Effect of aging on norepinephrine-related proliferative response in primary cultured periportal and perivenous hepatocytes

Influence of constant lightning on liver health: an experimental study

Light pollution has become a serious problem in many urbanized areas of the world. The impact of prolonged exposure to light and consequent disruption of natural circadian rhythms has significant health implications. The current study was undertaken to evaluate the effect of prolonged exposure to light, simulating urban light pollution, on liver health. In order to evaluate the effect of prolonged exposure to light, we examined the morphofunctional state, immunohistochemical and micromorphometric parameters of rat liver in normal conditions and following prolonged lighting exposure. Our results show that nocturnal light disruption triggers a cell death in the liver within 3 weeks (necrosis and apoptosis of hepatocytes) and stimulates a change in normal cellular karyometric parameters. At the same time, intracellular regeneration takes place within the organ, which manifests through hepatocyte hypertrophy. Under the influence of constant illumination, the circadian rhythms (CRs) of the size of hepatocytes and their nuclei are restructured, and the rhythm of the nuclear-cytoplasmic ratio is destroyed. The destruction of the CR of expression of p53 and Ki-67 also occurs against the background of the rearrangement of the daily rhythmicity of Per2 and Bmal1. The revealed changes in the morphofunctional state of the liver under the influence of light pollution indicate that a violation of normal illumination regimes is a potent factor leading to significant structural changes in the liver.

Morphofunctional State and Circadian Rhythms of the Liver of Female Rats under the Influence of Chronic Alcohol Intoxication and Constant Lighting

A separate and combined effect of constant illumination and chronic alcohol intoxication (CAI) on diurnal dynamics of micromorphometric parameters of hepatocytes in female Wistar rats and p53, Ki-67, PER2, BMAL1, and ADH5 expression in these cells were studied. The increase in apoptotic activity and proliferation in all animals under the action of chronodestructors is shown. All experimental animals showed a decrease in BMAL1 expression and increase in PER2 expression; ADH5 is overexpressed under the influence of ethanol. Circadian rhythms (CRs) of BMAL1, PER2, p53, and Ki-67 expression persist in all groups, except combined action of chronodestructors, and ADH5 CRs persist in all groups—thus, these rhythms in females are quite stable. CRs of the hepatocyte nuclei area are preserved in all the studied groups, although they undergo a significant shift. At the same time, the CRs of the hepatocyte area are destroyed under the action of light, both independently and in combination with CAI, and the CR of the nuclear-cytoplasmic ratio (NCR) is destroyed by exposure to CAI. It can be assumed that CRs of the hepatocyte area are significantly affected by dark deprivation and NCR rhythm is sensitive to ethanol consumption, while the stability of studied genes’ expression rhythms at separate influences of studied chronodestructors is maintained by yet unknown adaptation mechanisms. It is necessary to note that, according to our previous studies of male rats, rat females show significantly greater stability of the studied CRs.

Morphofunctional State and Circadian Rhythms of the Liver under the Influence of Chronic Alcohol Intoxication and Constant Lighting

A study of the influence of chronic alcohol intoxication, constant illumination and their combined effects on the morphofunctional state of the rat liver and the circadian rhythms (CR) of the studied parameters of the organism was carried out. It was found that both alcohol and constant illumination caused significant changes in the structure of the liver, as well as in the circadian rhythmicity of micromorphometric parameters of hepatocytes, ALT, and total and direct bilirubin rhythms; however, the combined effects of ethanol and constant illumination had the most significant effect on the studied parameters of the organism. These two factors caused disturbances in the circadian rhythms of the micromorphometric parameters of hepatocytes, disruption of the circadian rhythms of total protein, albumin, AST, ALT, and direct and total bilirubin, as well as disturbances in the expression and rhythmicity of the studied clock genes against a background of the development of an inflammatory process in the liver.

Sympathetic neurotransmitters promote the process of recellularization in decellularized liver matrix via activating the IL-6/Stat3 pathway

Recellularized liver, as an approach for hepatic tissue engineering, is an effective alternative to orthotopic liver transplantation for end-stage hepatic failure. When compared with normal liver, recellularized liver has a disparity in hepatocyte viability and function, owing to the difficulty of fully simulating the microenvironment of liver. Although the sympathetic nervous system (SNS) is considered an important constituent of liver function, few studies have examined the effect of the SNS on hepatic tissue engineering. It is imperative to explore the regulation of the SNS on a tissue-like configuration to obtain an intact recellularized liver with better hepatic function. We have observed that various subtypes of adrenergic receptors (ARs) are expressed on the hepatocyte membrane. Salbutamol, an agonist of β2-AR, promoted cell proliferation, albumin secretion and urea synthesis in the recellularized liver. Cytokines were screened in isoprenaline/salbutamol-treated recellularized liver, and the expression of IL-6 was significantly increased. Isoprenaline or salbutamol especially promoted the expression of Stat 3 and phosphorylated Stat 3, contributing to the activation of IL-6/Stat 3 signalling in promoting hepatocyte proliferation and recellularized liver function. This study suggests that activation of β2-AR accelerated hepatocyte proliferation and improved recellularized liver function by mediating the IL-6/Stat 3 signalling pathway, indicating that nervous system regulation may be an essential component contributing to the complexity of recellularized liver in tissue engineering.

Insulin resistance in the liver: deficiency or excess of insulin?

In insulin-resistant states (obesity, pre-diabetes, and type 2 diabetes), hepatic production of glucose and lipid synthesis are heightened in concert, implying that insulin deficiency and insulin excess coexists in this setting. The fact that insulin may be inadequate or excessive at any one point in differing organs and tissues has many biologic ramifications. In this context the concept of metabolic compartmentalization in the liver is offered herein as one perspective of this paradox. In particular, we focus on the hypothesis that insulin resistance accentuates differences in periportal and perivenous hepatocytes, namely periportal glucose production and perivenous lipid synthesis. Subsequently, excessive production of glucose and accumulation of lipids could be expected in the livers of patients with obesity and insulin resistance. Overall, in this review, we provide our integrative perspective regarding how excessive production of glucose in periportal hepatocytes and accumulation of lipids in perivenous hepatocytes interact in insulin resistant states.