Clinically relevant redifferentiation of fibroblast-like chondrocytes into functional chondrocytes by the low molecular weight fraction of human serum albumin.

OBJECTIVES: Traumatic joint injury induces chondrocyte dysfunction and progressive breakdown of articular cartilage, leading to post-traumatic osteoarthritis (PTOA). In this condition, dysfunctional fibroblast-like chondrocytes (FLCs) no longer express proteins required for cartilage maintenance, such as SOX9 and collagen-type II (COL2). Interleukin-6 (IL-6) has been demonstrated to downregulate expression of these two critical proteins in chondrocytes, and increased IL-6 levels have been measured in patients with PTOA. The <5kDa fraction of human serum albumin (LMWF5A) has been suggested to modulate this pathway, as decreased levels of IL-6 are secreted by immunostimulated LMWF5A-treated macrophages. Our objective was to determine whether LMWF5A induces an in vitro model of FLCs to redifferentiate into functional chondrocytes. METHODS: SOX9 and COL2 were monitored via western blot, and COL2 was detected with immunofluorescence. Aggrecan and IL-6 were quantified by ELISA. Glycosaminoglycan (GAG) levels were quantified with alcian blue. RESULTS: We found that LMWF5A significantly increases the principal cartilage transcription factor SOX9 and the SOX9 target protein COL2 in monolayer-cultured FLCs. Multiple LMWF5A treatments of 3-D pellet FLC cultures over 2wks resulted in a significant decrease in IL-6 and significant increases in the major players of articular cartilage mechanics, aggrecan and highly-sulfated GAGs. CONCLUSIONS: These data support the hypothesis and clinical outcomes of two phase III clinical trials that LMWF5A-treatment induces chondrogenesis and supports functional cartilage. We propose that LMWF5A could maintain articular cartilage integrity in all joints following traumatic injury.

The low molecular weight fraction of commercial human serum albumin induces acetylation of α-tubulin and reduces transcytosis in retinal endothelial cells.

It has long been appreciated that the microtubule network plays a critical role in endothelial cell function. Chemical inhibition of tubulin polymerization has been shown to drastically increases endothelial permeability via interactions with the actin cytoskeleton. Conversely, stabilization of microtubules significantly decreases vascular permeability. The purpose of this investigation was to determine if the low molecular weight fraction of commercial 5% human serum albumin (LMWF5A) alters endothelial cell cytoskeletal dynamics and function. To investigate this, human retinal endothelial cells (HREC) were treated with LMWF5A and the acetylation of α-tubulin was determined by immunofluorescent staining and immunoblotting. In addition, permeability assays were performed to evaluate functional changes. We found that HREC treated with LMWF5A exhibit a rapid increase in the amount and distribution of acetylated α-tubulin. This was accompanied by a reduction in macromolecular permeability. Calcium depletion and inhibition of PI3-kinase reduced LMWF5A-induced acetylation while p38 MAPK inhibition potentiated this effect. These findings suggest that LMWF5A mediates changes in the microtubule network and reduces transcytosis in HREC.

The low molecular weight fraction of human serum albumin upregulates production of 15d-PGJ2 in Peripheral Blood Mononuclear Cells.

Activation of the innate immune system involves a series of events designed to counteract the initial insult followed by the clearance of debris and promotion of healing. Aberrant regulation can lead to systemic inflammatory response syndrome, multiple organ failure, and chronic inflammation. A better understanding of the innate immune response may help manage complications while allowing for proper immune progression. In this study, the ability of several classes of anti-inflammatory drugs to affect LPS-induced cytokine and prostaglandin release from peripheral blood mononuclear cells (PBMC) was evaluated. PBMC were cultured in the presence of dexamethasone (DEX), ibuprofen (IBU), and the low molecular weight fraction of 5% albumin (LMWF5A) followed by stimulation with LPS. After 24 h, TNFα, PGE2, and 15d-PGJ2 release was determined by ELISA. Distinct immunomodulation patterns emerged following LPS stimulation of PBMC in the presence of said compounds. DEX, a steroid with strong immunosuppressive properties, reduced TNFα, PGE2, and 15d-PGJ2 release. IBU caused significant reduction in prostaglandin release while TNFα release was unchanged. An emerging biologic with known anti-inflammatory properties, LMWF5A, significantly reduced TNFα release while enhancing PGE2 and 15d-PGJ2 release. Incubating LMWF5A together with IBU negated this observed increased prostaglandin release without affecting the suppression of TNFα release. Additionally, LMWF5A caused an increase in COX-2 transcription and translation. LMWF5A exhibited a unique immune modulation pattern in PBMC, disparate from steroid or NSAID administration. This enhancement of prostaglandin release (specifically 15d-PGJ2), in conjunction with a decrease in TNFα release, suggests a switch that favors resolution and decreased inflammation.

The low molecular weight fraction of human serum albumin upregulates COX2, prostaglandin E2, and prostaglandin D2 under inflammatory conditions in osteoarthritic knee synovial fibroblasts.

BACKGROUND: The ability to decrease inflammation and promote healing is important in the intervention and management of a variety of disease states, including osteoarthritis of the knee (OAK). Even though cyclooxygenase 2 (COX2) has an established pro-inflammatory role, evidence suggests it is also critical to the resolution that occurs after the initial activation phase of the immune response. In this study, we investigated the effects of the low molecular weight fraction of 5% human serum albumin (LMWF-5A), an agent that has proven to decrease pain and improve function in OAK patients after intra-articular injection, on the expression of COX2 and its downstream products, prostaglandins (PGs). METHODS: Fibroblast-like synoviocytes from the synovial membrane of OAK patients were treated with LMWF-5A or saline as a control with or without the addition of interleukin-1ß (IL-1ß) or tumor necrosis factor α (TNFα) to elicit an inflammatory response. Cells were harvested for RNA and protein at 2, 4, 8, 12, and 24 h, and media was collected at 24 h for analysis of secreted products. COX2 mRNA expression was determined by qPCR, and COX2 protein expression was determined by western blot analysis. Levels of prostaglandin E2 (PGE2) and prostaglandin D2 (PGD2) in the media were quantified by competitive ELISA. RESULTS: In the presence of either IL-1ß or TNFα, LMWF-5A increased the expression of both COX2 mRNA and protein, and this increase was significant compared to that observed with IL-1ß- or TNFα-stimulated, saline-treated cells. Downstream of COX2, the levels of PGE2 were increased only in TNFα-stimulated, LMWF-5A-treated cells; however, in both IL-1ß- and TNFα-stimulated cells, LMWF-5A increased the release of the anti-inflammatory prostaglandin PGD2. CONCLUSION: LMWF-5A appears to trigger increased anti-inflammatory PG signaling, and this may be a primary component of its therapeutic mode of action in the treatment of OAK.

A unique C-terminal repeat domain maintains the cytosolic localization of the placenta-specific tristetraprolin family member ZFP36L3.

Members of the tristetraprolin family of CCCH tandem zinc finger proteins bind to AU-rich elements in certain cellular mRNAs, leading to their deadenylation and destabilization. Studies in knock-out mice demonstrated roles for three of the family members, tristetraprolin, ZFP36L1, and ZFP36L2, in inflammation, chorioallantoic fusion, and early embryonic development, respectively. However, little is known about a recently discovered placenta-specific tristetraprolin family member, ZFP36L3. Tristetraprolin, ZFP36L1, and ZFP36L2 have been shown to shuttle between the nucleus and cytoplasm, using typical hydrophobic amino acid-rich nuclear export sequences, and nuclear localization sequences located within the tandem zinc finger domain. In contrast, we previously showed that green fluorescent protein-labeled ZFP36L3, expressed in HEK 293 cells, remained cytosolic, even in the presence of the nuclear export blocker leptomycin B. We show here that the conserved tandem zinc finger domain contains an active nuclear localization signal. However, the sequence corresponding to the nuclear export signal in the other family members was nonfunctional, and thus did not contribute to the cytosolic localization. The unique C-terminal repeat domain could override the activity of the nuclear localization sequence, preventing the import of ZFP36L3 into the nucleus. Immunostaining of mouse placenta demonstrated that ZFP36L3 was located only in the cytoplasm of trophoblast cells. Thus, in contrast to the other mammalian members of this protein family, ZFP36L3 is a "full-time" cytosolic protein, rather than a nucleocytoplasmic shuttling protein. The significance of this difference in subcellular localization to the physiology of placental trophoblast cells, where ZFP36L3 is selectively expressed, remains to be determined.

Flanking sequences modulate diepoxide and mustard cross-linking efficiencies at the 5'-GNC site.

Diepoxybutane, diepoxyoctane, and mechlorethamine are cytotoxic agents that induce interstrand cross-links between the N7 positions of deoxyguanosine residues on opposite strands of the DNA duplex preferentially at 5'-GNC sequences. We have systematically varied the identity of either the base 5' to the cross-linked deoxyguanosine residues or the intervening base pair to determine flanking sequence effects on cross-linking efficiency. We used synthetic DNA oligomers containing four 5'-N(1)GN(2)C sites that varied either N(1) or N(2). Interstrand cross-links were purified through denaturing polyacrylamide gel electrophoresis and then subjected to piperidine cleavage. The amount of cleavage at each deoxyguanosine residue, representative of cross-linking efficiency at that site, was determined by sequencing gel analysis. Our data suggest that cross-linking efficiency varies with the identity of N(1) similarly (purines > pyrimidines) for diepoxybutane, diepoxyoctane, and mechlorethamine but that the effects of N(2) differ for the three compounds.