Biology subjects

Maddipati, K. R.

Publications and source records attributed to Maddipati, K. R..

7 recordsLinked to original sources

bioRxiv2026

Long-chain Polyunsaturated Fatty Acids Mitigate In Vitro Skeletal Muscle Wasting Induced by Colorectal Carcinoma Cells via a 15-LOX-dependent Pathway

Up to 50% of adults with colorectal cancer (CRC) are at risk of progressive involuntary loss of skeletal muscle mass and function known as cachexia. Available options to prevent and treat cachexia in cancer survivors are currently limited. Long-chain polyunsaturated fatty acids (LC-PUFAs) and their bioactive metabolites, termed specialized pro-resolving lipid mediators (SPMs), promote the resolution of inflammation and support muscle growth and repair. However, prior studies of cachexia have mainly focused on fish oil supplements, and it is not fully understood how different individual omega-3 (n-3) and omega-6 (n-6) LC-PUFAs mediate CRC-induced muscle wasting. In addition, the crosstalk between cancer cells, the host immune system, and skeletal muscle cells in response to LC-PUFA treatments remains unclear. This study aimed to examine the effects of n-3 and n-6 LC- PUFAs on CRC-induced muscle wasting and the underlying cellular and molecular mechanisms involved. Using murine C2C12 skeletal muscle cells and CT26 colorectal carcinoma cells, we investigated the impacts of LC- PUFAs including arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid (DPA, 22:5n-3), and docosahexaenoic acid (DHA, 22:6n-3) on CT26-induced muscle cell wasting in the presence or absence of lipoxygenase (LOX) inhibitors such as NDGA or BLX-3887. We also examined the lipidomic profile of C2C12-CT26 co-cultures in response to individual LC-PUFA treatments. Our results suggest that LC- PUFAs including ARA, EPA, DHA, and DPA each individually protect against CRC-induced muscle cell wasting in vitro, and these protective effects are dependent on 15-LOX activity. Furthermore, we found that C2C12-CT26 co-culture produced mature SPMs in response to individual PUFA treatments. Taken together, this study suggests that individual n-3 and n-6 LC-PUFAs can mitigate CRC-associated cachexia primarily by producing 15-LOX- derived bioactive lipid mediators.

cancer biology↗

bioRxiv2025

Leukocyte-type 12/15-lipoxygenase is essential for timely inflammation-resolution and effective tissue regeneration following skeletal muscle injury

Unlike traditional anti-inflammatory therapies which may interfere with musculoskeletal tissue repair, pharmacological administration of specialized pro-resolving lipid mediators (SPMs) can promote timely resolution of inflammation while stimulating skeletal muscle regeneration. Despite this, the potential role of endogenous inflammation-resolution circuits in skeletal muscle injury and repair remains unknown. Here, we investigated the effect of whole-body knockout of leukocyte-type 12/15-lipoxygenase (12/15-LOX) on acute inflammation and regeneration following skeletal muscle injury in mice. Prior to muscle injury, Alox15-/- mice displayed lower intramuscular concentrations of 12/15-LOX-derived lipid mediators than wild type (WT) mice, and this was associated with chronic low-grade muscle inflammation. Alox15-/- mice mounted an exaggerated acute immune response to sterile skeletal muscle injury which was associated with a local imbalance of pro-inflammatory vs. pro-resolving lipid mediators. During the regenerative phase, Alox15-/- mice displayed defects in myogenic gene expression, myofiber size, and myonuclear accretion. Mechanistically, bone marrow-derived macrophages (M[FE]) obtained from Alox15-/- mice produced less 12/15-LOX-derived lipid mediators and this was associated with impaired M2 polarization. Isolated myogenic progenitor cells also produced many LOX metabolites in response to long chain polyunsaturated fatty acid (LC-PUFA) supplementation, including bioactive SPMs. Alox15-/- myoblasts were both impaired in their ability to produce SPMs and were insensitive to the stimulatory effect of LC-PUFAs on in vitro myogenesis. These data show that the 12/15-LOX pathway is essential for timely resolution of acute inflammation and direct determination of myogenic progenitor cell fate following skeletal muscle injury.

developmental biology↗

bioRxiv2023

Inhibition of type III secretion system induced leukotriene B4 production by Yersinia pestis: A mechanism for early immune evasion

Subverting the host immune response to inhibit inflammation is a key virulence factor of Yersinia pestis. The inflammatory cascade is tightly controlled via the sequential action of lipid and protein mediators of inflammation. Because delayed inflammation is essential for Y. pestis to cause lethal infection, defining the mechanisms used by Y. pestis to manipulate the inflammatory cascade is necessary to understand this pathogens virulence. While previous studies have established that Y. pestis actively inhibits the expression of host proteins that mediate inflammation, there is currently a gap in our understanding of inflammatory lipid mediator response during plague. Here we use in vivo lipidomics to define the synthesis of lipid mediators of inflammation within the lungs during pneumonic plague. Interestingly, while we observed an early cyclooxygenase response during pneumonic plague, there was a significant delay in the synthesis of leukotriene B4 (LTB4), a pro-inflammatory lipid chemoattractant and activator of immune cells. Furthermore, in vitro studies with primary leukocytes from mice and humans further revealed that Y. pestis actively inhibited the synthesis of LTB4. Finally, using Y. pestis mutants in the Ysc type 3 secretion system (T3SS) and Yersinia outer protein (Yop) effectors, we demonstrate that leukocytes recognize the T3SS to initiate the synthesis of LTB4 rapidly. However, the Yop effectors secreted through the same system effectively inhibit this host response. Together, these data demonstrate that Y. pestis actively inhibits the synthesis of LTB4, an inflammatory lipid, required for rapid recruitment of leukocytes to the site of infection. Author SummaryYersinia pestis, the bacteria that causes plague, targets the hosts innate immune response to inhibit inflammation. Because the generation of this non-inflammatory environment is required for infection, we are interested in mechanisms used by Y. pestis to block inflammation. Lipid mediators are potent signaling molecules that regulate multiple host immune responses, including inflammation. While there have been studies on how Y. pestis blocks the proteins that mediate inflammation, there is a gap in our understanding of the inflammatory lipid mediator response during plague. Here we show that Y. pestis inhibits the production of one of these critical lipid mediators, leukotriene B4, by host immune cells. Furthermore, we identify both the signals that induce LTB4 production by leukocytes and the mechanisms used by Y. pestis to inhibit this process. Together, these data represent the first comprehensive analysis of inflammatory lipids produced during plague and improve our current understanding of how Y. pestis manipulates the host immune response to generate a permissive non-inflammatory environment required for bacterial colonization.

microbiology↗

bioRxiv2022

Maresin 1 Repletion Improves Muscle Regeneration After Volumetric Muscle Loss

The acute traumatic or surgical loss of skeletal muscle, known as volumetric muscle loss (VML), is a devastating type of injury that results in exacerbated and persistent inflammation followed by fibrosis. The mechanisms that mediate the magnitude and duration of the inflammatory response and ensuing fibrosis after VML remain understudied and as such, the development of regenerative therapies has been limited. To address this need, we profiled how lipid mediators, which are potent regulators of the immune response after injury, varied with VML injuries that heal or result in fibrosis. We observed that non-healing VML injuries displayed increased pro-inflammatory eicosanoids and a lack of pro-resolving lipid mediators. Treatment of VML with a pro-resolving lipid mediator synthesized from docosahexaenoic acid, called Maresin 1, ameliorated fibrosis through reduction of neutrophils and macrophages and improved myogenesis, leading to enhanced recovery of muscle strength. These results expand our knowledge of the dysregulated immune response that develops after VML and identify a novel immuno-regenerative therapeutic modality in Maresin 1.

physiology↗

bioRxiv2021

Local Shifts in Inflammatory and Resolving Lipid Mediators in Response to Tendon Overuse

Tendon inflammation has been implicated in both adaptive connective tissue remodeling and overuse-induced tendinopathy. Lipid mediators control the initiation and resolution of inflammation, but their roles within tendon are largely unknown. Here we profiled local shifts in intratendinous lipid mediators via liquid chromatography-tandem mass spectrometry in response to synergist ablation-induced plantaris tendon overuse. Sixty-four individual lipid mediators were detected in homogenates of habitually loaded plantaris tendons from healthy ambulatory rats. This included many bioactive metabolites of the cyclooxygenase (COX), lipoxygenase (LOX), and epoxygenase (CYP) pathways. Synergist ablation induced a robust inflammatory response at day 3 post-surgery characterized by epitenon infiltration of polymorphonuclear leukocytes (PMNs) and macrophages (M{Phi}), heightened expression of inflammation-related genes, and increased intratendinous concentrations of the pro-inflammatory eicosanoids thromboxane B2 (TXB2) and prostaglandin E2 (PGE2). By day 7, M{Phi} became the predominant myeloid cell type in tendon and there were further delayed increases in other COX metabolites including PGD2, PGF2 and PGI2. Specialized pro-resolving mediators (SPMs) including protectin D1 (PD1) and resolvin D6 (RvD6), as well as related pathway markers of D-resolvins (17-HDoHE), E-resolvins (18-HEPE) and lipoxins (15-HETE) were also increased locally in response to tendon overuse, as were many anti-inflammatory fatty acid epoxides of the CYP pathway (e.g. EpETrEs). Nevertheless, intratendinous prostaglandins remained markedly increased even following 28 days of tendon overuse together with a lingering M{Phi} presence. These data reveal a delayed and prolonged local inflammatory response to tendon overuse characterized by an overwhelming predominance of pro-inflammatory eicosanoids and a relative lack of pro-resolving lipid mediators.

immunology↗

bioRxiv2020

Lipidomic Profiling Reveals an Age-Related Deficiency of Skeletal Muscle Proresolving Mediators that Contributes to Maladaptive Tissue Remodeling

Chronic inflammation and deregulated acute immune cell responses to injury contribute to age-associated skeletal muscle dysfunction. Specialized pro-resolving mediators (SPMs) control inflammation and support myofiber regeneration in young mice, but their role in aging muscle remains unknown. Here we examined the effect of age on the mediator lipidome of skeletal muscle via LC-MS based lipidomic profiling and tested whether systemic administration of the SPM resolvin D1 (RvD1) could limit excessive inflammation and improve the regenerative capacity of aged muscle. Aged mice displayed chronic low-grade muscle inflammation prior to injury and this was associated with a basal deficiency of lipoxygenase (LOX) derived SPMs as well as anti-inflammatory cytochrome P450 (CYP) derived lipid epoxides. Following muscle damage, young and aged mice produced similar amounts of pro-inflammatory cyclooxygenase (COX) and 12-LOX metabolites, but aged mice mounted a markedly deficient SPM response. This was associated with heightened leukocyte recruitment, impaired myofiber regeneration, and delayed recovery of strength. Systemic treatment with RvD1 had minimal impact on excessive myeloid cell infiltration and defective myofiber regeneration in aged mice. Nevertheless, RvD1 treatment did suppress inflammatory cytokines, modulated muscle stem cells, limited maladaptive tissue remodeling, and improved recovery of specific muscle force. We conclude that aging results in a marked deficiency of local SPM biosynthesis within muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on myofiber regeneration of traditional anti-inflammatory treatments.

immunology↗

bioRxiv2020

Immunoresolvents Support Skeletal Myofiber Regeneration via Actions on Myeloid and Muscle Stem Cells

Specialized pro-resolving mediators (SPMs) actively limit inflammation and expedite its resolution. Here we profiled intramuscular lipid mediators following injury and investigated the role of SPMs in skeletal muscle inflammation and repair. Both eicosanoids and SPMs increased following myofiber damage induced by intramuscular injection of barium chloride or functional overload. Daily systemic administration of resolvin D1 (RvD1) limited the degree and duration of inflammation, enhanced regenerating myofiber growth, and improved recovery of muscle strength. RvD1 suppressed inflammatory cytokines, enhanced polymorphonuclear cell clearance, modulated muscle stem cells, and polarized macrophages to a more pro-regenerative subset. RvD1 had minimal direct impact on in-vitro myogenesis but directly suppressed myokine production and stimulated macrophage phagocytosis, showing that SPMs influence modulate both infiltrating myeloid and resident muscle cells. These data reveal the efficacy of immunoresolvents as a novel alternative to classical anti-inflammatory interventions in the management of muscle injuries to modulate inflammation while stimulating tissue repair.

immunology↗