Regulation of signal transduction and role of platelets in liver regeneration

Reenvisioning Traditional to Regenerative Therapeutic Advances in Managing Nonalcoholic Fatty Liver Disease in Diabetes Mellitus

Reports indicate the increasing prevalence of liver disorders in diabetes mellitus (DM) patients. Clinically, it has also been revealed that the existence of nonalcoholic fatty liver disease (NAFLD) enhances the incidence of type 2 diabetes mellitus (T2DM), while T2DM exacerbates NAFLD to extremely severe forms of steatohepatitis, cirrhosis, and hepatocellular carcinoma. This implies the coexistence and bidirectional nature of NAFLD and T2DM, which function synergistically to drive adverse consequences in clinical practice. For treatment of such comorbid state, though the existing practices such as lifestyle management, traditional Chinese medicines (TCM), and pharmaceuticals have offered somewhat relief, the debate continues about the optimal therapeutic impacts. Recent developments in the field of tissue engineering have led to a renewed interest in novel biomaterial alternatives such as stem cells. This might be attributable to their differentiation potential towards hepatic and pancreatic lineage. These cellular therapies could be further complemented by platelet-derived biomaterials, TCM formulations, or any specific drug. Based on these abovementioned approaches, we aimed to comprehensively analyze various preclinical and clinical studies from traditional to regenerative therapeutic approaches in managing concomitant NAFLD and T2DM.

Regulation of liver regeneration by prostaglandin E2 and thromboxane A2 following partial hepatectomy in rats

The implication of prostaglandin E₂ (PGE₂) and thromboxane A₂ (TXA₂) in the striking process of liver regeneration has been previously reported. However, their exact roles and downstream signals have not been utterly revealed. Therefore, the present study was conducted to explore whether inhibition of cyclooxygenase-2 (COX-2)-derived PGE₂ by celecoxib and blocking of TXA₂ action by seratrodast could alter the progression of liver regeneration after 70% partial hepatectomy (PHx) in rats. Celecoxib (20 mg/kg/day) and seratrodast (2 mg/kg/day) were given orally 1 h before PHx and then daily till the end of experiment (1, 3, or 7 days after the operation). Interestingly, celecoxib-treated rats showed a further increase in interleukin-6, p65 nuclear factor κB, and phosphorylated signal transducer and activator of transcription 3 as compared with PHx control rats. Furthermore, the liver contents of growth factors as well as β-catenin and cyclin D1protein expressions were also enhanced by celecoxib. Accordingly, celecoxib significantly improved hepatic proliferation as indicated by the increase in Ki67 expression and liver index. Contrariwise, seratrodast hindered the normal regeneration process and completely abolished the proliferative effect of celecoxib. In conclusion, TXA₂ has a major role in liver regeneration that could greatly mediate the triggering effect of celecoxib on hepatocytes proliferation following PHx.

Dynamics of Platelet Behaviors as Defenders and Guardians: Accumulations in Liver, Lung, and Spleen in Mice

Systemic platelet behaviors in experimental animals are often assessed by infusion of isotope-labeled platelets and measuring them under anesthesia. However, such procedures alter, therefore may not reveal, real-life platelet behaviors. 5-Hydroxytryptamine (5HT or serotonin) is present within limited cell-types, including platelets. In our studies, by measuring 5HT as a platelet-marker in non-anesthetized mice, we identified stimulation- and time-dependent accumulations in liver, lung, and/or spleen as important systemic platelet behaviors. For example, intravenous, intraperitoneal, or intragingival injection of lipopolysaccharide (LPS, a cell-wall component of Gram-negative bacteria), interleukin (IL)-1, or tumor necrosis factor (TNF)-α induced hepatic platelet accumulation (HPA) and platelet translocation into the sinusoidal and perisinusoidal spaces or hepatocytes themselves. These events occurred "within a few hours" of the injection, caused hypoglycemia, and exhibited protective or causal effects on hepatitis. Intravenous injection of larger doses of LPS into normal mice, or intravenous antigen-challenge to sensitized mice, induced pulmonary platelet accumulation (PPA), as well as HPA. These reactions occurred "within a few min" of the LPS injection or antigen challenge and resulted in shock. Intravenous injection of 5HT or a catecholamine induced a rapid PPA "within 6 s." Intravenous LPS injection, within a minute, increased the pulmonary catecholamines that mediate the LPS-induced PPA. Macrophage-depletion from liver and spleen induced "day-scale" splenic platelet accumulation, suggesting the spleen is involved in clearing senescent platelets. These findings indicate the usefulness of 5HT as a marker of platelet behaviors, and provide a basis for a discussion of the roles of platelets as both "defenders" and "guardians."

Exploiting the unique phenotypes of the earthworm Eudrilus eugeniae to evaluate the toxicity of chemical substances

Both the evaluation and the determination of toxicity of chemical substances present in the environment have implications in human health. In this present study, the natural phenomenon named autotomy, a self-defense mechanism employed by several animals against the toxic chemical contaminants, was considered to assess the toxicity of different chemical substances. We investigated the effects of glucose, sodium chloride, kanamycin, mercuric chloride, arsenic trioxide, and lead oxide on the phenotypes of earthworm Eudrilus eugeniae. Depending on the concentration of different chemicals, worms exhibit unique phenotypes. These phenotypes can be used to identify the toxicity as well as the toxic concentration of the chemicals. Upon exposure to toxic chemicals, worms use different mechanical forces at the site of cleavage furrow to detach its segments. During the detachment, there is no apparent blood loss at both the ends of the worm. Our results show that the mercuric chloride is toxic at the concentration above 5 μg when compared to other chemicals. Based on our findings, the toxic effects of a chemical and the toxic concentration of a chemical can be evaluated in both cost and time-efficient manner; in addition, these chemicals can be classified into the following categories: (1) mercuric chloride is extreme-toxic, (2) arsenic trioxide and lead oxide is toxic, (3) kanamycin and sodium chloride is low-toxic, and (4) glucose is non-toxic.

Liver dual arterial blood supply maintains liver regeneration: Analysis of signaling pathways in rats

Liver dual arterial blood supply (LDABS) could increase blood supply to the liver and maintain normal liver regeneration in patients with compromised portal vein. The current study attempted to examine the underlying molecular mechanisms. Male Sprague-Dawley rats randomly received partial hepatectomy (PH) alone or PH followed by LDABS. Liver regeneration was assessed by histological examination, liver function and liver regeneration rate (LRR). Whole-genome oligo microarray analysis was used to compare gene expression profile between rats receiving PH and rats receiving PH plus LDABS. Key genes identification was validated using a MAPK signaling polymerase chain reaction (PCR) array. The extent of liver regeneration in rats receiving PH plus LDABS was comparable to that in rats receiving PH alone. The differentially expressed genes were enriched in 12 signaling pathways in two groups. MAPK signaling pathway, NF-kappa B signaling pathway, and Toll-like receptor signaling pathway were involved in LDABS-mediated liver regeneration, with Retinoblastoma 1 (Rb1), Cyclin D1, Cyclin-dependent kinase 4, Mitogen-activated protein kinase 10 (Mapk10) and CAMP responsive element binding protein 1 genes in the initiation phase, Kirsten rat sarcoma viral oncogene homolog (Kras), tumor protein 53, MYC proto-oncogene, BHLH transcription factor, Cyclin E1 and Heat shock protein family B (small) member 1 genes in the proliferation phase, Kras, Rb1, Jun proto-oncogene, AP-1 transcription factor subunit, Cyclin D2 and Mapk10 genes in the termination phase were identified as key genes in LDABS-mediated liver regeneration using MAPK signaling PCR array analysis.

GABA and 5-HT chitosan nanoparticles decrease striatal neuronal degeneration and motor deficits during liver injury

The metabolic alterations resulted from hepatic injury and cell loss lead to synaptic defects and neurodegeneration that undoubtedly contribute motor deficits. In the present study, GABA and 5-HT chitosan nanoparticles mediated liver cell proliferation influenced by growth factor and cytokines and neuronal survival in corpus striatum of partially hepatectomised rats was evaluated. Liver cell proliferation was initiated and progressed by the combined effect of increased expression of growth factor, insulin like growth factor-1 and decreased expressions of cytokines, tumor necrosis factor-α and Akt-1. This was confirmed by the extent of incorporation of thymidine analogue, BrdU, in the DNA of rapidly dividing cells. Inappropriate influx of compounds to corpus striatum resulting from incomplete metabolism elevated GABAB and 5-HT2A neurotransmissions compared to those treated with nanoparticles. This directly influenced cyclic AMP response element binding protein, glial cell derived neurotrophic factor and brain derived neurotrophic factor in the corpus striatum that facilitate neurogenesis, neuronal survival, development, differentiation and neuroprotection. Motor deficits due to liver injury followed striatal neuronal damage were scored by grid walk and rotarod studies, which confirmed the regain of motor activity by GABA and 5-HT chitosan nanoparticle treatment. The present study revealed the therapeutic significance of GABA and 5-HT chitosan nanoparticles in liver based diseases and related striatal neuronal damage that influenced by GABA and 5-HT.

Platelet extracts induce growth, migration and invasion in human hepatocellular carcinoma in vitro

Background

Thrombocytopenia has been reported to be associated with small size HCCs, and thrombocytosis to be associated with large size HCCs. The aim was to examine the effects of platelets in relation to HCC cell growth.

Methods

The effects of time-expired pooled normal human platelets were examined on human HCC cell line growth and invasion.

Results

Blood platelet numbers increased with increasing HCC tumor size and portal vein invasion. Platelet extracts enhanced cell growth in 4 human HCC cell lines, as well as cell migration, medium AFP levels and decreased apoptosis. Cell invasion was significantly enhanced, using a Matrigel-coated trans-well membrane and3D (Real-Time Imaging) invasion assay. Western blots showed that platelets caused enhanced phospho-ERK and phospho–JNK signaling and anti-apoptotic effect with increase of Bcl-xL (anti-apoptotic marker) and decrease of Bid (pro-apoptotic marker) levels. Their growth effects were blocked by a JNK inhibitor.

Conclusions

Platelets stimulated growth and invasion of several HCC cell lines in vitro, suggesting that platelets or platelet growth factors could be a potential pharmacological target.