Journal: American journal of physiology. Cell physiology

Article Title: Nicotinamide N-methyltransferase upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes.

doi: 10.1152/ajpcell.00195.2021

Figure Lengend Snippet: Figure 4. mTORC1 activation is an upstream event in palmitate induced ATF4 activation. A: AML12 cells were pretreated with or without Torin1 (0.25 mM) or rapamycin (Rapa at 50 nM) for 2 h before palmitate (0.4 mM) exposure for 16 h. Total protein was extracted. Protein abundance of ATF4 and actin were detected by Western blotting. The signal of ATF4 protein band was measured by densitometry and then divided by the sig- nal of its corresponding actin abundance in the same sample. Data are expressed as means ± SD, n = 3 separate experiments. Student’s t test was used for statistical evaluation (P < 0.001 vs. control). B: AML12 were pretreated with Torin1 (0.25 mM) for 2 h before a 16-h palmitate (0.4 mM) exposure. Total RNA was extracted. ATF4 mRNA levels were detected by real time-qPCR. Data are expressed as means ± SD, n = 4 sep- arated experiments. Differences between the two groups were deter- mined using Student’s t test (P < 0.001 vs. control). ATF, activating transcription factor.

Article Snippet: Cells were grown at 80% confluence before the exposure of treatments in various experiments. siRNA Transfection Cultured AML12 hepatocytes were transfected with mouse ATF4 siRNA (Santa Cruz, sc-35113).

Techniques: Activation Assay, Quantitative Proteomics, Western Blot, Control

Journal: American journal of physiology. Cell physiology

Article Title: Nicotinamide N-methyltransferase upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes.

doi: 10.1152/ajpcell.00195.2021

Figure Lengend Snippet: Figure 5. mTORC1 activation contributes to palmi- tate-induced ER stress and NNMT upregulation. A and B: AML12 cells were pretreated with Torin1 (0.25 mM) for 2 h before the palmitate (0.4 mM) exposure for 16 h. Total RNA was extracted. The gene expres- sions of Xbp1, Xbp1s, and Xbp1u were quantified by real time-qPCR and Xbp1s/Xbp1u ratio calculated. Data are expressed as means ± SD, n = 4 different experiments. Differences between the two groups were determined using Student’s t test (P < 0.001vs. control). C: AML12 cells were pretreated with Tornin1 for 2 h before tunicamycin (10 μm) treat- ment for 16 h. Protein abundance of p-S6 and actin was detected by Western blotting. The signal of p-S6 protein band was measured by densitometry and then divided by the signal of its corresponding actin abundance in the same sample. Data are expressed as means ± SD, n = 5 separate experiments. Student’s t test was used for statistical evaluation (P < 0.01; P < 0.0001 vs. control). D: Ten- week-old male C57BL/6N mice were injected with tunicamycin (2 mg/kg body wt ip) or isovolumic vehi- cle (150 mM dextrose) and 16 h later livers were har- vested. Protein abundance of ATF4, p-S6 and actin was detected by Western blotting. E: AML12 cells were pretreated with Torin1 (0.25 mM) for 2 h before tunicamycin (10 μm) treatment for 16 h. Protein abun- dance of ATF4 was detected by Western blotting. F: AML12 cells were pretreated with Torin1 for 2 h before tunicamycin (10 μm) treatment for 16 h. Total RNA was extracted and NNMT gene expression quantified by real time-qPCR. All data were expressed as means ± SD, n = 4 separated experiments. Differences between the two groups were determined using Student’s t test (P < 0.01; P < 0.001; P < 0.0001 vs. control). NNMT, nicotinamide N-methyl- transferase; XBP1, X-box binding protein 1.

Article Snippet: Cells were grown at 80% confluence before the exposure of treatments in various experiments. siRNA Transfection Cultured AML12 hepatocytes were transfected with mouse ATF4 siRNA (Santa Cruz, sc-35113).

Techniques: Activation Assay, Control, Quantitative Proteomics, Western Blot, Injection, Gene Expression, Binding Assay

Journal: American journal of physiology. Cell physiology

Article Title: Nicotinamide N-methyltransferase upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes.

doi: 10.1152/ajpcell.00195.2021

Figure Lengend Snippet: Figure 6. NNMT inhibition protects against palmitate-induced cell death. A: AML12 cells were pretreated with either JBSNF-000088 (20 mM) or II399 (20 mM) at the indicated concentrations for 4 h before palmitate (0.4 mM) exposure for 16 h. Cell viability was determined by LDH release mea- surement. Data are expressed as mean ± SD, n = 3 separated experi- ments. Bars with different character differ significantly (P < 0.05). B: AML12 cells were transfected with either scramble siRNA or NNMT siRNA for 24 h and treated with palmitate at 0.4 mM for 16 h. Cell death was determined by LDH release measurement. Data are expressed as means ± SD, n = 3 separated experiments. Differences between the two groups were determined using Student’s t test (P < 0.01; P < 0.001; P < 0.001 vs. control). NNMT, nicotinamide N-methyltransferase.

Article Snippet: Cells were grown at 80% confluence before the exposure of treatments in various experiments. siRNA Transfection Cultured AML12 hepatocytes were transfected with mouse ATF4 siRNA (Santa Cruz, sc-35113).

Techniques: Inhibition, Transfection, Control

Journal: American journal of physiology. Cell physiology

Article Title: Nicotinamide N-methyltransferase upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes.

doi: 10.1152/ajpcell.00195.2021

Figure Lengend Snippet: Figure 7. Protein kinase A (PKA) inhibition compro- mises the protective effect of NNMT inhibition against palmitate-induced cell death. A and B: AML12 cells were treated with either JBSNF-000088 (25 mM) or II399 (25 mM) for 6 h. Total proteins were isolated and PKA substrates detected by Western blotting. The signal of PKS substrates was measured by densitometry and then divided by the signal of its corresponding actin abundance in the same sample. Data are expressed as means ± SD, n = 3 separate experiments. Student’s t test was used for statistical evaluation (P < 0.05; P < 0.01 vs. untreated cells). C: AML12 cells were pretreated with either JBSNF-000088 (25 mM) or II399 (25 mM) at the pres- ence/absence of PKA inhibitor, either SQ22536 (200 mM) or H89 (10 mM) for 4 h before palmitate exposure for 16 h. Cell death was determined by LDH release. All data are expressed as means ± SD, n = 3 sepa- rated experiments. Differences between the two groups were determined using Student’s t test (P < 0.05; P < 0.01; P < 0.001 vs control). D: sche- matic illustration of the role and mechanism of NNMT upregulation in palmitate-induced hepatocyte lipotox- icity. The mTORC1-ATF4 pathway activation contrib- utes to palmitate-elicited NNMT upregulation and protein kinase A (PKA) activation contributes to NNMT inhibition-conferred protection against hepatolipotox- icity. NNMT, nicotinamide N-methyltransferase.

Article Snippet: Cells were grown at 80% confluence before the exposure of treatments in various experiments. siRNA Transfection Cultured AML12 hepatocytes were transfected with mouse ATF4 siRNA (Santa Cruz, sc-35113).

Techniques: Inhibition, Isolation, Western Blot, Control, Activation Assay