Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs
Abstract Background Intervertebral disc degeneration contributes to low back pain. The avascular intervertebral disc consists of a central hypoxic nucleus pulpous (NP) surrounded by the more oxygenated annulus fibrosus (AF). Lactic acid, an abundant end-product of NP glycolysis, has long been viewed...
| Main Authors: | , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
BMC
2021-05-01
|
| Series: | Arthritis Research & Therapy |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s13075-021-02501-2 |
| _version_ | 1818455053398179840 |
|---|---|
| author | Dong Wang Robert Hartman Chao Han Chao-ming Zhou Brandon Couch Matias Malkamaki Vera Roginskaya Bennett Van Houten Steven J. Mullett Stacy G. Wendell Michael J. Jurczak James Kang Joon Lee Gwendolyn Sowa Nam Vo |
| author_facet | Dong Wang Robert Hartman Chao Han Chao-ming Zhou Brandon Couch Matias Malkamaki Vera Roginskaya Bennett Van Houten Steven J. Mullett Stacy G. Wendell Michael J. Jurczak James Kang Joon Lee Gwendolyn Sowa Nam Vo |
| author_sort | Dong Wang |
| collection | DOAJ |
| description | Abstract Background Intervertebral disc degeneration contributes to low back pain. The avascular intervertebral disc consists of a central hypoxic nucleus pulpous (NP) surrounded by the more oxygenated annulus fibrosus (AF). Lactic acid, an abundant end-product of NP glycolysis, has long been viewed as a harmful waste that acidifies disc tissue and decreases cell viability and function. As lactic acid is readily converted into lactate in disc tissue, the objective of this study was to determine whether lactate could be used by AF cells as a carbon source rather than being removed from disc tissue as a waste byproduct. Methods Import and conversion of lactate to tricarboxylic acid (TCA) cycle intermediates and amino acids in rabbit AF cells were measured by heavy-isotope (13C-lactate) tracing experiments using mass spectrometry. Levels of protein expression of lactate converting enzymes, lactate importer and exporter in NP and AF tissues were quantified by Western blots. Effects of lactate on proteoglycan (35S-sulfate) and collagen (3H-proline) matrix protein synthesis and oxidative phosphorylation (Seahorse XFe96 Extracellular Flux Analyzer) in AF cells were assessed. Results Heavy-isotope tracing experiments revealed that AF cells imported and converted lactate into TCA cycle intermediates and amino acids using in vitro cell culture and in vivo models. Addition of exogenous lactate (4 mM) in culture media induced expression of the lactate importer MCT1 and increased oxygen consumption rate by 50%, mitochondrial ATP-linked respiration by 30%, and collagen synthesis by 50% in AF cell cultures grown under physiologic oxygen (2-5% O2) and glucose concentration (1-5 mM). AF tissue highly expresses MCT1, LDH-H, an enzyme that preferentially converts lactate to pyruvate, and PDH, an enzyme that converts pyruvate to acetyl-coA. In contrast, NP tissue highly expresses MCT4, a lactate exporter, and LDH-M, an enzyme that preferentially converts pyruvate to lactate. Conclusions These findings support disc lactate-dependent metabolic symbiosis in which lactate produced by the hypoxic, glycolytic NP cells is utilized by the more oxygenated AF cells via oxidative phosphorylation for energy and matrix production, thus shifting the current research paradigm of viewing disc lactate as a waste product to considering it as an important biofuel. These scientifically impactful results suggest novel therapeutic targets in disc metabolism and degeneration. |
| first_indexed | 2024-12-14T22:04:39Z |
| format | Article |
| id | doaj.art-c277863dd836412d934d854ba2944040 |
| institution | Directory Open Access Journal |
| issn | 1478-6362 |
| language | English |
| last_indexed | 2024-12-14T22:04:39Z |
| publishDate | 2021-05-01 |
| publisher | BMC |
| record_format | Article |
| series | Arthritis Research & Therapy |
| spelling | doaj.art-c277863dd836412d934d854ba29440402022-12-21T22:45:54ZengBMCArthritis Research & Therapy1478-63622021-05-0123111510.1186/s13075-021-02501-2Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discsDong Wang0Robert Hartman1Chao Han2Chao-ming Zhou3Brandon Couch4Matias Malkamaki5Vera Roginskaya6Bennett Van Houten7Steven J. Mullett8Stacy G. Wendell9Michael J. Jurczak10James Kang11Joon Lee12Gwendolyn Sowa13Nam Vo14Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Pharmacology and Chemical Biology, University of PittsburghDepartment of Pharmacology and Chemical Biology, University of PittsburghDepartment of Pharmacology and Chemical Biology, University of PittsburghDepartment of Pharmacology and Chemical Biology, University of PittsburghDepartment of Medicine, Division of Endocrinology and Metabolism, University of PittsburghDepartment of Orthopedics, Brigham and Women’s Hospital, School of Medicine, Harvard UniversityDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghDepartment of Orthopaedic Surgery, Ferguson Laboratory for Orthopedic and Spine Research, University of PittsburghAbstract Background Intervertebral disc degeneration contributes to low back pain. The avascular intervertebral disc consists of a central hypoxic nucleus pulpous (NP) surrounded by the more oxygenated annulus fibrosus (AF). Lactic acid, an abundant end-product of NP glycolysis, has long been viewed as a harmful waste that acidifies disc tissue and decreases cell viability and function. As lactic acid is readily converted into lactate in disc tissue, the objective of this study was to determine whether lactate could be used by AF cells as a carbon source rather than being removed from disc tissue as a waste byproduct. Methods Import and conversion of lactate to tricarboxylic acid (TCA) cycle intermediates and amino acids in rabbit AF cells were measured by heavy-isotope (13C-lactate) tracing experiments using mass spectrometry. Levels of protein expression of lactate converting enzymes, lactate importer and exporter in NP and AF tissues were quantified by Western blots. Effects of lactate on proteoglycan (35S-sulfate) and collagen (3H-proline) matrix protein synthesis and oxidative phosphorylation (Seahorse XFe96 Extracellular Flux Analyzer) in AF cells were assessed. Results Heavy-isotope tracing experiments revealed that AF cells imported and converted lactate into TCA cycle intermediates and amino acids using in vitro cell culture and in vivo models. Addition of exogenous lactate (4 mM) in culture media induced expression of the lactate importer MCT1 and increased oxygen consumption rate by 50%, mitochondrial ATP-linked respiration by 30%, and collagen synthesis by 50% in AF cell cultures grown under physiologic oxygen (2-5% O2) and glucose concentration (1-5 mM). AF tissue highly expresses MCT1, LDH-H, an enzyme that preferentially converts lactate to pyruvate, and PDH, an enzyme that converts pyruvate to acetyl-coA. In contrast, NP tissue highly expresses MCT4, a lactate exporter, and LDH-M, an enzyme that preferentially converts pyruvate to lactate. Conclusions These findings support disc lactate-dependent metabolic symbiosis in which lactate produced by the hypoxic, glycolytic NP cells is utilized by the more oxygenated AF cells via oxidative phosphorylation for energy and matrix production, thus shifting the current research paradigm of viewing disc lactate as a waste product to considering it as an important biofuel. These scientifically impactful results suggest novel therapeutic targets in disc metabolism and degeneration.https://doi.org/10.1186/s13075-021-02501-2LactateLactic acidIntervertebral discAnnulus fibrosusNucleus pulpousGlycolysis |
| spellingShingle | Dong Wang Robert Hartman Chao Han Chao-ming Zhou Brandon Couch Matias Malkamaki Vera Roginskaya Bennett Van Houten Steven J. Mullett Stacy G. Wendell Michael J. Jurczak James Kang Joon Lee Gwendolyn Sowa Nam Vo Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs Arthritis Research & Therapy Lactate Lactic acid Intervertebral disc Annulus fibrosus Nucleus pulpous Glycolysis |
| title | Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs |
| title_full | Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs |
| title_fullStr | Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs |
| title_full_unstemmed | Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs |
| title_short | Lactate oxidative phosphorylation by annulus fibrosus cells: evidence for lactate-dependent metabolic symbiosis in intervertebral discs |
| title_sort | lactate oxidative phosphorylation by annulus fibrosus cells evidence for lactate dependent metabolic symbiosis in intervertebral discs |
| topic | Lactate Lactic acid Intervertebral disc Annulus fibrosus Nucleus pulpous Glycolysis |
| url | https://doi.org/10.1186/s13075-021-02501-2 |
| work_keys_str_mv | AT dongwang lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT roberthartman lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT chaohan lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT chaomingzhou lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT brandoncouch lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT matiasmalkamaki lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT veraroginskaya lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT bennettvanhouten lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT stevenjmullett lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT stacygwendell lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT michaeljjurczak lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT jameskang lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT joonlee lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT gwendolynsowa lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs AT namvo lactateoxidativephosphorylationbyannulusfibrosuscellsevidenceforlactatedependentmetabolicsymbiosisinintervertebraldiscs |