Growth or death? Control of cell destiny by mTOR and autophagy pathways

Angiotensin-converting enzyme 2 and AMPK/mTOR pathway in the treatment of liver fibrosis: Should we consider further implications?

This editorial contains comments on the article by Zhao et al in print in the World Journal of Gastroenterology. The mechanisms responsible for hepatic fibrosis are also involved in cancerogenesis. Here, we recapitulated the complexity of the renin-angiotensin system, discussed the role of hepatic stellate cell (HSC) autophagy in liver fibrogenesis, and analyzed the possible implications in the development of hepatocarcinoma (HCC). Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers definitively contribute to reducing hepatic fibrogenesis, whereas their involvement in HCC is more evident in experimental conditions than in human studies. Angiotensin-converting enzyme 2 (ACE2), and its product Angiotensin (Ang) 1-7, not only regulate HSC autophagy and liver fibrosis, but they also represent potential targets for unexplored applications in the field of HCC. Finally, ACE2 overexpression inhibits HSC autophagy through the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway. In this case, Ang 1-7 acts binding to the MasR, and its agonists could modulate this pathway. However, since AMPK utilizes different targets to suppress the mTOR downstream complex mTOR complex 1 effectively, we still need to unravel the entire pathway to identify other potential targets for the therapy of fibrosis and liver cancer.

The causes and consequences of trained immunity in myeloid cells

Conventionally, immunity in humans has been classified as innate and adaptive, with the concept that only the latter type has an immunological memory/recall response against specific antigens or pathogens. Recently, a new concept of trained immunity (a.k.a. innate memory response) has emerged. According to this concept, innate immune cells can exhibit enhanced responsiveness to subsequent challenges, after initial stimulation with antigen/pathogen. Thus, trained immunity enables the innate immune cells to respond robustly and non-specifically through exposure or re-exposure to antigens/infections or vaccines, providing enhanced resistance to unrelated pathogens or reduced infection severity. For example, individuals vaccinated with BCG to protect against tuberculosis were also protected from malaria and SARS-CoV-2 infections. Epigenetic modifications such as histone acetylation and metabolic reprogramming (e.g. shift towards glycolysis) and their inter-linked regulations are the key factors underpinning the immune activation of trained cells. The integrated metabolic and epigenetic rewiring generates sufficient metabolic intermediates, which is crucial to meet the energy demand required to produce proinflammatory and antimicrobial responses by the trained cells. These factors also determine the efficacy and durability of trained immunity. Importantly, the signaling pathways and regulatory molecules of trained immunity can be harnessed as potential targets for developing novel intervention strategies, such as better vaccines and immunotherapies against infectious (e.g., sepsis) and non-infectious (e.g., cancer) diseases. However, aberrant inflammation caused by inappropriate onset of trained immunity can lead to severe autoimmune pathological consequences, (e.g., systemic sclerosis and granulomatosis). In this review, we provide an overview of conventional innate and adaptive immunity and summarize various mechanistic factors associated with the onset and regulation of trained immunity, focusing on immunologic, metabolic, and epigenetic changes in myeloid cells. This review underscores the transformative potential of trained immunity in immunology, paving the way for developing novel therapeutic strategies for various infectious and non-infectious diseases that leverage innate immune memory.

Persistent β-Hexachlorocyclohexane Exposure Impacts Cellular Metabolism with a Specific Signature in Normal Human Melanocytes

BACKGROUND

Cutaneous melanoma arises from skin melanocytes and has a high risk of metastatic spread. Despite better prevention, earlier detection, and the development of innovative therapies, melanoma incidence and mortality increase annually. Major clinical risk factors for melanoma include fair skin, an increased number of nevi, the presence of dysplastic nevi, and a family history of melanoma. However, several external inducers seem to be associated with melanoma susceptibility such as environmental exposure, primarily unprotected sun experience, alcohol consumption, and heavy metals. In recent years, epidemiological studies have highlighted a potential risk of β-hexachlorocyclohexane (β-HCH), the most studied organochlorine pesticide, causing cancer induction including melanoma.

METHODS

We evaluated in vitro the impact of this pollutant on epidermal and dermal cells, attempting to describe mechanisms that could render cutaneous cells more prone to oncogenic transformation.

RESULTS

We demonstrated that β-HCH impacts melanocyte biology with a highly cell-type specific signature that involves perturbation of AKT/mTOR and Wnt/β-catenin signaling, and AMPK activation, resulting in lowering energy reserve, cell proliferation, and pigment production.

CONCLUSIONS

In conclusion, long-term exposure to persistent organic pollutants damages melanocyte metabolism in its function of melanin production with a consequent reduction of melanogenesis indicating a potential augmented skin cancer risk.

The relationship between subclinical hypothyroidism and invasive papillary thyroid cancer

Background

Subclinical hypothyroidism is the most common thyroid dysfunction. Approximately 10% of patients with thyroid cancer have subclinical hypothyroidism. There is a paucity of real-world studies examining the relationship between subclinical hypothyroidism and known correlates of invasiveness of papillary thyroid carcinoma (PTC).

Materials and methods

A retrospective cohort study of 13,717 patients with PTC was conducted. Odds ratios were calculated to assess the relationship between subclinical hypothyroidism and extrathyroidal extension (ETE) after adjusting for BMI and genders. The Cancer Genome Atlas (TCGA) data were utilized for the analysis of TSHR-associated pathways, while qRT-PCR was employed to validate the expression levels of pivotal genes in the relevant signaling pathways.

Results

In total, 13,717 PTC patients (10,769 women and 2,948 men; mean [SD] age, 42.90 [9.43] years) were included in the retrospective study. Subclinical hypothyroidism was an independent risk factor for ETE (OR adjusted, 1.168 [95% CI, 1.028-1.327]; P=0.017). In normal-weight patients, subclinical hypothyroidism was an independent risk factor for ETE (OR adjusted, 1.287 [95% CI, 1.089-1.520]; P=0.003). However, this risk was not observed in under-weight, overweight, and obese patients. Compared to females, subclinical hypothyroidism was a higher risk factor for ETE in male patients with normal body weight (OR male=2.363 vs. OR female=1.228). Subclinical hypothyroidism was found to be a significant risk factor for ETE in the subgroup of patients younger than 38 years old (OR1 adjusted, 1.382 [95% CI, 1.032-1.852], P=0.030). The findings from Gene Set Enrichment Analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed the involvement of the autophagy signaling pathway in TSHR/ETE/EMT regulation. Moreover, the gene expression levels demonstrated a concentration-dependent relationship between TSH intervention levels and the expression of key genes in the autophagy pathway of thyroid cancer cells.

Conclusion

Subclinical hypothyroidism was an independent risk factor for ETE in patients with PTC. This association was particularly significant in normal-weight and younger patients. The risk of ETE associated with subclinical hypothyroidism was higher in males compared to females. Our study indicates a potential involvement of the autophagy pathway in regulating the ETE phenotype in thyroid cancer, specifically in the context of subclinical hypothyroidism.