Oral Fluid Inflammatory Biomarker Profile in LC: Evaluation of Oral Active and Total MMP-8, MMP-9, and TIMP-1 in Relation to BMI…, 2026, Seno Aji+

[Chandelier]

Oral Fluid Inflammatory Biomarker Profile in Long COVID: Evaluation of Oral Active and Total MMP-8, MMP-9, and TIMP-1 in Relation to BMI and Disease Status

Spoiler: Authors

Seno Aji, Nur Rahman Ahmad; Thomas, Julie Toby; Tervahartiala, Taina; Räisänen, Ismo T.; Varonen, Mikko; Liira, Helena; Kanerva, Mari; Vangelova-Korpinen, Velina; Sorsa, Timo; Välimaa, Hanna

Abstract​

Background​

Long COVID (LC) is characterized by persistent systemic symptoms, but its oral inflammatory profile remains unclear. This study evaluated oral inflammatory biomarkers, particularly matrix metalloproteinase (MMP) -8, -9 and their regulators in oral rinse samples from LC patients.

Methods​

This cross-sectional study analyzed oral rinse samples from 115 LC patients and 103 comparable controls. Periodontal inflammation was screened using a chair-side active MMP-8 (aMMP-8) point-of-care test (POCT). Biomarkers (aMMP-8, total MMP-8, MMP-9, TIMP-1, and MPO) were quantified and validated by Western blotting and gelatin zymography. Associations with LC and clinical variables were assessed using bivariate analysis and multivariable regression.

Results​

LC patients had significantly higher total MMP-8, MMP-9, TIMP-1, and MMP-9/TIMP-1 ratio (all p<0.05 in both analyses). IFMA-measured active MMP-8 became independently associated with LC after multivariable adjustment.

Chair-side aMMP-8 POCT showed a non-significant trend toward higher positivity in LC (16.5% vs. 8.7%). BMI was positively associated with aMMP-8, tMMP-8 and tMMP-8/TIMP-1 molar ratio. Antidepressant use was associated with tMMP-8/TIMP-1 molar ratio. Western blotting confirmed active MMP-8 species and gingipain.

Conclusion​

These findings suggest an altered oral inflammatory biomarker profile in LC. The potential role of chair-side aMMP-8 POCT for screening oral inflammation in this population merits further investigation.

Graphical Abstract​

Highlights​

• Long COVID patients showed higher total MMP-8, MMP-9, TIMP-1, and MMP-9/TIMP-1 molar ratio.
• IFMA-measured active MMP-8 was independently associated with Long COVID.
• Chair-side aMMP-8 showed a non-significant trend towards higher positivity in LC.
• BMI was positively associated with oral MMP-8 and MMP-8/TIMP-1 molar ratios.
• These findings support further evaluation of chair-side aMMP-8 POCT in LC

Web | DOI | International Journal of Infectious Diseases

 

[V.R.T.]

MMP-9 in two studies from Klimas' group

Long COVID elevated MMP-9 and release from microglia by SARS-CoV-2 Spike protein
Duraisamy Kempuraj; Irene Tsilioni; Kristina K. Aenlle; Nancy G. Klimas; Theoharis C. Theoharides

OBJECTIVES
Long COVID is a major health concern because many patients develop chronic neuropsychiatric symptoms, but the precise pathogenesis is unknown. Matrix metalloproteinase-9 (MMP-9) can disrupt neuronal connectivity and be elevated in patients with long COVID.

METHODS
In this study, MMP-9 was measured in the serum of long COVID patients and healthy controls, as well as in the supernatant fluid of cultured human microglia cell line stimulated by recombinant severe acute respiratory syndrome coronavirus 2 Spike protein, as well as lipopolysaccharide (LPS) and neurotensin (NT) used as positive controls. MMP-9 was measured by commercial enzyme-linked immunosorbent assay.

RESULTS
MMP-9 was significantly elevated in the serum of long COVID patients compared to healthy controls. Moreover, there was significant release of MMP-9 from a cultured human microglia cell line stimulated by LPS, NT, or Spike protein. We further show that pretreatment with the flavonoids luteolin and tetramethoxyluteolin (methlut) significantly inhibited the release of MMP-9 stimulated by the Spike protein.

CONCLUSIONS
MMP-9 from Spike protein-stimulated microglia could contribute to the development of long COVID and may serve as a target for treatment including the use of luteolin.

Link | PDF (Translational Neuroscience) [Open Access]

Abstract​

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disease of unknown aetiology associated with chronic severe fatigue and neurological symptoms, including dizziness, sleep disturbances, cognitive impairment and pain. There are no reliable blood biomarkers available for ME/CFS, possibly due to the lack of specific pathogenesis, even though Epstein-Barr Virus (EBV) has been suspected.

We quantified the levels of IL-interleukin-11 (IL-11) in the serum of female ME/CFS patients (n = 40; mean age 51 years) and age- and gender-matched healthy control subjects (n = 38; mean age 43), as well as matrix metalloproteinase-9 (MMP-9) in ME/CFS patients (n = 18; mean age 57 years old ) and healthy control subjects (n = 18; mean age 53 years old), using an enzyme-linked immunosorbent assay (ELISA).

We hypothesized that mast cells (MC) stimulated by EBV may be involved.

MC are unique tissue immune cells that have been implicated in ME/CFS.

MC were grown from human umbilical cord blood CD34+ stem cells in vitro and incubated with recombinant (rEBV) protein, following which the release of MMP-9 was assayed in the cell culture supernatant media by ELISA.

There was a significant increase in serum levels of IL-11 and MMP-9 in ME/CFS patients compared to control subjects.
MCs stimulated by rEBV protein released a high amount of MMP-9 compared to control cells.
In conclusion, IL-11, MMP-9 and MCs may be involved in ME/CFS individuals.

Frontiers | Elevated serum levels of interleukin-11 and matrix metalloproteinase-9 in myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disease of unknown etiology associated with chronic severe fatigue and neurological symptoms...

www.frontiersin.org