals treated with the Kupffer cell inactivator gadolinium chloride (GdCl(3)). Carbon uptake and carbon-induced O(2) consumption by perfused livers exhibited a linear increase as a function of the perfusion time, leading to constant O(2)/carbon uptake ratios, with low (0.04-0.15%) fractional sinusoidal lactate dehydrogenase release in the 5-20 min perfusion time studied. NF-kappaB DNA binding activity showed a maximal enhancement at 10 min of carbon perfusion, a response that was sustained at a lower extent at 15 and 20 min of carbon stimulation. After 10 min of carbon infusion, NF-kappaB activation, carbon-induced O(2) consumption, and carbon uptake were diminished by 84%, 94%, and 64% by GdCl(3) treatment (P < 0.05), respectively. It is concluded that the respiratory burst of carbon-stimulated Kupffer cells triggers NF-kappaB activation in the isolated perfused liver, a response that is elicited under optimal conditions of Kupffer cell function and organ viability.

Biliary proteins and their redox status changes in gallstone patients

BACKGROUND

Proteins might act as pronucleating agents of cholesterol crystallization in bile. However, little is known about the redox status of biliary proteins in humans and their interaction with crystallization of biliary cholesterol.

MATERIALS AND METHODS

Gallbladder biles were obtained at cholecystectomy from 86 symptomatic patients with either cholesterol gallstones (32 multiple and 32 solitary stones) or pigment stones (n = 22), and studied for protein redox status [carbonyl and sulfhydryl (PSH) concentrations], total lipid and protein levels and cholesterol saturation index (CSI). First appearance of cholesterol crystals in ultrafiltered bile (crystal observation time, COT) was studied with polarizing light microscopy during 21 days.

RESULTS

Patients with cholesterol stones had significantly shorter COT (3 days vs. >21 days, P < 0.05), higher CSI (149 +/- 10% vs. 97 +/- 7%, P < 0.05) and higher total biliary proteins (1.96 +/- 0.1 mg mL(-1) vs. 0.55 +/- 0.1 mg mL(-1), P < 0.05) than patients with pigment stones. Patients with cholesterol stones had significantly lower (P < 0.05) level of protein sulfhydryl concentrations (18 +/- 4 nmol mg(-1) protein vs. 49 +/- 16 nmol mg(-1) protein), while total lipid and carbonyl proteins concentrations were similar between cholesterol and pigment stone patients. Crystallization probability was influenced by the number/type of gallstones (multiple > solitary > pigment stones, P = 0.009) and total protein concentration (high > low levels, P = 0.004). COT was negatively correlated with total protein content (r = -0.45, P = 0.03).

CONCLUSIONS

Biles with cholesterol stones show high CSI and total protein concentration, and rapid COT, which is even faster in patients with multiple stones and high protein concentration. Low PSH levels in cholesterol stone patients point to a biochemical shift, potentially able to affect cholesterol crystallization.

Thyroid hormone preconditioning: protection against ischemia-reperfusion liver injury in the rat

Recently, we reported that oxidative stress due to 3,3',5-triiodothyronine (T(3))-induced calorigenesis up-regulates the hepatic expression of mediators promoting cell protection. In this study, T(3) administration in rats (single dose of 0.1 mg/kg intraperitoneally) induced significant depletion of reduced liver glutathione (GSH), with higher protein oxidation, O(2) consumption, and Kupffer cell function (carbon phagocytosis and carbon-induced O(2) uptake). These changes occurred within a period of 36 hours of T(3) treatment in animals showing normal liver histology and lack of alteration in serum AST and ALT levels. Partial hepatic ischemia-reperfusion (IR) (1 h of ischemia via vascular clamping and 20 h reperfusion) led to 11-fold and 42-fold increases in serum AST and ALT levels, respectively, and significant changes in liver histology, with a 36% decrease in liver GSH content and a 133% increase in that of protein carbonyls. T(3) administration in a time window of 48 hours was substantially protective against hepatic IR injury, with a net 60% and 90% reduction in liver GSH depletion and protein oxidation induced by IR, respectively. Liver IR led to decreased DNA binding of nuclear factor-kappaB (NF-kappaB) (54%) and signal transducer and activator of transcription 3 (STAT3) (53%) (electromobility shift assay), with 50% diminution in the protein expression of haptoglobin (Western blot), changes that were normalized by T(3) preconditioning.

CONCLUSION

T(3) administration involving transient oxidative stress in the liver exerts significant protection against IR injury, a novel preconditioning maneuver that is associated with NF-kappaB and STAT3 activation and acute-phase response.

Iron, oxidative stress and human health

The amount of iron within the cell is carefully regulated in order to provide an adequate level of the micronutrient while preventing its accumulation to toxic levels. Iron excess is believed to generate oxidative stress, understood as an increase in the steady state concentration of oxygen radical intermediates. The main aspects of cellular metabolism of iron, with special emphasis on the role of iron with respect to oxidative damage to lipid membranes, are briefly reviewed here. Both in vitro and in vivo models are examined. Finally, a discussion of iron overload and its impact on human health is included. Overall, further studies are required to assess more effective means to limit iron-dependent damage, by minimizing the formation and release of free radicals in tissues when the cellular iron steady state concentration is increased either as a consequence of disease or by therapeutic iron supplementation.

Swelling of hepatocytes injured by oxidative stress suggests pathological changes related to macromolecular crowding

A fundamental property of living matter is the ability to establish and maintain order. Mild changes in cell volume have a role in metabolic control. Furthermore, cellular swelling is a way of living cells to react to a variety of stressors. Data from experimental pathology, biochemistry and biophysics and theoretical arguments from biology, biochemical evolution, cytology and biophysics are considered to attempt an integration of several current concepts on different subjects (intracellular compartmentation, cellular swelling, macromolecular crowding, perturbing and non-perturbing solutes). The purpose is to provide a framework for conceptualizing in modern terms the question whether cellular swelling induced by oxidative stress should be considered merely a cell adaptation balanced by antioxidant defenses and by other biochemical devices apt to preserve the intracellular environment and normal cell functioning, or whether swelling of high amplitude should be regarded as a true pathological change. The basic question dated 1982: "how crowded is the cytoplasm?" is a matter for discussion as far as swollen cells are concerned. This paper examines the liver for cellular swelling of high amplitude (about+30%) caused by iron or by thyroid hormone+iron (histological picture of "cloudy swelling") or the steatogenic poison CCl(4), also known as a source of oxyradicals, which causes an even more pronounced cellular swelling. In CCl(4)-toxic fatty liver the strong increase of tissue water is substantially masked by the parallel increase of tissue dry solids due to fat accumulation. This example of a "tissue dilution artefact" is discussed in connection with the increase of tissue water also in toxic fatty liver induced by white phosphorus and ethanol. In CCl(4)-toxic fatty liver the normal K(+)/Na(+) ratio (about 3) is substantially maintained, whereas the concentrations of the two cations ("perturbing osmolytes") in tissue water are noticeably decreased, a finding which was not further studied at the time the observations were made because biochemistry was not yet advanced enough to allow an explanation. Today, a logic hypothesis is that an increase of non-perturbing solutes such as taurine and betaine, maintains the physiological intracellular osmotic pressure and that the harmful effects of CCl(4) are limited because of the protective effects of these molecules and of molecular chaperones against damage by oxyradicals. However, as a consequence of cellular swelling, intracellular changes in ionic strength and macromolecular crowding should occur thus affecting enzyme activities. Models and techniques apt to investigate this problem experimentally are suggested.

Iron-induced changes in nitric oxide and superoxide radical generation in rat liver after lindane or thyroid hormone treatment

The involvement of cytosolic nitric oxide (NO) and mitochondrial superoxide radical (O2(.-)) production was evaluated as a mechanism triggering liver oxidative stress in lindane (40 mg/kg) or L-3,3',5-triiodothyronine (T3, 0.1 mg/kg for 2 consecutive days) treated animals (male Sprague-Dawley rats) subjected to iron overload (200 mg/kg). Lindane and iron led to 504 and 210% increases in the content of hepatic protein carbonyls as an index of oxidative stress, with a 706% enhancement being produced by their combined administration. T3 did not alter this parameter, whereas iron overload increased the content of protein carbonyls by 116% in hyperthyroid rats. Lindane increased NO generation by 106% without changes in generation of O2(.-), whereas iron enhanced both parameters by 109 and 80% over control values, respectively, with a net 33 and 46% decrease, respectively, being elicited by the combined treatment related to iron overload alone. Hyperthyroidism increased liver NO (69%) and O2(.-) (110%) generation compared to controls, effects that were either synergistically augmented or suppressed by iron overload, respectively. The in vitro addition of iron (1 micromol/mg protein) to liver cytosolic fractions from euthyroid (97%) and hyperthyroid (173%) rats also enhanced NO generation. The effects of iron overload on mitochondrial O2(.-) production by hyperthyroid rats were reproduced by the in vitro addition of 1 micromol iron/mg protein and abolished by the in vivo pretreatment with the iron chelator desferrioxamine (500 mg/kg). It is concluded that liver oxidative stress induced by iron overload is independent of NO and O2(.-) production in lindane-treated rats, whereas in hyperthyroid animals NO generation is a major factor contributing to this redox imbalance.

Effects of iron overload and lindane intoxication in relation to oxidative stress, Kupffer cell function, and liver injury in the rat

Parameters related to liver oxidative stress, Kupffer cell function, and hepatocellular injury were assessed in control rats and in animals subjected to lindane (40 mg/kg; 24 h) and/or iron (200 mg/kg; 4 h) administration. Independently of lindane treatment, iron overload enhanced the levels of iron in serum and liver. Biliary efflux of glutathione disulfide increased by 140, 160, or 335% by lindane, iron, or their combined administration, respectively, and the hepatic content of protein carbonyls was elevated by 5.84-, 2.95-, and 10-fold. Colloidal carbon uptake by perfused livers was not modified by lindane and/or iron, whereas gadolinium chloride (GdCl(3)) pretreatment diminished uptake by 60-72%. Carbon-induced liver O(2) uptake was not altered by lindane, whereas iron produced a 61% increase and the combined treatment led to a 72% decrease over control values. Pretreatment with GdCl(3) abolished these effects in all groups. Lindane-treated rats showed acidophilic hepatocytes in periportal areas and some hepatic cells with nuclear pyknosis, whereas iron overload led to moderate hyperplasia and hypertrophy of Kupffer cells and moderate inflammatory cell infiltration. Combined lindane-iron treatment led to hepatocytes with pyknotic nuclei, significant acidophilia, and extensive lymphatic and neutrophil infiltration in the portal space. Hepatic myeloperoxidase activity increased by 1.1-, 2.1-, or 6.7-fold by lindane, iron, or their combined administration, respectively. Liver sinusoidal lactate dehydrogenase efflux increased by 2.2-fold (basal conditions) and 9.7-fold (carbon infusion) in the lindane-iron treated rats, effects that were diminished by 35 and 78% by GdCl(3) pretreatment, respectively. These data support the contention that lindane sensitizes the liver to the damaging effects of iron overload by providing an added enhancement to the oxidative stress status in the tissue, and this may contribute to the alteration of the respiratory activity of Kupffer cells and the development of an inflammatory response.