Glutamine metabolism modulates chondrocyte inflammatory response

  1. Manoj Arra
  2. Gaurav Swarnkar
  3. Naga Suresh Adapala
  4. Syeda Kanwal Naqvi
  5. Lei Cai
  6. Muhammad Farooq Rai
  7. Srikanth Singamaneni
  8. Gabriel Mbalaviele
  9. Robert Brophy
  10. Yousef Abu-Amer  Is a corresponding author
  1. Department of Orthopedic Surgery, Washington University School of Medicine, United States
  2. Department of Mechanical Engineering and Material Sciences, Washington University School of Medicine, United States
  3. Bone and Mineral Division, Department of Medicine, Washington University School of Medicine, United States
  4. Shriners Hospital for Children, United States
5 figures, 2 tables and 1 additional file

Figures

Figure 1 with 1 supplement
Chondrocytes rely upon glutamine for energy production.

(A–E) Primary murine chondrocytes were treated with IL-1β (10ng/mL) for 24hr. Gene expression of Gls2, Gdh, Gs, Eaat2, and Asct2 was measured by quantitative PCR. Results from n=6-10 independent biological samples (as depicted in individual panels). Unpaired Student’s T test was performed (A: **p=0.0011, B: p=0.375, C: *p=0.0227, D: ***p=0.0005, and E: ***p=0.0003). (F) Primary murine chondrocytes were cultured in media with 4mM glutamine and 0mM glutamine under constant glucose conditions. After 24hr, viability was measured by (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) (MTT) assay. Results from n=6 samples from one representative experiment. Unpaired Student’s T test was performed, ****p<0.0001. (G) Primary murine chondrocytes were treated with CB-839 (1uM). Intracellular glutamate was measured by luminescent assay (n=6). Unpaired Student’s T test was performed, ****p<0.0001. (H) Primary murine chondrocytes were treated with CB-839 and/or IL-1β for 24hr. Intracellular ATP was measured by luminescent assay. Results from one representative experiment (n=8). One-way ANOVA was performed followed by Tukey’s multiple comparisons test, ****p<0.0001. (I–L) Primary sternal chondrocytes were cultured in media containing glutamine or media without glutamine for 24hr. Cells were then treated with IL-1β (10ng/mL) for 24hr. All values were normalized to cell viability of treatments relative to untreated cells as measured by MTT assay. (I–J) Extracellular acidification rate (ECAR) measurement in glycolysis stress test (Injection 1: no treatment, Injection 2: glucose, Injection 3: oligomycin, and Injection 4: 2-DG) or (K–L) Oxygen consumption rate (OCR) measurement in MitoStress test (Injection 1: no treatment, Injection 2: oligomycin, Injection 3: Carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP), and Injection 4: antimycin A/rotenone) was performed on Seahorse Instrument. Measurements were performed every 6min with n=eight replicates per timepoint for each condition. Arrows represent injections timepoints. Graphs shown in Figure 1J and L are from a single timepoint. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. J:**p=0.0077 and ****p<0.0001; L:****p<0.0001.

Figure 1—figure supplement 1
Chondrocytes rely upon glutamine for energy production.

(A–D) Primary sternal chondrocytes were cultured in media containing glutamine with or without CB-839 (1mM). Cells were then treated with IL-1β (10ng/mL) for 24hr. All values were normalized to cell viability of treatments relative to untreated cells as measured by MTT assay. (A–B) Extracellular acidification rate (ECAR) measurement in glycolysis stress test (Injection 1: no treatment, Injection 2: glucose, Injection 3: oligomycin, and Injection 4: 2-DG) (n=8) or (C–D) Oxygen consumption rate (OCR) measurement in MitoStress test (Injection 1: no treatment, Injection 2: oligomycin, Injection 3: FCCP, and Injection 4: antimycin A/rotenone) was performed on Seahorse Instrument. Measurements were performed every 6 min with n=eight replicates per timepoint for each condition. Arrows represent injection timepoints. Graphs shown in Figure 1—figure supplement 1B and D are from a single timepoint. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. B: *p=0.012 and D: ****p<0.0001. (E–J) Human chondrocytes were isolated from osteoarthritis (OA) cartilage or healthy cartilage isolated from patients. Gene expression was measured by quantitative PCR (qPCR) (n=8). (K–M) Human chondrocytes were isolated from knee cartilage and cultured in media. Cells were treated with IL-1β for 24 hr. Gene expression was measured by qPCR from n=8 biological samples. Unpaired Student’s T test was performed. I:**p=0.0013, J:**p=0.0032, and M:*p=0.05.

Figure 2 with 1 supplement
Glutamine deprivation causes metabolic reprogramming to inhibit glycolysis.

(A–C) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr. Gene expression of G6pd2, Eno1, and Ldha was measured by quantitative PCR from n=6 replicates. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. A: *p=0.0242, ****p<0.0001, B: ****p<0.0001, and C: ****p<0.0001. (D–K) Under similar conditions, metabolite levels were measured by Liquid chromatography–mass spectrometry (LC-MS) with n=3 replicates. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. D: ***p=0.0003, E:***p=0.0006, F: p>0.05, G: p>0.05, H:*p=0.036, I: **p=0.0012, J:**p=0.0079, and K: **p=0.009.

Figure 2—figure supplement 1
Glutamine deprivation causes metabolic reprogramming to inhibit glycolysis.

(A–E) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr. Gene expression of Gls, Got2, Idh2, Mdh, and Sdha was measured by quantitative PCR (qPCR) from n=6 replicates. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. A: **p=0.0085 and ***p<0.0004; B: **p=0.0011; C: ****p<0.0001 and ***p=0.0003; D:*p=0.036; E:***p=0.0005. (F) Under similar conditions, supernatant was collected, and lactic acid was measured. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ****p<0.0001. (G) Gene expression of Psat1 was measured under similar conditions by qPCR. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ***p=0.0006.

Figure 3 with 1 supplement
Glutamine deprivation inhibits the inflammatory response.

(A–B) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr. Gene expression of Il6 and Mmp13 was measured by quantitative PCR (qPCR). One-way ANOVA was performed followed by Tukey’s multiple comparisons test. A:****p<0.0001 (n=16) and B: *p=0.0489 (n=6). (C) Primary murine chondrocytes were isolated from NF-κB-luciferase reporter mice. Chondrocytes were then cultured in media containing 4 mM, 2 mM, or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β for 24 hr. NF-κB activity was measured by luciferase assay. n=4. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ****p<0.0001. (D) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were treated with IL-1β for the indicated timepoints. IκB-ζ protein (85kDa) was measured by immunoblotting, with actin (42kDa) used as housekeeping. Image displays representative experiment. (E) Primary murine chondrocytes were cultured in media containing 4mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr. ROS levels were measured by 2’,7’ –dichlorofluorescin diacetate (DCFDA) assay using microplate reader. n=6. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ****p<0.0001. (F) Primary chondrocytes were cultured in media containing glutamine and supplemented with ammonium chloride at the indicated concentrations for 24 hr in the presence of IL-1β. IκB-ζ protein was measured by immunoblotting. (G–H) Primary chondrocytes were cultured in media containing 4 mM or 0 mM glutamine for 6 hr. Cells were then supplemented with or without 2 mM ammonium chloride. IL-1β stimulation was performed for 24 hr. Gene expression of Il6 and Mmp13 was measured by qPCR. n=4. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. G: ****p<0.0001, **p=0.0065, and H: **p=0.0096, ***p=0.0005.

Figure 3—figure supplement 1
Glutamine deprivation inhibits the inflammatory response.

(A) Primary murine chondrocytes were treated with IL-1β in the presence or absence of CB-839 (1 mM) for 24 hr. Gene expression of Il6 was measured by quantitative PCR (qPCR). Results are representative of one experiment. n=4. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ****p<0.0001. (B) Under similar conditions, IκB-ζ protein (85kDa) levels were measured by immunoblotting. (C) Primary NF-κB-luciferase reporter chondrocytes were treated with IL-1β in the presence or absence of CB-839 (1 mM) for 24 hr. NF-κB activity was measured by luciferase assay. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ***p=0.0007 (D) Primary NF-κB-luciferase reporter chondrocytes were treated with IL-1β in the presence or absence of ammonium chloride (2 mM) or glutamate (200 μM). NF-κB activity was measured by luminescent luciferase assay. n=8. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ****p<0.0001. (E) Primary chondrocytes were cultured in media containing 4 mM or 0 mM glutamine for 6 hr. Cells were then supplemented with or without asparagine (1 mM) dissolved in PBS (IL-1β stimulation was performed for 24 hr). Gene expression of Il6 was measured by qPCR. n=4. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. p>0.05. (F) Chondrocytes were treated with IL-1β in the presence or absence of Epigallocatechin 3-gallate (ECGC) for 24 hr. Gene expression of Il6 was measured by qPCR. Results are representative of one experiment. n=4. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ****p<0.0001.

Figure 4 with 1 supplement
Glutamine deprivation promotes autophagy, and ammonia inhibits autophagy.

(A) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) in the presence or absence of chloroquine (10 μM) for 24 hr. Protein expressions of p62 (62kDa) and LC3-II (17kDa) were measured by immunoblotting, with representative image displayed. Bands quantified in supplemental figure. (B) Primary murine chondrocytes were plated on coated cover slips cultured in glutamine containing or glutamine free media for 12 hr. Cells were treated with chloroquine (10 μM) for 6 hr. Cells were fixed with 4% formaldehyde in PBS, and immunofluorescence (IF) was performed for LC3B and p62. Cells were mounted on slides and imaged with representative images displayed. (C) Primary chondrocytes were cultured in media containing 4 mM or 0 mM glutamine. Cells were supplemented with ammonium chloride at the indicated concentrations. After 6 hr, cells were treated with IL-1β (10 ng/mL) for 24 hr. Immunoblotting was performed for p62 and LC3B to display autophagosome processing. Image displays representative experiment. Bands quantified in supplemental figure. (D) Primary chondrocytes were cultured in media containing 4 mM or 0 mM glutamine. Cells were supplemented with glutamate (200 μM). After 6 hr, cells were treated with IL-1β (10 ng/mL) for 24 hr. Immunoblotting was performed for p62 and LC3b. Image displays representative experiment. Bands quantified in supplemental figure. (E) Primary murine chondrocytes were plated on coated cover slips cultured in glutamine containing or glutamine free media for 12 hr. Cells were supplemented with ammonium chloride (2 mM) or glutamate (200 μM). Cells were fixed with 4% formaldehyde, and IF was performed for LC3b and p62. Cells were mounted on slides and imaged with representative images to display autophagosome punctate.

Figure 4—figure supplement 1
Glutamine deprivation promotes autophagy, and ammonia inhibits autophagy.

(A–B) Quantification of western blot image displayed in Figure 4A. p62 pixel intensity and actin pixel intensity were measured. Each lane is represented as the ratio of p62/actin pixel density. A similar measurement was taken of LC3-I and LC3-II, with ratio of LC3-1/LC3-II represented for each lane.

(C–D) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr. Gene expression of Map1lc3b and Sqstm1 was measured by quantitative PCR (qPCR). Results from five to six biological replicates. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. (E–F) Chondrocytes were plated in glutamine-free media for different amounts of time. Gene expression of Map1lc3b and Sqstm1 was measured by qPCR. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. ***p=0.0004. (G) Under similar conditions, immunoblotting was performed for LC3 and p62. (H) Chondrocytes were treated with IL-1β in the presence or absence of CB-839 for 24 hr. Immunoblotting was performed for LC3. (I) Primary chondrocytes were cultured in media containing 4 mM or 0 mM glutamine. Cells were supplemented with ammonium chloride (2 mM) or glutamate (200 μM). After 6 hr, cells were treated with IL-1β (10 ng/mL) for 24 hr. Immunoblotting was performed for p62 and LC3B. Image displays representative experiment. (J–K) Quantification of western blot image displayed in Figure 4C. p62 pixel intensity and actin pixel intensity were measured. Each lane is represented as the ratio of p62/actin pixel density. A similar measurement was taken of LC3-I and LC3-II, with ratio of LC3-1/LC3-II represented for each lane. (L–M) Quantification of western blot image displayed in Figure 4D. p62 pixel intensity and actin pixel intensity were measured. Each lane is represented as the ratio of p62/actin pixel density. A similar measurement was taken of LC3-I and LC3-II, with ratio of LC3-1/LC3-II represented for each lane. (N) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr. Gene expression of Atf4 was measured by qPCR. Results from n=4 replicates. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. **p=0.0033 and **p=0.0088. (O) Immunoblotting was performed under similar conditions for ATF4 (38kDa). Fold change is listed above the lanes, normalized to actin. (P) Chondrocytes were plated in glutamine-free media for different amounts of time. Gene expression of Atf4 was measured by qPCR. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. *p=0.0419 and ***p=0.0001. (Q) Meniscal-ligamentous injury (MLI) surgery was performed on 12-week-old mice to induce osteoarthritis (OA) with sham surgery performed on contralateral leg. After 2 weeks, knee joints were collected and sectioned. Immunohistochemistry (IHC) was performed for ATF4 which is display as brown stain, with representative image displayed.

Figure 5 with 1 supplement
Glutamine deprivation modulates mTOR activation.

(A) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL). After 24 hr, lysates were collected, and immunoblotting was performed for pAKT (60kDa) and total Akt (58kDa). (B) Under similar conditions, immunoblotting was performed for pS6 and total S6 (32kDa). (C–D) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) in the presence or absence of rapamycin 50 nM for 24 hr. Gene expression of Il6 and Mmp13 was measured by quantitative PCR. Results from one representative experiment. n=4. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. C:****p<0.0001.

Figure 5—figure supplement 1
Glutamine deprivation modulates mTOR activation.

(A) Primary murine chondrocytes were cultured in media containing 4 mM glutamine or 0 mM glutamine for 24 hr. Cells were then treated with IL-1β (10 ng/mL) for 24 hr in the presence or absence of rapamycin (50 nM). Immunoblotting was performed for pS6 and total S6 (32kDa). (B–E) Under similar conditions, gene expression was measured by quantitative PCR. One-way ANOVA was performed followed by Tukey’s multiple comparisons test. B:****p<0.0001, C: **p=0.0017, and D:**p=0.0088. n=4.

Tables

Key resources table
Reagent type (species) or resourceDesignationSource or referenceIdentifiersAdditional information
Genetic reagent (Mus, musculus)C57BL/6miceJackson LabsRRID:IMSR_JAX:000664
Genetic reagent (Mus, musculus)NF-kB luciferase reporter miceJackson LabsRRID:IMSR_JAX:027529
Biological sample (human)Human osteoarthritis chondrocytesIsolated from discarded human tissues, Arra et al., 2020
Biological sample (mouse)Murine chondrocytesIsolated from sterna of newborn pups of genetic strains indicated above, Arra et al., 2020
AntibodyAnti-ATF4 (rabbit polyclonal)ThermoFisher10835–1-AP, RRID:AB_20586001:1,000 for Western blot
AntibodyBiotinylated secondary (horse anti-rabbit polyclonal)Vector BiolabsBP-11001:1,000 for IHC
AntibodyAnti-LC3b (rabbit polyclonal)Cell Signaling Technology2775, RRID:AB_9159501:1,000 Western blot; 1:100 for IF
AntibodyAnti-p62 (mouse monoclonal)Abnova2C11, RRID:AB_4370851:1,000 Western blot; 1:100 for IF
AntibodyAnti-IkB-z (rat monoclonal)Invitrogen14-16801-82, RRID:AB_112180831:1,000 Western blot
AntibodyAnti-p-Akt (rabbit polyclonal)Cell Signaling Technology9271, RRID:AB_3298251:1,000 Western blot
AntibodyAnti-Akt (rabbit polyclonal)Cell Signaling Technology9272, RRID:AB_3298271:1,000 Western blot
AntibodyAnti-p-S6 (rabbit polyclonal)Cell Signaling Technology2211, RRID:AB_3316791:1,000 Western blot
AntibodyAnti-S6 (rabbit polyclonal)Cell Signaling Technology2217, RRID:AB_3313551:1,000 Western blot
AntibodyAnti-Actin (mouse monoclonal)Sigma-AldrichA2228, RRID:AB_4766971:10,000 Western blot
Sequence-based reagentquantitative PCR primersIntegrated DNA technologiesN/ACustom DNA oligos
Peptide, recombinant proteinCollagenase DRocheCOLLD-RO
Peptide, recombinant proteinPronaseRochePRON-RO
Peptide, recombinant proteinIL-1bPeprotech211-11B10ng/mL
Commercial assay or kitDiaminobenzidine (DAB) peroxidase kitVector BiolabsSK4100
Commercial assay or kitLactate assay kitEton Biosciences1.2E+09
Commercial assay or kitPurelink RNA Mini KitAmbion12183025
Commercial assay or kitHigh capacity cDNA Reverse Transcription KitApplied Biosystems4368814
Commercial assay or kitATP assay kitBiovisionK255
Commercial assay or kitLuminescence assay kitGoldBioI-930
Commercial assay or kitGlutamate-Glo Assay kitPromegaJ7021
Chemical compound and drugsCB-839SelleckS7655
Chemical compound and drugsRapamycinMedChem ExpressHY-10219
Chemical compound and drugsAmmonium ChlorideSigma-AldrichA9434
Chemical compound and drugsL-glutamic acidSigma-AldrichG1626
Chemical compound and drugsStreptavidin Horseradish peroxidase (HRP)Vector BiolabsSA-5004–1
Chemical compound and drugsDAPICell Signaling Technology9071
Chemical compound and drugsTrizolThermoFisher15596026
Chemical compound and drugsDCFDASigma-AldrichD6883
Chemical compound and drugsMTTSigma-AldrichM655
Chemical compound and drugsImmunocalFisher ScientificNC9044643
Chemical compound and drugsiTaq universal SYBR GreenBioRad1725120
Software and algorithmGen5 softwareAgilent BioTekBTGENSCPRIM
Software and algorithmPrismGraphpadRRID:SCR_002798
Software and algorithmWaveAgilent BioTekRRID:SCR_014526
Table 1
List of primers.
PrimerSequence (5’→3’)
m-Il6GCTACCAAACTGGATATAATCAGGA
CCAGGTAGCTATGGTACTCCAGAA
m-Mmp13GCCAGAACTTCCCAACCAT
TCAGAGCCCAGAATTTTCTCC
m-Atf4TCGATGCTCTGTTTCGAATG
AGAATGTAAAGGGGGCAACC
m-Lc3TGGGACCAGAAACTTGGTCT
GACCAGCACCCCAGTAAGAT
m-p62AGAATGTGGGGGAGAGTGTG
TCTGGGGTAGTGGGTGTCAG
m-GLSCTACAGGATTGCGAACATCTGAT
ACACCATCTGACGTTGTCTGA
m-GDHGGCCGATTGACCTTCAAATA
TCCTGTCCTGGAACTCTGCT
m-GSCATTGACAAACTGAGCAAGAGG
AAGTCGTTGATGTTGGAGGTT
m-EAAT2GGCAATCCCAAACTCAAGAA
GTGCTATTGGCCTCCTCAGA
m-ASCT2CAACCAAAGAGGTGCTGGAT
CCTCCACCTCACAGAGAAGC
m-G6pd2CTGAATGAACGCAAAGCTGA
CAATCTTGTGCAGCAGTGGT
m-Eno1GCCTCCTGCTCAAAGTCAAC
AACGATGAGACACCATGACG
m-LdhaTGGAAGACAAACTCAAGGGCGAGA
TGACCAGCTTGGAGTTCGCAGTTA
m-MdhGGTGCAGCCTTAGATAAATACGC
AGTCAAGCAACTGAAGTTCTCC
m-SdhaAACACTGGAGGAAGCACACC
AGTAGGAGCGGATAGCAGGA
m-Idh2AACCGTGACCAGACTGATGAC
ATGGTGGCACACTTGACAGC
m-Got2GATCCGTCCCCTGTATTCCA
CACCTCTTGCAACCATTGCTT
h-GLS2TCTCTTCCGAAAGTGTGTGAGC
CCGTGAACTCCTCAAAATCAGG
h-GLUD1TATCCGGTACAGCACTGACG
GCTCCATGGTGAATCTTCGT
h-GSCCTGCTTGTATGCTGGAGTC
GATCTCCCATGCTGATTCCT
h-GOT2GTTTGCCTCTGCCAATCATATG
GAGGGTTGGAATACATGGGAC
h-NFKBIZCCGTTTCCCTGAACACAGTT
AGAAAAGACCTGCCCTCCAT
h-MMP3CTGGACTCCGACACTCTGGA
CAGGAAAGGTTCTGAACTGACC
h-ATF4TCTCCAGCGACAAGGCTAA
CAATCTGTCCCGGAGAAGG

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  1. Manoj Arra
  2. Gaurav Swarnkar
  3. Naga Suresh Adapala
  4. Syeda Kanwal Naqvi
  5. Lei Cai
  6. Muhammad Farooq Rai
  7. Srikanth Singamaneni
  8. Gabriel Mbalaviele
  9. Robert Brophy
  10. Yousef Abu-Amer
(2022)
Glutamine metabolism modulates chondrocyte inflammatory response
eLife 11:e80725.
https://doi.org/10.7554/eLife.80725